Balance and injury in elite Australian footballers.

This project measured pre-season balance ability and determined its relationship to knee and ankle ligament injuries during the season for professional Australian footballers. The balance test involved the players stepping onto a foam balance mat on top of a force plate and maintaining single limb balance. Throughout the playing season, injuries were monitored. The results from two hundred and ten players participating in this project were analysed. During the 2003 season, 8 % (17 out of 210) sustained a knee ligament injury and 10 % (21 out of 210) sustained an ankle ligament injury. Multivariate analysis revealed that pre-season balance ability was a significant independent predictor of ankle ligament injury. Players with low balance ability had at least twice as many ankle ligaments injuries as those with average or good balance ability. Balance ability was not a significant predictor of knee ligament injuries. The height of the players was the only significant independent predictor of knee ligament injuries. Low pre-season balance ability was associated with an increased risk of ankle ligament injury. A modifiable injury risk factor has been identified. Research is now required to determine the optimal training regime to enhance balance ability and whether this translates to a reduction in the incidence of ankle injuries.

Relationship between static and dynamic balance tests among elite Australian Footballers.

Research assessing the direct relationship between static and dynamic balance ability of athletes is sparse. The aim of this project was to determine the relationship between a static balance task on a firm surface with a stepping balance task on an unstable surface. Thirty-seven Australian male professional footballers participated in the study. The static test involved maintaining single limb stance on a force platform. The other balance test involved stepping on to a balance mat on top of the force platform and maintaining single limb stance. The centre of pressure was monitored and the maximum excursion in the medial-lateral direction was recorded and used as the balance value. It was found that the magnitude of the maximum centre of pressure excursion was significantly greater (53%) for the stepping balance task. There were significant but low correlations for the centre of pressure excursion values between the two balance tests for the right limb and average of both limbs. There was no significant correlation between the test values for the left limb. Only a small proportion of the variance could be explained by each test: 16% for right limb values, 7% for left limb values and 11% for the average of both limbs. Given the overall weak associations between the two balance test values, it was concluded that performance in the static balance test was not reflective of performance in the dynamic balance test. Attempting to infer dynamic balance ability based on static balance ability should be avoided.

Does a balance deficit persist in Australian Football players with previous lower limb ligament injury?

A history of lower limb ligament injury is a commonly-cited risk factor for another similar injury. During the acute phase of injury, there is a balancing skill deficit in the injured limb. It has been unclear as to whether this deficit persists in the medium-to-long term for previously injured Australian footballers, contributing to the risk of re-injury. This study compared the balance ability of footballers with and without previous lower limb ligament injury and, for previously injured players, the balance ability of the previously injured limb to the opposite uninjured limb. A total of 216 players from 6 teams from the Australian Football League were tested. The balance task comprised stepping on to a foam mat on top of a force plate and maintaining one-legged balance. The subjects were divided into 4 groups based on their injury history: all ankle injuries to only one limb, recent ankle injuries to only one limb (within the last 12 months), knee ligament injury only to one limb, and no previous ankle or knee ligament injury. Statistical analysis revealed that there was no significant difference between the balance scores of any of the previously injured players and those with no previous lower limb ligament injury. There was no significant difference between the balance score of the previously injured limb with the opposite uninjured limb. It appears that a balance deficit does not persist in Australian Football players with previous lower limb ligament injury.

Impact energy attentuation of protective football headgear against a yielding surface.

There is no standard test to assess the ability of soft headgear to prevent the likelihood of head injuries in the Australian football codes. Therefore the impact energy attenuation of protective football headgear was assessed using a yielding artificial headform and impact surface to characterise the impact scenario. Seven soft football headgear of varying mass, materials and thickness were dropped from a height to generate impact energy of 56 J. The headgear were tested for a number of different impact locations. Accelerometers within the headform monitored the impact mechanics. A Head Injury Criterion (HIC) of 1000 was selected as the injury threshold. Reliability data, collected one week apart, revealed that the results were highly reproducible. Although several of the headgear generated HIC values about 1000 for the various impact locations, only one of the headgear, that with the greatest thickness (15 mm) generated a HIC score below 1000 for impacts to the side and front of the headgear. There was a significant correlation between headgear thickness and HIC scores. It was concluded that all but one of the commercially available soft football headgear tested provided inadequate impact energy attenuation due to the limited amount of padding. It is postulated that the padding material of the headgear would need to be at least 15 mm thick to offer adequate protection.

Effect of heavy dynamic resistive exercise on acute upper-body power.

There is limited research to support the notion that heavy resistive exercise immediately before a power movement may acutely enhance performance. Upper-body acute power enhancement during a stretch-shorten cycle (SSC) movement has not been previously investigated. The aim of this project was to determine whether a set of 5 repetitions of 5 repetition maximum (RM) bench press preceding explosive push-ups would significantly influence indicators of power: impulse and maximum rate of force development. Subjects randomly performed either explosive push-ups only over a force platform or a set of 5RM bench press before the explosive push-ups. There were no significant differences for any of the force platform data when the explosive push-ups were preceded by a set of 5RM bench press. It appears that heavy dynamic resistive upper-body exercise on its own before an upper-body power activity is inadequate in augmenting short-term power.

Isokinetic strength related to jumping but not kicking performance of Australian footballers.

The relationships between lower limb strength and two Australian football (AF) skills were assessed for 19 sub-elite AF players. Knee extension (KE) and knee flexion (KF) strength were assessed using a Biodex isokinetic dynamometer at angular velocities of 60, 240 and 360 degrees/sec. The two AF skills evaluated were running vertical jump (VJ) and kicking performance (KP). VJ performance was defined as the maximal jump height measured with a Yardstick device. KP was gauged through video analysis, as the post-contact resultant ball velocity (BV) during maximal effort drop punt kicking. Strength was measured as the isokinetic peak torque (PT value. No significant correlations were detected between the isokinetic knee strength values and maximal kicking velocity. Low to moderate significant correlations (r = 0.55 - 0.69, p < 0.05) were detected between the isokinetic measures and VJ height. It may be inferred that additional strengthening of the knee musculature may enhance running VJ performance, but not necessarily kicking velocity for this group of sub-elite AF players.

A review of resistance exercise and posture realignment.

Exercise has been promoted in an attempt to correct postural deviations, such as excessive lumbar lordosis, scoliosis, kyphosis, and abducted scapulae. One of the assumed causes of these conditions is a weak and lengthened agonist muscle group combined with a strong and tight antagonist muscle group. Strengthening and stretching exercises have been prescribed accordingly. It is implied that strengthening exercises will encourage adaptive shortening of the muscle-tendon length, reposition skeletal segments, and produce static posture realignment. A review of the literature has found a lack of reliable, valid data collected in controlled settings to support the contention that exercise will correct existing postural deviations. Likewise, objective data to indicate that exercise will lead to postural deviations are lacking. It is likely that exercise programs are of insufficient duration and frequency to induce adaptive changes in muscle-tendon length. Additionally, any adaptations from restricted range-of-movement exercise would likely be offset by daily living activities that frequently require the body segments to go through full ranges of motion.

Sports injury surveillance and protective equipment.

Protective equipment is adopted in the hope of reducing the incidence and severity of injuries. To objectively assess the effectiveness of such equipment, injury data is required prior to and after the introduction of this countermeasure. In many cases, there has been no appropriate evaluation of the countermeasure. Pre- and postintervention data is vital to the protective equipment developer. Such information may be obtained from injury surveillance systems. Other information which is just as vital but not obtainable from such a system is injury tolerance levels. Additional information from injury surveillance such as the type of protective equipment worn, its condition prior to and after impact, and a description of the event leading to injury would be most valuable.