Females competing in sports such as football (soccer), baseball, softball and basketball are at higher risk of concussion than their male counterparts. It is unclear what are the main contributory factors to this increased potential for injury but it has been suggested that females are unable to stabilise the head-neck segment as well as males. US researchers carried out a biomechanical study into subjects’ ability to control the head-neck segment when an external force was applied to it (‘Gender difference in head-neck segment dynamic stabilisation during head acceleration’, Medicine and Science in Sports and Exercise 2005; 37(2):272-279).
Twenty male and 20 female subjects took part in the study. The participants’ height, weight, head-neck segment length and neck girth were assessed. The gender-specific mass of the head-neck segment was calculated as a percentage of total body mass (male = 8.26% and female = 8.20%). The researchers collected data on:
* head-neck flexion and extension peak angular displacements and accelerations
* role of sternocleidomastoid (SCM) and upper trapezius muscles in controlling head-neck flexion and extension
* head-neck segment stiffness
* isometric flexor and extensor strength.
Subjects warmed up using a standardised neck warm-up and stretch routine. They were then seated in the ‘external force applicator’, a pulley system connected to the head that enabled a 1kg mass to be dropped from a predetermined height of 15cm, creating a load of approx 11lb (50N)!
The female subjects exhibited significantly greater head-neck segment peak angular acceleration (50%) and displacement (39%) than males, despite initiating muscle activity significantly earlier (SCM only) and using a greater percentage of their maximum head-neck segment muscle activity. To you and me that means the women’s heads and necks accelerated faster and moved more, despite earlier recruitment and greater muscle activity than the men; which is bad news if you want to avoid becoming concussed from a knock on the head.
The researchers found several predisposing factors to increased risk of concussion among females compared to males:
* poor isometric strength (49% of the strength of male subjects on average)
* small necks (neck girth was on average 30% less)
* smaller heads (on average 43% of male mass) * inability to resist force: head-neck segment stiffness was on average 29% less.
The team concluded that females may be at higher risk of concussion from sports with greater loads being applied to the head, such as football, martial arts or rugby.
Strengthen against pain
Neck pain is one of the most common problems encountered in primary health care and weak neck muscles have been thought to be associated with chronic neck pain. A Finnish research team recently investigated the effect of high and low intensity neck muscle training and their effects on pain (‘Effects of neck muscle training in women with chronic neck pain: One-year follow-up study’, Journal of Strength and Conditioning2006; 20(1):6-13). One hundred and eighty females with chronic neck pain took part in the study and were split into three groups:
* high intensity, isometric exercises (STG)
* local muscle endurance, dynamic exercises (ETG)
* control (CG).
Both methods of training increased neck and muscle strength in the first two months of the trial and the results were maintained and even further improved during the course of the 12-month monitoring period. The research team concluded that increased neck strength was associated with reduced neck pain.
Heading for brain damage?
Whether you know it as football or soccer, the beautiful game remains one of the most popular sports in the world. During the last 20 to 30 years, the game has increased in popularity among women, who now account for 22% of soccer players throughout the world. Recent studies have shown that female players have an increased risk of injury while playing football. Concussions account for 11% of all game injuries in the women’s game, compared to 9% in men’s football. During recent years it has been suggested that even simple heading of the ball is dangerous to the brain. While evidence continues to grow in the men’s game, there has been a lack of research into this aspect of the women’s game.
Step forward the Swedish research team from the University of Umeå (‘Serum concentrations of two biochemical markers of brain tissue damage S-100B and neurone specific enolase are increased in elite female soccer players after a competitive game’, British Journal of Sports Medicine2006; 40:313-316). The team decided to look at markers of brain damage during competitive matches and recruited 44 players from four elite female football teams in the Swedish Elite Football League. Venous blood samples were taken before and immediately after a competitive match. The clotted blood was centrifuged, frozen and stored at -78˚C before serum concentrations of S-100B and neurone specific enolase (NSE) were analysed. Independent analysts recorded the number of contacts made by each subject during all the matches, classified as:
* headers with jumps/collisions/falls
* headers without jumps/collisions/falls
*jumps, collisions and falls without head contact.
The average number of headers during a match was 3.1. The study showed that serum concentrations of both S-100B and NSE were increased. The changes in S-100B concentration after the game were significantly correlated with both the number of headers and the number of other trauma events occurring during the match. These findings support the results of a parallel study of male football players. The researchers concluded that elite female football players resemble male players when comparing the increases in brain tissue damage arising from heading and other trauma events.