Inter sex muscle activation differences

A study recently published in the journal of "Bone and Joint" has aimed to find the differences between males and females in their performance of football kicks, and relate that to the difference in ACL injury rates.

There is existing research which shows that females are more likely to suffer non-contact ACL injuries than males, however no direct cause for this has been established.

The study was carried out at Washington University School of Medicine, and was lead by Dr H Brophy, a former professional footballer.

The study involved 13 male and 12 female college football players. These athletes performed 5 in-step kicks, and 5 side foot kicks each, with their movements being recorded using 10 video cameras, 21 retroflective markers and 16 electrodes. The activation of 7 muscles (iliacus, gluteus maximus, gluteus medius, vastus lateralis, vastus medialis, hamstrings and gastrocnemius) were recorded in both legs, and the activation of 2 muscles (hip adductors and tibialis anterior) were recorded in the kicking leg. Muscle activation was measured as a percentage of maximum voluntary isometric contraction.


The Results

• In the kicking leg, males generated about 4 times as much hip flexor activation as females (123% in males compared to 34% in females).
• In the supporting leg, males generated more than twice as much gluteus medius activation (124% in males compared with 55% in females) and vasteus medialis activation (139% in males compared with 69% in females).
• An interesting observation made during the analysis was that, due to females having less activation of the hip adductors, their hips tend to "collapse" into adduction during the kicking motion, increasing the risk of injury.

Although Brophy states that this study doesn't establish a direct cause and effect relationship between muscle activation, knee alignment and ACL injuries, he did conclude by saying, "Activation of the hip adductors may help protect players against ACL injuries."

There are a number of positive and negative points to consider with this study. The main criticism i have of this study is the lack of information we are given concerning the way in which each kick was carried out (ie. was it carried out with maximal effort to replicate a shot, or an effort level to replicate a pass?). I also feel that the amount of information given concerning the athletes participating in the test is too vague. More knowledge of experience and skill level could affect the way these results are viewed.

There are positives as well though. The size of the study group (13+12) is impressive for a study working in such detail, which suggests reliability in the results. The study was also carried out at a reputable university, which lends to it's credibility.

Overall, i feel that this is a very interesting and important study. Although the results don't confirm a cause and effect relationship, i'm sure this study will act as a stepping-stone to more specific research being carried out in the future. In the mean time, i feel that Dr Brophy's suggesting to place a higher focus on strengthening muscles surrounding the hip should be taken very seriously, especially by females.



Ben Brown

Sports drinks explained

Sports drinks first appeared about 50 years ago, when American college teams began to experiment with them. These colleges found that combining salt, sugar and water aided athletic performance. Athletes experienced a slowing in the rate of dehydration, as well as energy sources being replenished. This allowed athletes to work harder, work for longer and think more clearly.

Today the choice of sports drinks is huge. The basic formula is still there though, with water, carbohydrates and electrolytes making the base. The developments made in sport science have made it possible to calculate what amount of each basic ingredient will be most beneficial to an athlete. It is proven that carbohydrate content must be between 5-8% to be effective, any less than this and it won't be enough to have an effect on performance, any more than this and the body's absorption of water will be impaired.

There is a common misconception that all sports drinks are the same. However, sports drinks can actually be put into three different categories. Each one is designed to suit a different occasion.

Isotonic drinks contain a balance of carbohydrates, electrolytes and water which is the same as in the human body. This can be absorbed at roughly the same speed as water, but has greater calorific value.

Hypotonic drinks have a carbohydrate and electrolyte to water ratio lower than that of the body's. This allows the fluid to be absorbed more quickly, but with less energy replenishment, making this drink suitable for sports where dehydration is likely.

Hypertonic drinks have a greater carbohydrate and electrolyte to water ratio than in the body, meaning the fluid is absorbed the slowest, but the energy replenishment is greatest. This form of drink is most effective when used as a post-exercise recovery drink.

Lucozade, Gatorade and Powerade all come under the category of Hypertonic drinks. It is therefore important to consider what your sport demands before choosing which sports drink to use, as well as which time you are consuming it (pre, during or post sport).



Ben Brown