Ankle sprains are a common athletic injury. Previous ankle sprains and a high body mass index (BMI) have been identified as risk factors for non-contact inversion ankle sprains (NCIAS) in football players, regardless of position. Commonly, ankle braces or tape are used in an attempt to reduce the risk of sprain, but the effectiveness of these strategies has recently been called into question. However, there is increasing support for the use of single limb balance training (SLBT) to reduce ankle injury risk.
The authors of this study hypothesized that having previous ankle injury and a high BMI increase NCIAS risk due to impaired ankle stability, and a lack of control of upper body mass during the dynamic movements required in football. As such, SLBT could counteract these deficits and lower risk. Therefore, this study aimed to determine if SLBT on a foam stability pad can reduce NCIAS incidence in high school football players who were at increased risk.
During the intervention period, 125 different players from 2 high school football teams were observed over 3 seasons. A previous history of ankle sprains, height, body mass, and use of ankle braces or tape were noted. 175 player seasons were followed in total. Players were assigned risk levels (minimal, low, moderate, or high) for NCIAS based on their BMI and previous ankle injury history. Players in the low, moderate, or high risk categories were assigned to perform the stability pad intervention.
Subjects in the intervention group performed SLBT on a foam stability pad for 5 minutes per leg (both legs were trained), five times per week for 4 weeks in the preseason. Subjects completed the same type of training twice weekly for nine weeks during football season. The SLBT was incorporated into the subjects' regular weight room routines as part of a balance training station. Compliance was monitored by the team Athletic Therapist, and subjects had to make up for missed sessions.
The main outcome measure was incidence of NCIAS, which was defined as a sprain that required the player to miss at least one game or practice, and it had to be non-contact (ie did not occur while tackling or blocking, etc). The team Athletic Therapist collected data on NCIAS injuries and the number of missed games and practices due to such an injury. Injury incidence was calculated in units of per 1000 player exposures (an exposure being participation in a game or practice, and the analysis included the use of 95% confidence intervals). Statistical analysis included chi square and Fisher exact tests to compare NCIAS incidence before and after the introduction of the intervention. 107 player seasons (for 84 players) were followed prior to the introduction of the intervention as a comparison.
Pertinent results of this study include:
• 128 out of the 175 players seasons were classified as low, moderate, or high risk and were thus assigned to the intervention analysis
• 12 players were non-compliant, the rest of the players completed at least 34 out of 38 training sessions (20 preseason and 18 in-season)
• pre-intervention period: the prevalence of NCIAS was 3% in the minimal risk group and 18% in the low-moderate-high risk group; 21 of the 84 players sustained an inversion ankle sprain, 13 of which were NCIAS; nine of those were by players with a previous history of ankle sprain
• post-intervention period: the prevalence of NCIAS was 7% prevalence in the minimal risk group and 5% prevalence in the low-moderate-high risk group (actually 4% as one of the players in this group did not complete the intervention / was non-compliant); 20 out of 125 players had inversion ankle injuries, 9 of which were NCIAS and five of those were by players with a previous history of ankle sprain
• overall, the prevalence of NCIAS was significantly reduced for those at risk – a 77% reduction in injury incidence for those in similar risk groups (2.2 / 1000 exposures to 0.5 / 1000 in the groups when combined).