Earl R. Cooper

The influence of ankle support on postural control

Postural control assessments are commonly administered to athletes as part of a pre-season screening. Establishing a baseline level of function permits the clinician to compare post-injury results to normal functioning during the return to play decision-making process. In the athletic setting, follow-up tests may be completed on the sideline immediately following injury. We sought to examine the effect of commonly administered external ankle joint support on postural control using the balance error scoring system (BESS) and the NeuroCom sensory organization test (SOT). Nineteen volunteers free from balance issues completed three sessions with varied ankle support: bilateral prophylactic ankle taping, laced bracing device, or barefoot. Each session included an initial balance assessment on the BESS and SOT, a 20 min treadmill walk, and post-walk balance test. Fewer errors, indicating improved balance, were committed on the BESS during the barefoot condition than the braced ankle condition (p=0.044) at the pre-walk assessment. During the post-walk assessment, fewer errors were committed during the barefoot condition compared to the braced ankle condition (p=0.034) and the taped ankle condition (p=0.037). All ankle support conditions showed similar improvements in balance between the pre and post-walk assessments on the BESS (p<0.001) and SOT composite balance score (p=0.009). These findings indicate that ankle support devices may influence postural control on the BESS, but not on the NeuroCom SOT. Clinicians using the BESS as a balance assessment device at multiple time points should be consistent in the application of ankle support devices.

Exertional heat illness in American football players: when is the risk greatest?

CONTEXT Knowledge about the specific environmental and practice risks to participants in American intercollegiate football during preseason practices is limited. Identifying risks may mitigate occurrences of exertional heat illness (EHI). OBJECTIVE To evaluate the associations among preseason practice day, session number, and wet bulb globe temperature (WBGT) and the incidence of EHI. DESIGN Descriptive epidemiology study. SETTING Sixty colleges and universities representing 5 geographic regions of the United States. PATIENTS OR OTHER PARTICIPANTS National Collegiate Athletic Association football players. MAIN OUTCOME MEASURE(S) Data related to preseason practice day, session number, and WBGT. We measured WBGT every 15 minutes during the practice sessions and used the mean WBGT from each session in the analysis. We recorded the incidence of EHIs and calculated the athlete-exposures (AEs). RESULTS A total of 553 EHI cases and 365 810 AEs were reported for an overall EHI rate of 1.52/1000 AEs (95% confidence interval [CI] = 1.42, 1.68). Approximately 74% (n = 407) of the reported EHI cases were exertional heat cramps (incidence rate = 1.14/1000 AEs; 95% CI = 1.03, 1.25), and about 26% (n = 146) were a combination of exertional heat syncope and heat exhaustion (incidence rate = 0.40/1000 AEs; 95% CI = 0.35, 0.48). The highest rate of EHI occurred during the first 14 days of the preseason period, and the greatest risk was during the first 7 days. The risk of EHI increased substantially when the WBGT was 82.0°F (27.8°C) or greater. CONCLUSIONS We found an increased rate of EHI during the first 14 days of practice, especially during the first 7 days. When the WBGT was greater than 82.0°F (27.8°C), the rate of EHI increased. Sports medicine personnel should take all necessary preventive measures to reduce the EHI risk during the first 14 days of practice and when the environmental conditions are greater than 82.0°F (27.8°C) WBGT.

American football and fatal exertional heat stroke: a case study of Korey Stringer

On August 1, 2001, Korey Stringer, a Pro Bowl offensive tackle for the Minnesota Vikings, became the first and to date the only professional American football player to die from exertional heat stroke (EHS). The death helped raise awareness of the dangers of exertional heat illnesses in athletes and prompted the development of heat safety policies at the professional, collegiate, and interscholastic levels. Despite the public awareness of this death, no published study has examined in detail the circumstances surrounding Stringer’s fatal EHS. Using the well-documented details of the case, our study shows that Stringer’s fatal EHS was the result of a combination of physiological limitations, organizational and treatment failings, and extreme environmental conditions. The COMfort FormulA (COMFA) energy budget model was used to assess the relative importance of several extrinsic factors on Stringer’s EHS, including weather conditions, clothing insulation, and activity levels. We found that Stringer’s high-intensity training in relation to the oppressive environmental conditions was the most prominent factor in producing dangerous, uncompensable heat stress conditions and that the full football uniform played a smaller role in influencing Stringer’s energy budget. The extreme energy budget levels that led to the fatal EHS would have been avoided according to our modeling through a combination of reduced intensity and lower clothing insulation. Finally, a long delay in providing medical treatment made the EHS fatal. These results highlight the importance of modern heat safety guidelines that provide controls on extrinsic factors, such as the adjustment of duration and intensity of training along with protective equipment modifications based on environmental conditions and the presence of an emergency action plan focused on rapid recognition and immediate on-site aggressive cooling of EHS cases.

An Evaluation of Portable Wet Bulb Globe Temperature Monitor Accuracy

CONTEXT   Wet bulb globe temperature (WBGT) is the gold standard for assessing environmental heat stress during physical activity. Many manufacturers of commercially available instruments fail to report WBGT accuracy. OBJECTIVE   To determine the accuracy of several commercially available WBGT monitors compared with a standardized reference device. DESIGN   Observational study. SETTING   Field test. PATIENTS OR OTHER PARTICIPANTS   Six commercially available WBGT devices. MAIN OUTCOME MEASURE(S)   Data were recorded for 3 sessions (1 in the morning and 2 in the afternoon) at 2-minute intervals for at least 2 hours. Mean absolute error (MAE), root mean square error (RMSE), mean bias error (MBE), and the Pearson correlation coefficient ( r) were calculated to determine instrument performance compared with the reference unit. RESULTS   The QUESTemp° 34 (MAE = 0.24°C, RMSE = 0.44°C, MBE = -0.64%) and Extech HT30 Heat Stress Wet Bulb Globe Temperature Meter (Extech; MAE = 0.61°C, RMSE = 0.79°C, MBE = 0.44%) demonstrated the least error in relation to the reference standard, whereas the General WBGT8778 Heat Index Checker (General; MAE = 1.18°C, RMSE = 1.34°C, MBE = 4.25%) performed the poorest. The QUESTemp° 34 and Kestrel 4400 Heat Stress Tracker units provided conservative measurements that slightly overestimated the WBGT provided by the reference unit. Finally, instruments using the psychrometric wet bulb temperature (General, REED Heat Index WBGT Meter, and WBGT-103 Heat Stroke Checker) tended to underestimate the WBGT, and the resulting values more frequently fell into WBGT-based activity categories with fewer restrictions as defined by the American College of Sports Medicine. CONCLUSIONS   The QUESTemp° 34, followed by the Extech, had the smallest error compared with the reference unit. Moreover, the QUESTemp° 34, Extech, and Kestrel units appeared to offer conservative yet accurate assessments of the WBGT, potentially minimizing the risk of allowing physical activity to continue in stressful heat environments. Instruments using the psychrometric wet bulb temperature tended to underestimate WBGT under low wind-speed conditions. Accurate WBGT interpretations are important to enable clinicians to guide activities in hot and humid weather conditions.

Environmental Condition and Monitoring

The ambient environment (i.e., weather conditions) can significantly impact one’s ability to thermoregulate, particularly when exercising in environmentally stressful conditions where an imbalance between metabolic heat production and heat dissipation from the body is not adequately regulated. Empirical, direct, and rational heat indices have been developed by scientists to gauge the degree of heat strain one may experience in a range of thermal conditions. These measures are applied in athletic, military, and occupational settings to provide guidance on physical activity and/or clothing modifications that mitigate the risk of experiencing exertional heat illness. This chapter will provide an overview of common heat indices in physical activity settings and highlight the benefits and drawbacks of each index in practical applications. Lastly, the chapter will provide a case example from the Georgia High School Association in developing a set of weather-based activity modification guidelines based on an empirical study of football players’ heat injuries.

Work-to-Rest Ratio

Multiple organizations created work-to-rest ratio (WRR) guidelines to maintain safety and prevent exertional heat illnesses (EHIs) during physical activity in hot ambient conditions. Athletes, military personnel, and occupational workers should choose appropriate WRRs based on current ambient conditions and exercise intensity. The goal of WRRs is to mitigate rise in core temperature during exercise by keeping exercise duration short, while increasing the frequency and duration of rest breaks to enhance heat dissipation. When implemented correctly, performance improvements should be seen while avoiding heat illnesses.