Research Review by Dr. Shawn Thistle©

Date:

2004

Study Title:

Hamstring injury occurrence in elite soccer players after pre-season strength training with eccentric overload

Authors:

Askling C, Karlsson J, Thorstensson A

Publication Information:

Scandanavian Journal of Medicine & Science in Sports 2003; 13: 244-250

Summary:

Hamstring injuries are common in sports, particularly in sports that demand high output of power and speed, such as soccer. Muscle strength deficiency has been proposed as the main risk factor for hamstring injuries. Strength training has been recommended as a preventive measure in order to avoid hamstring muscle injuries, despite the lack of conclusive human research (most of this work is based on animal muscle).

Recently, increasing amounts of evidence have pointed toward the benefits of incorporating eccentric muscle actions (i.e. lengthening a muscle under load) into training regimens. This makes sense particularly for the hamstring muscle group as many of its actions are performed in an eccentric manner.

This study aimed to evaluate the effect of incorporating eccentric muscle actions into the pre-season training programs of elite Swedish soccer players. Thirty male subjects from two of the top teams in the Swedish premiere league were randomly assigned to either a training group or control group. The training group underwent 16 sessions of specific hamstring training (every 5th day for the first 4 weeks and then every 4th day for the remaining 6 weeks), done in a non-fatigued state, after a standardized warm-up. The athletes were familiarized with the exercise protocol before the study began.

The training consisted of both concentric and eccentric hamstring actions performed lying prone on a fly-wheel ergometer. The control group still performed their regular pre-season program without the specific hamstring exercises. Outcome measures used in this study were isokinetic muscle strength, running speed, range of motion and injury reporting during the season.

The training group showed a significant increase in both concentric and eccentric hamstring muscle strength after the training period, whereas no differences were observed in the control group. The training group also improved their running times (30 m maximal sprint) more than the control group.

Most importantly, during the 10-month study period, a significantly lower number of injuries occurred in the eccentric training group (3/15 players) versus the control group (10/15 players - although 7 of those ten injuries were classified as minor).

Conclusions & Practical Application:

The main finding of this study is that hamstring injuries seem to be reduced by the incorporation of eccentric training into a pre-season program. Eccentric training also increased strength of the hamstrings more than normal training.

One other interesting trend was that players who had previously suffered a hamstring injury were more likely to suffer a repeat injury. This has implications for trainers and strength coaches, as they should be aware of their athletes' previous injury history.

Although this is a small study, done with a select group of athletes, it lays a solid foundation for future work in this area. Larger scale studies with athletes from various sports would be the next step in this line of research.