Friday, June 27, 2014

What Can The US Team Expect Over the Next Few Days?


The US World Cup team has completed its group play.  Perhaps better than expected but maybe not as well as hoped.  However, there’s no debate that the team gave everything it had, rising to meet the physical challenge of three matches over 10 days.  Michael Bradley once again led the tournament’s group stage covering an average of 12.7 km or 7.9 miles per match.  In the Germany match he covered 13.1 km (8.1 miles) and performed 59 sprints.  In fact, the US team out distanced the Germans 10.2 to 9.8 km per player.  Add to that, the difficulty of playing on a rain soaked pitch and it’s easy to imagine that the match extracted a heavy physical price on the players.  What can the US expect over the next few days?  After such a physical effort, how long will it take them to recover muscle strength, speed and power?

We can get an answer to these questions through recent research done at the University of Lille and LOSC Lille. Their sport science groups looked at physical performance, fatigue and muscle soreness during the 72 hours following professional matches. The matches were played as part of the team’s regular schedule and the players followed normal recovery and training routine during the study.

Video analyses of each match were used to measure the distance run, number of long (>5sec) and short (<5sec) sprints, changes in direction, jumps and tackles.  Before each match then again at 24, 48 and 72 hours after, the researchers measured vertical jump, sprint speed, power output, and hamstring strength.  They also examined blood levels of creatine kinase (CK) as a marker of muscle damage.  Lastly, they asked players about their perception of soreness.

During the match, players performed and average of 16 short sprints and 11 long sprints.  They also executed 12 hard changes in direction and 10 jumps.  In all players had 98.5 playing actions.  The researchers pointed out that there was a wide range between players.  For example, the playing actions of individual players ranged from 16 to 132.

Following the match, players reported muscle soreness and had elevated CK levels for up to 72 hours.  Soreness was apparent at 24 hours, peak at 48 and began to subside at the 72-hour mark. For more info on muscle soreness, click here.  

Also, vertical jump (power), sprint speed and hamstring strength was reduced throughout the 72 hour recovery. These changes are shown in the figure.  Strength and power were reduced by ~8% at 24 hours then started to recover.  Speed remained decreased by ~5% from 24 to 72 hours.   An interesting finding about hamstring strength is that strength of the dominant leg was reduced more than that of the non-dominant leg.

What match activities contributed to soreness and reduced performance during the recovery period?  The number of short sprints, hard changes in direction and number of tackles were most closely linked.  The more of these match activities performed, the greater the level of soreness and reduction in performance.

What can the US players now expect?  They will experience some degree of soreness - beginning on Friday, peaking on Saturday and beginning to subside by Sunday or Monday.  Also speed and power will be impacted on Friday but should recover by the beginning of the next week.  Add to that, treatment of injuries sustained during the match.  The key task for the team coaches and training staff will be to manage recovery.  Construct training sessions, provide the proper diet and hydration strategy and rehab therapies to speed the recovery process so that players are ready to face Belgium on Tuesday. 

This study has several implications for the US team as well as teams playing at other levels.  First, complete recovery from a competitive soccer match is a slow process, even for well-trained professional players.  These results indicate that it may take more than three days (72 hours) to fully recover.  The US-Ghana match was played on Sunday followed by the Germany match on Thursday.  That’s a four-day recovery period (in contrast, Germany had an extra day).  It is quite possible that the US team was not fully recovered.  It is also likely that training during the recovery days was less than optimal due to soreness and diminished performance.  The FIFA data on distance covered indicates that most US players covered as much if not more distance in the Germany match as in the previous two.  However, FIFA does not provide data on match activities such as changes in directions and short sprints.  Is it possible that the US players were a bit slower in their reactions to the game and their ability to stop, start and change directions?

As for other teams playing at other levels, short recovery periods can impact match performance.  For example, women’s collegiate soccer often uses a Thursday-Sunday or Friday-Sunday playing schedule.  This means that teams are competing with only 48 or 72 hours of recovery.  Youth teams often compete with less than 24 hours between matches.  Based on the results of this study, it is quite likely that performance of these teams will be less than maximal.  It is very likely that soreness and the loss of strength, speed and power will impact the match.  In addition, playing matches in a fatigued state can place players at risk of injury.  Earlier research has shown that fatigue is a key contributor to muscle strains as well as joint injuries such as ACL tears.
  
Second, the loss of hamstring strength due to fatigue has implications for injury.  The researchers found that strength of the dominant leg was impacted more than that of the non-dominant leg.  This is probably due to more technical actions such as shots and long passes performed with the dominant leg.  It may also explain why hamstring strains occur more often to the dominant leg - greater use, more fatigue, greater injury risk.  Coaches should also be aware during the 72 hours post-match,  having players perform maximal sprints as part of their training session could raise the risk of hamstring injury.

Third, coaches should consider fitness training that includes changes in direction and short sprints.  These are often encountered during activities such as small-sided games and can be included in other soccer-specific drills.  Perhaps by training for these match specific activities, teams can limit the toll matches take on strength, speed and power.

Unfortunately, it will take the US team a few days to fully recover from the Germany match.  However, the good news is that there is a need to recovery.  The team has survived the group of death and is looking forward to the knockout stage!

Reference:

Nedelec M, McCall A, Carling C, Legall F, Berthoin S, Dupont G. (2014) The influence of soccer playing actions on the recovery kinetics after a soccer match. Journal of Strength and Conditioning Research, 28: 1517-1523.