Baseline Aerobic Fitness in High School and College Football Players: Critical for Prescribing Safe Exercise Regimens.

Background: Nontraumatic fatalities occur on a regular basis in high school (HS) and college football athletes, primarily in obese linemen performing high-intensity exercise. One contributing factor to these deaths may be a mismatch between baseline aerobic (cardiorespiratory) fitness and exercise regimens.

Hypothesis: There is a wide range of aerobic fitness in HS and college football players. Body mass index (BMI) is a safe and simple method for estimating baseline aerobic fitness.

Study Design: Retrospective cohort study.

Level Of Evidence: Level 3.

Methods: A retrospective review was performed on 79 HS football athletes who had VO (mL·kg·min) measured during the offseason. Multivariate regression analysis was used to determine if BMI (obese, overweight, and normal; kg/m), position played (linemen vs other), year in school (freshmen vs other), and/or race (African American vs White) were risk factors for poor aerobic fitness. A separate cohort of 135 (48 HS; 87 college) football athletes performed a 6-minute run test to determine speed (miles/min), extrapolate VO, and calculate reference values for suggested upper threshold safe starting speeds (85% of maximum) for aerobic training based on BMI. The relationship between BMI and VO was assessed. The exercise regimens (speeds) of 2 collegiate football fatalities from the public domain were used to predict their VO values.

Results: Mean VO (mL·kg·min) was 38.5 ± 8.6 (range 19.1-60.6); when grouped by BMI, low scores (<40) were found in 87.5% of obese (32.4 ± 7.7), 47.8% of overweight (40.8 ± 7.6), and 45.2% of normal (41.4 ± 7.8) athletes. VO was significantly lower in linemen (32.8 ± 6.4; = 0.007) compared with nonlineman (41.8 ± 7.9), and in obese players (by BMI; 32.4; = 0.019) compared with nonobese players (41.4 ± 7.6), but did not differ by age, year in school, or race. Means for speed (min/mile) and extrapolated VO (mL·kg·min) for the 6-minute run test by BMI groups were both significantly different ( = 0.001) for normal (7.0 ± 0.6; 51.1 ± 2.6), overweight (7.6 ± 0.8; 46.5 ± 3.2), and obese (8.9 ± 1.5; 36.8 ± 5.9) athletes. There was a significant negative correlation ( = -0.551; = 0.001; = 0.304) between VO and BMI. Safe starting speed recommendations for running 1 mile range from 7.3 to 12.1 min/mile for BMIs 20 to 40 kg/m for HS and college athletes. For the 2 fatalities (mean, BMI of 36.5 kg/m) repetitive sprint speeds were 49 and 89% higher than our safe starting speeds for their BMI.

Conclusion: A large spectrum of baseline aerobic fitness was noted in HS and college football players. Obese players and linemen had statistically lower baseline aerobic fitness, a major risk factor for possible heat illness. BMI is an acceptable surrogate for VO and can be employed to develop safe training regimens without the need for a maximum fitness test, which can place the athlete at risk for a medical event.

Clinical Relevance: Knowledge of BMI provides an estimate of baseline aerobic fitness and a foundation for prescribing safe, individualized exercise regimens.