Responses and adaptations to acute and chronic high-intensity interval training
Gist, Nicholas H.
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Sprint interval training (SIT) involving repeated 30-s “all out” efforts appears to be an effective and time-efficient stimulus for fitness improvement. Three studies were completed for this dissertation. The purposes were: 1) to perform a meta-analysis to assess the population effect of SIT on aerobic capacity; 2) to compare physiological responses of two SIT protocols of different modality; and 3) to determine the effects of a SIT intervention on fitness and performance. The meta-analysis revealed SIT has a small-to-moderate effect (Cohen’s d = 0.32, 95% CI: 0.10, 0.55; z = 2.79, p < 0.01) on aerobic capacity. The effect is large in comparison to no-exercise control groups (Cohen’s d = 0.69, 95% CI: 0.46, 0.93; z = 5.84; p < 0.01) and not different when compared to endurance training control groups (Cohen’s d = 0.04, 95% CI: -0.17, 0.24; z = 0.36, p = 0.72). In the second study, mean values for %VO2peak and %HRpeak for cycling (80.4 ± 5.3% and 86.8 ± 3.9%) and calisthenics (77.6 ± 6.9% and 84.6 ± 5.3%) were similar (p > 0.05), but calculated effect sizes revealed a meaningful difference in %VO2peak (Cohen’s d = 0.51) and %HRpeak (Cohen’s d = 0.57). In the third study, moderately-trained members of the Army Reserve Officers’ Training Corps (ROTC) completed 4 weeks of exercise training 3 days∙wk-1 consisting of either ~60 min of typical cadet physical training (TCT) or whole-body calisthenics (HIT) involving 4-7 sets of 30-s “all out” burpees separated by 4 min of active recovery. Following training, there were no changes in VO2peak, anaerobic capacity or Army Physical Fitness Test (APFT) performance (p > 0.05). For the TCT group, mitochondrial function (Tc: time constant of recovery) was improved (2.4 ± 4.6 s decrease in Tc; p = 0.081; d = -0.51 (-2.37, 1.35)); whereas, mitochondrial function decreased in HIT (2.4 ± 4.6 s increase in Tc; p = 0.087; d = 0.50 (-1.36, 2.36)). In conclusion, studies in the literature indicate that SIT has a large effect on aerobic capacity relative to no exercise and an effect similar to prolonged, moderate-intensity continuous exercise. SIT involving whole-body calisthenic exercise elicits vigorous cardiovascular responses with peak values less than cycling SIT. SIT involving low-volume whole-body calisthenics sustains fitness in Army ROTC cadets. A program that includes SIT as part of a larger program may be well suited to moderately-trained armed forces personnel seeking to maintain fitness with minimal time commitment and without access to equipment.