Antioxidant Supplements – Are They Needed?

Everyday it seems that new supplements are appearing on the market. One group of nutritional supplements that has received a lot of attention in the past few years is antioxidants. Vitamins such as C, E and beta-carotene along with fruits like blueberries and strawberries are considered powerful antioxidants. Some claim that these have many health benefits including enhanced exercise performance. Is this true? Can antioxidants benefit athletes? Dr. Scott Powers of the University of Florida is one of the leading researchers on exercise and antioxidants. He has published a review article focusing on antioxidant supplementation and performance. In his review, he concludes that there is actually little scientific evidence in favor of supplementation and that supplementation with high doses may do more harm than good.

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What exactly are antioxidants? Antioxidants are a class of compounds that fight off reactive oxygen. Chemically speaking, reactive oxygen (or oxygen radicals) is formed when oxygen molecules lose an electron. This makes the molecule highly unstable and reactive. These molecules can then damage proteins, membranes and DNA. Such “oxidative damage” can lead to cell death, and is linked to many disorders including some cancers. Antioxidants scavenge reactive oxygen and protect cells from damage.

Reactive oxygen is formed during the normal course of metabolism. Some conditions lead to greater production and a condition known as oxidative stress occurs. Cells are equipped with its own antioxidant defenses so that most conditions of oxidative stress are easily handled by the cell. In some pathological conditions, oxidative stress can be very large greater or the cells own antioxidant defenses are suspect. Under either these conditions, reactive oxygen accumulates and the damaging to various cells can be severe.

During exercise, metabolism increases 10-20 times normal. As a result, the muscle cells undergo a period of oxidative stress and there is a rise the in amount of reactive oxygen produced. However, this rise is relatively small and very temporary compared to clinical conditions. Nevertheless, some researchers have linked this exercise-induced oxidative stress to exercise performance. They feel that it plays a key role in fatigue during prolonged activity lasting more than 30 minutes. By providing greater defense against reactive oxygen through supplementation, fatigue can be delayed.

On the other hand, many researchers point out that normal, healthy individuals have more than enough natural antioxidants to protect against oxygen radicals. This is especially true during exercise. Enzymes and antioxidant compounds found within muscle cells are more than capable of fighting off reactive oxygen. In fact, one of the benefits of exercise training is enhanced protection against oxidative stress – training builds greater defense. This adaptation leads this group to argue that reactive oxygen plays little if any role in the development of fatigue.

Given this debate, will do antioxidant supplements improve exercise performance?

The compound N-acetylcystine (NAC) may have some positive effects on performance. A few laboratory studies show that NAC delays fatigue under some conditions. Unfortunately, the methods used in these studies raise questions about the practicality of using NAC. For instance, one study shows positive effects after 35 minutes of intravenous infusion of NAC. Needles to say, most athletes cannot nor should not take such a pre-match approach. A few other studies show little or no effect of ingesting NAC on performance. So while there may be some potential for NAC to delay fatigue, there is not enough evidence to suggest that athletes use it as a performance enhancer.

As for nutritional antioxidants such as vitamins C, E or beta carotene, the research is much clearer. The vast majority of scientific studies show that supplementation with these vitamins has very little effect on performance. The vast majority of research studies all agree on this point. Further, a review of more than 68 clinical trials emphasize that dietary supplementation with these vitamins does not appreciably improve health. As it turns out, a well balanced diet that is high in fresh fruits and vegetables provides plenty of antioxidants and little benefits are gained by supplementation.

In his review, Dr. Powers emphasizes an important point. New evidence indicates combating exercise-induced oxidative stress may actually do more harm than good. Reactive oxygen seems to trigger the muscle to adapt to training. The brief rise during exercise stimulates the muscle to produce the machinery needed to improve function (and to combat oxidative stress). This includes muscle proteins as well as mitochondria and enzymes needed for energy production. Two recent studies emphasize this point. Both show that supplementing the diet with large amounts of vitamin E and C (~16 times the RDA for an adult) blunt the training adaptation to exercise.

The bottom line is that antioxidant supplements are not needed for otherwise healthy athletes who have solid nutritional habits. The only exception is athletes who do not eat a proper diet. Those who skip meals, don’t eat proper servings of fruits and vegetables or try to lose excess weight by cutting calories may benefit from a vitamin supplement that contains antioxidants. Otherwise, a healthy diet will provide more than adequate defense against oxidative stress and allow training adaptations. Supplementing the diet with antioxidants will not provide an added training benefit.

Finally, it should be pointed out that nearly all of the studies addressing the ability of antioxidants to improve performance were carried out with adult subjects. There is little if any research on adolescents or pre-adolescents. This makes it even more difficult to recommend antioxidant supplements to young athletes. Neither the positive nor potentially negative effects of short- or long-term use are understood. Thus, at this time, young players should focus on proper nutrition rather than supplement use.

Reference:

Stear SJ, Burke LM, Castell LM, Powers SK, Kavazis AN, Nelson WB, Ernst E (2009) BJSM Reviews: A-Z of nutritional supplements, sports nutrition foods and ergogenic aids for health and performance Part 3. British Journal of Sports Medicine, 43:890-892.
Posted by Jay Williams, Ph.D. Labels: Current Research, Nutrition, Supplements

Recreational Soccer: The Magic Pill for Adult Health?

Many adults are engaged in a never ending search for the “magic pill” that will improve their health and wellbeing. This is the focus of many fitness products and nutritional supplements that advertise extraordinary gains in health with little effort. Others spend countless hours pound away on the treadmill, stationary bicycle or elliptical machine in an effort to lose weight, improve fitness and avoid health complications. While we may never find that magic pill we may have found a balance between monotonous exercise and the lure of a quick fix. A recent research review argues that sedentary adults who participate in recreational soccer programs reap the same benefits as those who engage in more traditional exercise routines.

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This post focuses on a review article by researchers at the University of Copenhagen. The article is a part a special issue of the Scandinavian Journal of Medicine and Science in Sports that is devoted to the health benefits of soccer. In weeks to come, we will be discussing other articles in this journal. For now, the focus is on adults and recreational soccer programs.

The researchers analyzed research studies focused on the health and fitness effects of recreational soccer. The approach they took was rather unique. Most agree that placing sedentary adults in ANY type of exercise program, including recreational soccer, will improve fitness and other health markers. In this review, the Copenhagen researchers also compared the effects of soccer to the effects of other types of exercise, specifically jogging, interval running and strength training.

In general, the studies examined sedentary adult subjects who participated in recreational soccer programs. The ages of the subjects were not specifically listed but were identified as “adults”. Most of the available studies used male subjects but a few focused on women. The programs lasted between 10 and 24 weeks and subjects typically played 3 times per week for 30-60 min per session. Training session usually involved small-sided games but some used 11v11 matches.

What follows is a summary of the overall findings and conclusions.

Fitness: Subject engaged in soccer training improved their VO2max by an average of 13%. Improvements were made using both full- and small-sided matches. When compared to jogging or interval running programs of similar training hours, the improvements in fitness via soccer were similar.

Cardiovascular Effects: Soccer training lead to reductions in resting blood pressure and resting heart rate. The effects on blood pressure were most pronounced in subjects with the highest initial levels. In addition, the researchers concluded that the improvements have significant health effects for the participants such as reduced risk for stroke and heart attack.

Blood lipids were also improved through soccer training. LDL cholesterol (bad cholesterol) was lowered and HDL cholesterol (the good type) was elevated after training. In addition, improved glucose tolerance and muscle enzyme levels in Type II diabetic patients occurred when soccer training was combined with nutritional advice. All of the changes due to recreational soccer participation were similar to those found using other exercise programs.

Body Composition: The soccer training programs show small reductions in body fat and increase in lean body mass. The changes in lean body mass reflect increases in muscle mass and muscle fiber hypertrophy. Such changes are not normally seen after jogging or interval running. Muscle fiber hypertrophy observed after soccer training (~15%) was nearly the same as that seen after weight training in men of similar age (~18%). Soccer also elicited changes in neuromuscular control that may improve balance and reduce the risk of falls and joint injuries.

Bone Mass: A few studies found that bone health was improved after soccer training. Bone mass in the legs, hip and lumbar spine were all increased. The changes were much greater than those that occurred after jogging and interval running and similar to weight training.

Perceived Effort: Perhaps one of the most important findings was that ratings of perceived exertion during soccer training were lower than those recorded during running. That is, when exercising at similar work rates and intensities, soccer participants felt a reduced sense of effort – they didn’t perceive themselves as working as hard as the runners. This may be linked to factors such as the focus and enjoyment of playing soccer and the social interactions with teammates. The more participants enjoy their exercise program, the greater their level of participation and the greater the health benefits.

Injury Risk: On the downside, the risk of injury may be somewhat greater in soccer programs that in other exercise programs – especially given the movement patterns and potential for contact injury. However, this is a difficult comparison to make since many of the risk injury studies don’t consider the intensity of the program. The Copenhagen researchers calculated that in the all of the studies reviewed,

Reference:

Krustrup P, Aagaard P, Nybo L, Peterson J, Mohr M, Bangsbo J (2010) Recreational football as a health promoting activity: A topical review. Scandinavian Journal of Medicine and Science in Sports, DOI: 10.1111/j.1600-0838.2010.01108.x
Posted by Jay Williams, Ph.D. Labels: Health, Training

Should We Have Expected John Brooks’ Goal?

Yesterday in a thrilling match, US defender John Brooks scored in the 86th minute to secure a win over for the Americans over Ghana. The goal came off of a corner kick delivered by Graham Zusi. An exciting play for sure and a critical 3 points for the US. But, at this point in the World Cup competition should we have expected a goal to come from a corner kick?

In the 2010 World Cup, 627 corners were taken that resulted in 9 goals. That’s an average of one goal scored for every 70 corners attempted. Graham Zusi’s was the 126th corner taken so far in this year’s competition. Prior to the US goal, Switzerland and German scored the only goals from corner kicks. Add the US goal and we have 3 goals scored from 127 corners (Ghana had one CK after the US goal). That’s an average of 1 goal every 42.3 attempts. Slightly less than the 2010 average.

Based on the 2010 statistics, should we have expected the US to score? The average so far is about nine corner kicks per match so the next corner kick goal should have come about three matches later, not in this match. Given that stat, should the US have played a short corner and kept possession? Obviously not! They clearly made the right call. All statistics have some degree of randomness, outliers that occur outside of what is expected. And this is what makes the game so exciting – goals coming at unexpected times from unexpected players. In this case, John Brooks and Graham Zusi created their own outlier – an unexpected goal that earned the US the win.
Posted by Jay Williams, Ph.D.

Prepping for the World Cup

The 2014 World Cup is ready to kick-off. Four years of preparation for an event that demands players pay a heavy physical and psychological price for success. As fans and coaches, we’re excited when our team overachieves and secures unexpected points and advances to the next round. Unfortunately we’ve often seen our side underperform. They seem listless and lethargic for no particular reason, making rare and uncommon mistakes. Matches that should be easily won turn into losses. This is especially true during the critical times when multiple matches are played within a short span of time. Teams have trained on every aspect of the game and they are fit and ready to play. But is there something else needed for a team to play well? As it turns out, what teams do off the field and behind the scenes can impact success. On the Science of Soccer Online, we have talked about a congested calendar, recovery and refueling. In this post, I’d like to us the World Cup as a framework to briefly summarize four key issues: how diet, recovery, sleep and daily hassles can play critical roles in improving or undermining performance during the match. Links are included for additional info.

Fitness, technical and tactical abilities are clearly keys to winning in Brazil. However, matches can also be won or lost off the field. What should players expect when playing such a congested schedule? Each match requires a tremendous physical effort. During 2010, US midfielder Michael Bradley averaged ~8 miles per match sprinting, running, jogging and walking. Add to that, stops, starts, turns and jumps and the energy cost of a single match is quite high. If they make the finals, Brazil will play seven matches in 32 days. Belgium (Group H) would play seven matches in 27 days. To make things tougher, there are only three days of recovery between some matches. This is certainly the case as teams work their way through the knockout rounds on the way to the championship match. Given the physical demands and schedules faced, it will be important for teams think ahead in order to quickly recover and prepare for upcoming matches. This will help avoid injury and illness as well as performance.

Diet and Hydration: What types of foods and beverages should players eat and drink during the tournament? We’ve talked at length on the SSO and through the NSCAA about the need for high carbohydrates, about 60-70% of total calories. This remains true for the duration of the tournament – . However, given the amount of muscle damage that is likely to occur with repeated matches, it is also important to add additional protein to the daily diet. Pre-match suggestions hold true – a high carbohydrate meal 3-4 hours before kick off followed by high carbohydrate snacks as kick off approaches. The post-match recovery diet will be critically important. Players need to eat and drink plenty of carbohydrates soon after the final whistle. The key is the first 45-60 minutes – take in plenty of high carbohydrate foods and beverages along with a small amount of protein will “jump start” the recovery of muscle glycogen.

The climate in Brazil means that proper hydration will play center stage in the tournament. Because of the high temperatures, players will lose considerable amounts of fluid along with key minerals and electrolytes. Not only can dehydration affect performance, it can cause serious health issues and raise the risk of injury. Players should drink before, during (when possible) and after the match or training. Fluids need to be replaced on a daily basis. The rule of thumb is to drink 1.5 times the amount of fluid lost during the activity. Sports drinks can provide fluids, carbohydrates and minerals lost during training and matches.

Many players enjoy a cold beer or two after a match. There’s probably a psychological and social aspect to relaxing and having a beer with teammates. However, too much alcohol, especially liquor can increase muscle soreness and inhibit recover of muscle glycogen.

Recovery: Apart from the diet, what is the best way to physically recover from a match? There is no doubt that the intensity of the match will leave players with delayed onset muscle soreness. To limit soreness, a post-match cool down is essential. Also, light exercises the following day can help alleviate muscle soreness.

Two other strategies that we’ve discussed are ice baths and compression garments. Research into ice baths and massages is a bit confusing. Ice is thought to reduce muscle inflammation and massages are designed to stimulate blood flow and promote relaxation of sore muscles. Studies show differing results ranging from no effect to modest effects on soreness and subsequent performance. Much of the benefit of these treatments may be psychological, reducing the perception of pain rather than actually “healing” the muscle. Perhaps the mental relaxation of a massage alleviates the discomfort. In no case has research shown adverse effects of ice baths and massage. So, while the benefits may be small, there is certainly no harm.

Compression garments are often used by players during a match to improve performance and limit muscle injury risk. Worn after a match, compression garments may offer some benefit by preventing muscle pooling. They could be particularly effective on a long plane flight or bus ride after a match. As with ice and massage, the research is not conclusive regarding positive effects but show no ill effects. So, it’s reasonable to suggest that players use compression garments and err on the side of a positive effect.

Analgesics are one of the most prescribed medications at previous World Cups. Non-steroidal anti-inflammatory compounds like ibuprofen, aspirin and acetaminophen are commonly used to combat muscle soreness and other mild discomforts. We’ve warned against relying too heavily on these drugs as they may mask a serious, underlying injury. Hopefully each team has a competent medical staff that can evaluate minor aches and pains and prescribe proper treatment rather than players self-medicating themselves.

We’ve also talked previously about the use of antioxidants to combat muscle soreness. While these offer some support for recovery, they may blunt a training effect. It’s important to note that athletes at the World Cup are not in training during competition – it’s too late to make major improvements in fitness. Thus, use of antioxidant vitamin supplements may be beneficial in limiting muscle damage and soreness during the tournament without impacting fitness. Vitamin supplements are also recommended to avoid possible dietary deficiencies due to varied eating patterns, training, match and travel schedules that could lead to illness.

Rest and Sleep: Part of the recovery process in sleep. Both sleep quality and quantity can affect performance. And, the schedule of events, travel and training can impact sleep. Travel, especially across multiple time zones often disrupts sleep patterns. In the case of the Brazil World Cup, most matches will be played in a single time zone. Only two venues lie in a different zone. So, time changes should not be a major problem. However, distance and time spent travelling can be an issue. The US will log nearly 9,000 miles flying between group-stage matches in Sao Paulo, Natal, Manaus and Recife. Research has shown that as the distance traveled increases, sleep as well as physical and mental performance can be impacted. This is especially true when discussing home field advantage. Since all teams will be travelling and there are no true home venues (except for Brazil), it will be interesting to see if travel and sleep patterns affect one team more than another.

Daily Hassles: Daily hassles are those small disruptions to your day – issues that crop up and have to be dealt with. Travel is a major daily hassle. Packing and unpacking, unfamiliar surroundings, different dining patters all create frustrations. Add to that meetings with the press, communicating with family members, and treatment for injuries means that players can expect stress-filled days. As the number of daily hassles grows, performance decreases, mental focus suffers and injury risk increase. Add to that, variations in player psyche, and it’s easy to see how scheduling can affect the player. A key for the support staff of each team will be to limit these daily hassles and keep disruptions of the daily routine to a minimum.

Bottom Line: The fittest and more technically and talented team may not be the most likely to add a star the their nations badge. The Champions may be the team that performs best off the field. Those who are prepare properly behind the scenes to insure players are well fed and hydrated, undergo proper recovery, maintain set schedules and limit daily distractions may be the sides that challenge for the trophy. Remember, failing to prepare properly can distract and disrupt even the most gifted side.

Penalty Shootouts, Mostly a Head Game?

Penalty kicks, especially taken during a shootout are high-pressure situations. This is true for both the shot take and the goalkeeper. Success, for each player depends on several factors, physical and mental. Previous posts on the SSO talked about the role psychology plays during the penalty kick. The defending position of the keeper, confidence of the kicker and even jersey color may influence whether or not a shot is saved or a goal is scored. Two new research studies published in the Journal of Sports Science examined other possible factors affecting penalty kicks. These studies show that the goalkeeper’s movements before the shot is taken and the kicker’s reaction after a successful shot may influence shot success as well as the outcome of a shootout.
The first study asked the question, “Does goalkeeper movement before a penalty kick distract the kicker?” A group of university players were asked to take penalty shots while the goalkeeper either remained stationary or moved by waving his arms up and down before each attempt. The goalkeeper was asked to remain in the center of the goal until the ball was struck (that is, he was not to “guess” which direction to move)

A moving goalkeeper resulted in more shots saved. Slightly more than 8% of shots were saved with a stationary keeper while the moving keeper saved about 22%. With a moving keeper, more shots were placed in the center of the goal compared to the non-moving condition. The researchers also found that when the goalkeeper was moving, players found in more difficult to focus on the target or the ball. More attention was directed at the keeper when he was moving.

It appears that goalkeeper movement does indeed distract the penalty taker. Movement results in shots placed more in the center of the target and more easily saved. It should be pointed that this was a very controlled experiment in that players took multiple penalty shots (as opposed to a single shot taken during a shootout) and keepers were given specific instructions as to how to react to the shot. Nevertheless a moving goalkeeper may prove to be a successful tactic.

The authors quoted Bruce Grobbelaar, Liverpool keeper during the 1984 European Cup final. He said that his “spaghetti legs” strategy used during the shootout was not a way to disrespect the opponent but a way to test their concentration under pressure. In the end, Liverpool won and Grobbelaar was right – distracting the opponent does indeed test the confidence of the penalty taker.

The second study asked if the player’s reaction after a successful penalty kick affected the outcome of the shootout. The researchers focused on all of the penalty kick shootout during the 1974-2006 World Cups and the 1972 and 2008 European Championships (a total of 325 penalty kicks). They analyzed the each player’s reaction to a successfully kick. Displays of pride (arms raised, fist pumped, chest expanded), enjoyment / excitement (broad smile on the face) and other reactions such as looking downward were all recorded.

After scoring, 66% of the players displayed celebratory movements with their arms raised. Only two of the players displayed enjoyment with a wide smile. Those who showed the prideful behaviors were more likely to be on the wining team. The reactions most closely associated with wining the shootout were – one or both arms extended over the head, expanded chest and both hands clinched into fists. Interestingly, players who looked downward after a successful kick were less likely to be on the winning team. Thus, celebrations with displays of pride are linked to a successful shootout performance.

The researchers point out two possible reasons for the link between displays of pride and shootout success. First, players displaying prideful behaviors may instill confidence in their teammates and raise expectations of making their shot. This likely translates into successful attempts. Second, attitudes of pride and superiority may make their opponents feel inferior and less confident in their attempts, lowering their expectations of winning the shootout.

Whatever the underlying reasons, displays of pride during a shootout seem to have a positive effect on ultimate team performance. This leads the authors to suggest that penalty takers should celebrate a successful attempt as it may increase the likelihood of winning. However, they emphasize that celebrating with their teammates is the key to enhancing teammate confidence and success. “In your face” types of celebration directed at the opponents or celebrations directed to the audience may not be as effective.

So, are penalty kick shootouts a head game? These two studies suggest that there is a very strong psychological component. Goalkeeper movements before the shot seems to distract the shot taker and increase the probability of a save. Prideful player celebrations with the kicker’s teammates after a successful shot may raise the team confidence level and negatively influence the opponents. Either strategy may enhance the chances of winning a penalty kick shootout.

Reference:

Wood G, Wilson MR (2010) A moving goalkeeper distracts penalty takers and impairs shooting accuracy. Journal of Sports Sciences. 28:937-946.

Moll T, Jordet G, Pepping G-J (2010) Emotional contagion in soccer penalty shootout: Celebration of individual success is associated with ultimate team success. Journal of Sports Sciences. 28:983-992.
Posted by Jay Williams, Ph.D. Labels: Current Research, Goalkeepers, Psychology
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Halftime, Carbohydrates and a Re-Warm Up

Halftime of a soccer match is a short break between two periods of intense activity. It’s also a time for players to recover from the first period, re-hydrate, take in a few carbohydrates and a receive feedback and instructions from their coach. All squeezed into a 10-15 minute break. As such, different coaches may approach halftime differently. What is the best strategy for halftime? What should players do to recovery quickly and prepare themselves for the next period of play? Two recent studies shed some light on these questions. They give some insight on diet, hydration and physical activity practices that may help players maximize their second-half performance.

In the first study, Dr. Mark Russell and his colleagues looked at how carbohydrate ingestion during a match (sports drink) affects blood glucose (Russell et al., 2014). They found that drinking 150-200 ml (5-7 oz) before and every 15 minutes during the match and at halftime had a positive effect on blood glucose. But, this effect was found only at the end of the first period. During the second period, when blood glucose levels begin to wane, the carbohydrate drink had no effect.

Although carbohydrate is known to influence the physical proficiency and decision making of a player. So the recommendation is made to change the halftime food habit practices to enhance the player’s performance. Research is going on to find out alternatives to carbohydrate drinks which can provide more energy to the players. Click on imp source to read more about this.

One of the more interesting aspects of the study is the finding that blood glucose declined during the halftime break, despite the fact that the players drank a carbohydrate beverage five minutes into the 15-minute break. Thus, the players started the second period with fairly low blood glucose levels – not considered hypoglycemic, but close. Low blood glucose at the start of the second period could have a several negative impacts on their performance in the initial minutes. Slow, lethargic and fewer high intensity efforts are characteristic of low blood glucose.

Blood glucose during exercise and recovery is influenced by a number of factors. Insulin is a potent hormone that is released in response to high blood glucose. This promotes glucose uptake by fat and liver cells. Epinephrine (adrenalin) has the opposite effect, it stimulates the liver to break down its glycogen and release it into the blood as glucose. Cortisol has a similar effect. During exercise, especially intense exercise, epinephrine and cortisol levels in the blood are increased. In addition, insulin release is suppressed. This combination stimulates glucose release from the liver and prevents its uptake by fat cells. Thus, blood glucose levels are elevated. This provides the muscle with an ample supply of carbohydrate for its energy needs. In addition, hypoglycemia is prevented.

For the most part, the body views halftime as recovery. Things change during recovery. Within minutes of stopping exercise, epinephrine and cortisol levels subside and insulin levels rise. This stimulates glucose to move into the live (and muscle) to be stored as glycogen. When a carbohydrate sports drink is taken in and glucose enters the blood, the insulin response may be greater. This in turn, could lead to greater glucose uptake by the liver and reduced blood glucose or a “transient hypoglycemia”. This may be what happened during the halftime period of Dr. Russell’s study. In this case, the carbohydrate drink per se did not cause hypoglycemia, but it did not prevent the drop in glucose during recovery.

So, what should a player to do during halftime – drink carbohydrates or not? How can an athlete re-hydrate and replenish energy stores without sacrificing performance. Some insight might be gained from the second study.

This study focused on the benefits of a re-warm up during halftime (Edholm et al., 2014). During the 15-minute halftime of a competitive match, the researchers asked one-half of the players to take on a traditional passive recovery (control group). The other players were asked to rest for 7 minutes then do some low to moderate intensity jogging and calisthenics for the remaining 7 minutes (re-warm up group). In a second match, the players reversed their halftime strategy.

The researchers found that sprint and vertical jump performance declined during the first half. This was expected. However, during the 15-minute halftime interval, performance further declined in the control group but not in the re-warm up group. Thus, the re-warm up group was better prepared for the second period. Also, the re-warm up group maintained greater ball possession and had less defensive running than the control group. Thus a 7-minute, active re-warm up during halftime benefited player performance. Other studies have shown similar benefits of a re-warm up. In terms of match performance, it’s easy to envision how being physically ready to compete at the start of the second half could lead to a fast start and goal scoring opportunities.

One concern of an active re-warm up is that the amount of energy expended could impact performance later in the match. The researchers (and others) found that this is not the case. Seven minutes of low to moderate intensity activity had no negative impact on markers of fatigue such as running distance and intensity or exercising heart rate in the later stages of a match.

So, what do these two studies offer for a halftime strategy? Instead of having players enter “recovery mode” during halftime, they simply transition to and from a period of light activity. A key benefit of this approach to halftime might be suppression of insulin and maintenance of epinephrine. Combined, this could help the player maintain blood glucose levels, especially if he/she is taking in a carbohydrate beverage. Thus, the low blood glucose state that Dr. Russell found might be prevented by an active re-warm up. It should be pointed out that there is no research on combining a re-warm up AND sports drinks during halftime. So, this idea remains a bit untested.

As for a halftime strategy… First, blood glucose levels decline during the halftime recovery and this could affect performance at the start of the next period. Second, a halftime re-warm up seems to benefit performance, particularly at the start of the second period without negatively affecting the later stages of the match. It is possible that this effect is due, in part to maintaining blood glucose and avoiding the negative effects of hypoglycemia. Based on this, coaches should consider the following strategy. Provide the players with a carbohydrate beverage at the start of halftime. Have them rest and recover for the first few minutes while they begin drinking. Then, begin a low intensity re-warm up while they finish their drink. This should better prepare them for the second half compared to the traditional passive halftime. They should be ready for a fast start once the whistle blows. However, as with any new strategy, it’s always best to test this out on players during training and scrimmage matches. Sometimes, the theory doesn’t always translate into reality!

References:

Russell M, Benton D, Kingsley M (2014) Carbohydrate ingestion before and during soccer match play and blood glucose and lactate concentrations, Journal of Athletic Training, 49(4):447-453.

Edholm P, Krustrup P, Randers MB (2014) Half-time re-warm up increases performance capacity in male elite soccer players, Scandinavian Journal of Medicine and Science in Sports, in press, doi: 10.1111/sms.1223
Posted by Jay Williams, Ph.D.

Hamstring Strength, Fatigue and Knee Stability

The incidence of anterior cruciate ligament injuries is all too common. In the U.S., it is estimated that as many as 200,000 injuries occur per year. Most of these are non-contact, meaning that movements associated with activity (landing, stopping, turning and cutting) stress the ACL, causing it to rupture. Some also estimate that women are five to eight times more susceptible to ACL injury than their male counterparts. Over the past 20 years, we have begun to understand the mechanisms of these types of injuries as well as ways to reduce risk and prevent ACL tears.

ACL or anterior cruciate ligament is one one the most important ligament present in the knee. When the injury occurs the person can feel or hear a pop in the knee, the symptoms of swelling, pain and unable to take the upper body weight will happen. Depending on the severity the orthopedic doctor will suggest the treatment. my company gives you more insight into ACL.

A key risk factor is weak hamstring muscles. Weaker hamstrings increase risk. A new study shows that when hamstring strength is reduced by fatigue, the ACL is subjected increased stress, particularly when planting the foot and cutting. the study emphasizes the need for improving hamstring strength as an important means of lowering injury risk.

Seventeen active females performed a series of sidestep cutting maneuvers before and after undergoing a fatiguing bout of hamstring contractions. For the cutting maneuver, they were asked to run towards a force place, plant their right foot and cut to the side at a 45 degree angle. This was done several times. After the first round of trials, the subjects performed a series of hamstring contractions (hamstring curls) designed to induce fatigue and reduce hamstring strength. Afterwards, they repeated the cutting maneuvers.

The subjects were fitted with several joint markers and electrodes that were used to measure movements and muscle activity. Computer measurements of muscle activity, limb and joint movements were then entered into a three dimensional knee model to estimate loads placed on the ACL.

The figure (taken from the study) shows the load on the ACL during the sidestep cutting maneuver. When the foot touches the ground, ACL load increases, reaches a peak, then decreases at the athlete pushes off and the foot leaves the ground. The red line represents ACL load before the hamstring muscles were fatigued. The black line is the load immediately after. Notice the difference in peak force. The data show that when hamstring strength was reduced, the load on the ACL was increased by 36%. Most importantly, the forces exerted in the sagittal plane (viewed from the side as the tibia slides forward) and in the frontal plane (as the tibia undergoes knee valgus) were increased.

What seems to contribute to increased load on the ACL is decreased hamstring strength. During the cutting maneuver, peak forces produced by the hamstrings were reduced by 27%. With the hamstrings providing less force to stabilize the knee, the ACL has to shoulder more of the load.

The researchers also found that cutting while fatigued reduced the amount of hip, knee and ankle flexion. This in turn, increased the impact force as the foot hit the ground. This is, planting the foot with less hip, knee and ankle flexion causes it the “stop” more quickly, increasing impact. Increased impact forces add to joint stress and increase the load placed on the ligaments.

The key emphasis of the study is that when players execute a sidestep, cutting maneuver in a fatigued condition, weakened hamstring muscles can result in greater load placed on the ACL as well as higher joint impact forces. This increased load elevates risk of sustaining an ACL injury, possibly a ruptured or torn ligament.

We’ve known for years that weak hamstrings (especially relative to the quadriceps muscles) are a risk factor for ACL injures (link . While the hamstrings flex the knee joint, they also play an important role in stabilizing the knee and protecting the ACL. During a stopping or cutting maneuver, external forces along with the quadriceps muscle force can cause the tibia to slide forward, twist or undergo valgus movements (abduction or a knock-kneed position). This is referred to as “valgus collapse” and is one of the primary causes of non-contact ACL injury. The hamstrings are designed to counter these unwanted movements, pulling to tibia backwards and limiting rotation and valgus. Thus, weakened or fatigued hamstrings are less able to stabilize the knee and protect the ACL. As shown in the study, stress on the ACL is increased.

The take home message of this study is that strengthening the hamstrings and preventing fatigue should help stabilize the knee and prevent ACL injuries. It is this reason that ACL injury prevention training programs include strengthening the hamstring muscles. All of the programs advocated by trainers and therapists include some kind of hamstring exercises like the Nordic curls. By strengthening the hamstrings AND preventing them from fatiguing during a match, we may be able to reduce load placed on the ACL and lower the possibility of injury.

Research has clearly shown that ACL injury prevention programs such as the FIFA 11+ do help. Through persistent and diligent use of these programs, both the risk and incidence of injuries can be lowered (link, link, link). As mentioned earlier, more than 200,000 ACL injuries occur each year in the US. This is tremendous personal and financial burden. Also the potential for complications later in life such as osteoarthritis are high. Thus, any program that lowers injury risk should be strongly encouraged. In this case, an ounce of prevention is well worth a pound of cure.

Reference

Weinhandl JT, Earl-Boehm JE, Ebersole KT, Huddleston WE, Armstring BSR, O’Coner KM (2014) Reduced hamstring strength increases anterior cruciate ligament loading during anticipated sidestep cutting, Clinical Biomechanics, DOI: 10.1016/j.clinbiomech.2014.05.013.
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Labels: Current Research, Injuries, Training

Thursday, March 6, 2014 Balance, Fatigue and Carbohydrates

Over the past few years, coaches and researchers have been asking how balance affects different athletes. For sports such as gymnastics, the need for balance is obvious. In other sports like soccer, research shows that the ability to maintain balance also influences performance during cutting and changing directions. We also know that balance plays an important role in injury risk. Balance results as a response to various sensory inputs – both visual and mechanical. The central nervous system (CNS) processes this information then activates the appropriate muscles to reposition the body and/or to stabilize a joint. When the CNS cannot respond appropriately, players may fall or they may sprain or tear ligaments. Thus, a loss of balance is a key to players playing well and staying healthy. Two recent studies examined the relationship between fatigue and balance in young athletes. The first shows the extent to which fatigue disrupts balance while the second suggests that carbohydrates may be a solution to maintaining balance during a match.

In the first study, the researchers asked the question, how much does fatigue affects balance in young soccer players? Earlier studies looked at older, adult players but this is the first to focus on youth. The players were 14-15 year olds selected from competitive teams. Balance was measured by having the players stand on a pressure platform using one and two-legged stances. The pressure platform then measured “postural sway” – the degree and speed in which the athlete’s center of gravity swayed forward, backward, left and right. The greater the sway, the less balance exhibited by the player. The players did this before and after undergoing intense exercise designed to induce fatigue. For the fatigue protocol, the players were asked to go through several minutes of a moderate-intensity warm-up, and then perform six, 2 x 15 meter shuttle runs, separated by 20 seconds.

After exercise, the players’ balance was markedly disrupted. Regardless of which leg they stood on, their body swayed much more after fatigue than before. This was true for the amount of sway and how quickly they swayed to the front, back and side. In fact, the loss of balance was directly related to the degree of fatigue experienced – greater fatigue, more sway and less balance.

Similar to older, adult players, fatigue greatly affects balance in young soccer players. The authors point out that 14-15 year olds are still developing their proprioception and balance control systems. In these players, “neuromuscular immaturity”, weakness, fitness and training may also influence fatigue’s ability to disrupt balance. They go on to emphasize the role training plays in developing balance and avoiding injury in this age group.

The second study looked at young gymnasts (11-14 years old) and balance beam performance. The objective here was to determine how fatigue and a carbohydrate supplement affected the number of falls. One group of athletes underwent a warm-up followed by five sets of beam exercises. A second group participated in the warm-up plus 20 minutes of intense gymnastics training (designed to induce fatigue) before performing the five-set beam exercise. Shortly the beam routines, both groups of gymnasts were given either flavored water or a carbohydrate beverage.

As in the soccer study, fatigue affected balance by increasing the number of balance beam falls from 3.3 to 5.4 (63%). Interestingly, the carbohydrate supplement reduced falls regardless of the athlete’s level of fatigue. After intense exercise, falls were reduced to an average of 2.3. Without exercise, they were reduced to 1.9. Thus, a carbohydrate beverage can improve balance and balance beam performance in both fatigued and non-fatigued gymnasts.

What is interesting about this study is that the gymnasts did not experience a decline in blood glucose (hypoglycemia) following the intense training bout. Hypoglycemia often accompanies fatigue and can have negative effects on performance where effort, motivation or motor skill is involved. In fact, we often attribute the positive effects of carbohydrates on either prevention or reversal of hypoglycemia. In this study, hypoglycemia did not occur. Nevertheless, the researchers attributed the reduction in falls with carbohydrates to improved focus and attention.

Previously on the SSO, we’ve discussed an interesting effect of carbohydrates on athletic performance. As it turns out, players may not need to actually ingest carbohydrate drinks to gain an advantage. A “rinse and spit” method can also improve performance. That is, swishing the beverage in mouth without actually ingesting it has a psychological effect on performance by improving effort and skill. It seems that there is a link between the mouth and the brain that is somehow stimulated by carbohydrates. In fact, brain imaging studies show that just the presence of carbohydrates in the mouth activates regions of the brain involved in reward and the regulation of motor activity. This may be what affected the gymnasts’ performances. Carbohydrates in the mouth stimulated the brain and improved focus, attention and/or motor skill leading to improved balance and fewer falls.

Back to the soccer players and their balance problems with fatigue. The authors of the first study point out that neuromuscular training programs that include balance, strengthening and plyometric exercises are the best option to increase balance and reduce injury risk (as well as improve performance). This is especially true in young athletes. However, if carbohydrate beverages can improve balance and reduce falls in fatigued gymnasts, one can assume that they would do the same in fatigued soccer players. Thus, carbohydrate drinks given before and during training or matches, may be an additional tool for preventing injuries. By affecting the brain, carbohydrates may restore balance, prevent unwanted joint movements and reduce the risk of sprains, ligament tears and falls.

We’ve known for years that carbohydrate beverages provide fuel and hydration, both of which affect performance. This added benefit, linking the mouth to the central nervous system may aid in maintaining balance. To be truthful, this idea hasn’t been studied in detail. However, it is food (or drink) for thought.

References

Massimilano P, Ibba G, Attene G (2014) Fatigue-induced balance impairment in young soccer players. Journal of Athletic Training, in press, doi: http://dx.doi.org/10.4085/1062-6050-49.2.12

Batatinha HAP, et al. (2013) Carbohydrate use and reduction in number of balance beam falls: implications for mental and physical fatigue. Journal of the International Society of Sports Nutrition, 10:32.

Chambers ES, Bridge MW, Jones DA (2009) Carbohydrate sensing in the human mouth: effects of exercise performance and brain activity. Journal of Physiology, 587: 1779-1994.
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Labels: Current Research, Injuries, Nutrition

NSCAA Convention Recap

Thanks to everyone who attended my session on the recovery diet. It was a full house with some very good questions from the audience and from the Twitter feed. I want to thank the NSCAA for inviting me and giving me a change to “bridge the gap” between science and performance.

Gatherings like these are places where you meet new people and learn new things. If you have noticed, a major topic that is being discussed in most such formal and non-formal events is the growth of crypto currencies and the trend of trading with bots. Bot trading might sound something like a concept straight out of a science fiction movie. But it became a reality several months ago. There have been so many advancements that the bots designed to act as the trader can learn and evolve. These are self-learning bots that can observe their decisions compare them with the market results and the real time market data and then improve each of the future decisions. So the strategy that is fed into the bot would improve over time. The trading bot might also learn to compare and pick the best features in order to take the decisions quickly and accurately. Such advanced bots are the bots designed for the future. They are in fact the bots that are also the most relevant for the present trading scenario. So in a market that is filled with trading bots of different types and different customisation options the bots with self-learning abilities are the ones that stand out. These are also the ones that end up making better profits than the other similar bots in the field.

The self-learning bots would also have a competitive edge when it comes to making decisions in the fluctuating markets. Market fluctuations are prone to occur all the time. The way the trader makes use of these fluctuations is what determines the success of the trader, the profits he makes. For this the trader should be able understand the market cycles in crypto markets. If you are a first time crypto trader, my review here talks about one such trading bot that works pretty well in changing market conditions and gives some good profits for the investors.

If you weren’t able to attend, a recording of my presentation can be found HERE.

Also, the PowerPoint slides that I used can be found HERE.

Posted by Jay Williams, Ph.D.

The Advantages of High-Intensity Interval Training

Soccer is a unique sport where the average player covers up to 7 miles per games by running forward, backward, and sideways. Intermittent sprints are quite frequent, with players performing them around every 90 seconds. Players may also change directions nearly 1,000 times a match. Whether it is walking, jogging, or sprinting, some type of movement is always occurring. Given that the length and intensity of movements are somewhat random, it is very difficult to make a fitness-training program that adequately mimics the physical demands that are required of a soccer match. Traditional methods of fitness training such as going on a long distance running do not mimic the physical demands of a match, and thus may not be the most effective training method for soccer players. A more progressive training regime that has been labeled as high-intensity interval training (HIIT) has become popular amongst athletes in order to increase their fitness capacity.

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This article was written by Jeremy Williams

Many sports scientists have classified it as a “hybrid” sport, in reference to it requiring training of both the aerobic and anaerobic energy systems. Maximal oxygen consumption or VO2max is generally considered the best indicator of an athlete’s aerobic capacity and his/her ability perform exercise for long periods of time (cardiorespiratory endurance). Athletes that are considered “elite”, typically have a higher VO2max than those who are less competitive. Professional male players have VO2max values above 60 ml O2/kg.min, whereas female college players average in the mid 50’s. Because of the aerobic demands of the sport, a high VO2max gives a soccer player a distinct fitness advantage allow for a better performance on the field, especially during the later stages of the match.

HIIT is a program whereby an individual performs several intense, near maximal bursts of anaerobic activity lasting between 30 seconds and four minutes. These bouts are separated by fixed periods of less-intense activity, which might include light jogging, walking, or even complete rest. An example would be, an individual that runs a 150-200-meter sprint at maximal intensity, followed by a 2-minute recovery period of light jogging or walking. This is then repeated 4-6 times until the workout is completed. Does this type of training actually work? Does HIIT improve VO2max in soccer players?

Does HIIT Work?

A number of research studies have shown that HIIT increases aerobic capacity in untrained individuals. In addition, studies are emerging that show important effects on trained athletes and soccer players. They show that VO2max is increased between 6-8%. An excellent example of how HIIT can improve fitness in soccer players is a study carried out by researchers at Willamette University in Oregon. They compared HIIT and endurance running during an “off season” training period. They were interested in determining which form of training is better for improving fitness. The HIIT group performed five-30 sec maximal sprints separated by 3.5-4.5 minutes of recovery. The other group underwent 40 minutes of continuous running at 80% of their aerobic capacity. Training was conducted twice per week for 5 weeks. In both groups, VO2max increased by 4%, from 50.7 to 52.7 mL O2/kg/min. Also, performance on the Yo-Yo intermittent endurance test was equally improved.

HIIT has also been compared to other forms of soccer fitness training. For example, a recent study found that both small-sided games and HIIT improve VO2max by 7-8%. In terms of match performance, HIIT also results in players spending more time engaged in high intensity running efforts.

Research also shows that repeated sprint performance and exercise economy are improved following HIIT. Both of these changes are important for the athlete. One could argue that soccer is essentially a 90 minutes test of repeated sprint performance. Thus, HIIT offers a very sport-specific training adaptation. An increase in exercise economy means that he or she is using slightly less energy when performing the same amount of work. Some think that HIIT may improve running and sprint mechanics leading to less wasted energy. Whatever the cause, improving exercise economy could lead to important energy savings over the course of a match.

Based on these research studies, it is clear that HIIT does indeed improve VO2max in soccer players. Also, HIIT improves other aspects of performance like exercise economy and repeated sprint performance. Each of these improvements would be expected to translate to increased performance on the pitch.

How Does HIIT Work?

VO2max is determined by two key physiological variables. The first is cardiovascular performance and the heart’s ability to deliver oxygen to the muscle. Stroke volume or how much blood the heart pumps per beat is key to oxygen delivery. The second variable is the muscle’s metabolic capacity or its ability to extract oxygen from the blood and use it to produce energy. Improvements in VO2max following endurance training typically result from a 50/50 combination of cardiovascular and muscle adaptations. However, HIIT seems to increase VO2max by improving the muscle without affecting the cardiovascular system. That is, muscle metabolism is increased while stroke volume remains relatively unchanged.

Within the muscle, mitochondria (called the powerhouses of the cell) are the most affected by HIIT. These structures, located inside each muscle fiber have the machinery needed to combine oxygen with fuels like glucose, glycogen and fat to energy. Research shows that HIIT stimulates the muscle to produce more mitochondria. This means that the muscles of HIIT-trained players are better able to use oxygen than their endurance-trained competitors. HIIT also leads to increased muscle glycogen and a slower rate of glycogen use during exercise. Muscle glycogen is a critical fuel source for the player. The ability to slow glycogen depletion could pay dividends later in the match.

Thus, while HIIT and traditional endurance training both accomplish the same goals, they do so in somewhat different ways. Endurance training improves both the cardiovascular system and muscle metabolism. On the other hand, HIIT seems to cause greater improvements in muscle metabolism.

Why Might HIIT Be Better?

The fact that HIIT improves muscle metabolism has important implications for the soccer player. Soccer players generally have very high cardiovascular function. However the start-and-stop, sprint-jog-run nature of a match places a high demand on the muscle’s aerobic and anaerobic energy systems. Since HIIT relies on repeated high intensity sprints, it is very likely that both of these energy systems are stressed. Thus, a training program that and simulates the movements and energy demands encountered during a match is important for the player. HIIT training should give him or her the ability to jump, start, stop and change directions more effectively during the end of a match when fatigue starts to set in.

The second key advantage of HIIT is the time commitment. In the Willamette University study, the HIIT athletes trained 20-25 minutes per session compared to almost twice that time for the endurance group. This, HIIT can be a more economical way to improve fitness. For teams that have limited practice time on the field, this can be a huge advantage. Being able to improve fitness with a lower time investment leaves more time to work on other technical and tactical aspects of the game.

Using HIIT

Dr. Martin Gibala at McMaster University suggests that a combination of HIIT and endurance training may be best. Substituting 15-25% of the traditional training volume with HIIT or incorporating 2-3 sessions per week. Obviously this routine depends on the time of year and whether players are in-season, pre- or off-season. A greater number of HIIT sessions can be used during the off- and pre-season when the emphasis in on developing fitness. While in-season training may use HIIT once per week to maintain fitness.

The bottom line is that, research shows that HIIT is an effective and economical way to improve aerobic capacity in soccer players. In fact, the effects of HIIT on the exercising muscle and the minimal time commitment may make this mode or training preferable to traditional endurance running.

Jeremy Williams is currently a graduate student at Florida State University and assistant with the women’s soccer team.

References

Dupont G, Akakpo K, Berthoin S (2004) The effect of in-season, high-intensity interval training in soccer players. Journal of Strength and Conditioning Research, 18: 584–589.

Gibala MJ, Jones AM (2013) Physiological and performance adaptations to high-intensity interval training. Nestle Nutrition Institute Workshop Series, 76:51-60

Gibala MJ, McGee SL (2008) Metabolic adaptations to short-term high-intensity interval training: A little pain for a lot of gain? Exercise and Sports Sciences Reviews, 36:58-63.

Helgerud J, Engen LC, Wisloff U, Hoff J (2001) Aerobic endurance training improves soccer performance. Medicine and Science in Sports and Exercise, 33: 1925-1931.

Impellizzeri FM, Marcora SM, Castagna C, Reilly T, Sassi A, Iaia FM, Rampinini E (2006) Physiological and performance effects of generic versus specific aerobic training in soccer players. International Journal of Sports Medicine, 27: 483-492.

Rowan AE, Kueffner TE, Stavrianeas (2012) Short duration high-intensity interval training improves aerobic conditioning of female college soccer players. International Journal of Exercise Science, 5: 232-238.

For more info on HIIT

High-Intensity, Sprint-Interval Training and Fitness

High Intensity Training, Fitness and Training Time

Posted by Jay Williams, Ph.D. Labels: Training