The Effect of High Intensity Interval Run Training on Cross-sectional Area of the Vastus Lateralis in Untrained...

Aerobic cycling has been repeatedly shown to induce hypertrophy in skeletal muscle across a variety of populations, while there has been a lack of investigation into the impact of running upon hypertrophy. An increasingly popular model of aerobic exercise is high-intensity interval training (HIIT); in addition to its positive impact upon cardiovascular health, HIIT may be sufficient for inducing significant muscular hypertrophy. Therefore, the purpose of this investigation was to examine the influence of a high-intensity interval running protocol upon hypertrophy of the vastus lateralis in an untrained, young population. Twelve recreationally active university students (Male: 2; Female: 10; 19.9±0.5 yr.; 169.8±1.9 cm; 63.8±2.3 kg; VO_2max: 42.1±1.6 ml•kg^-1min^-1) completed 24.5±0.6 sessions of high-intensity interval run training over 10 weeks. The protocol consisted of four sets of 4 minutes running at 90-95% HR_max followed by 3 minutes active rest at 70% HR_max. Relative and absolute aerobic capacity increased 5.2±2.2% and 6.0±2.3% respectively as a result of the intervention (p< 0.05). Cross-sectional area (CSA) of the vastus lateralis was measured via panoramic ultrasound imaging pre- and post-intervention. Following the protocol, CSA of the intervention group was 10.6±2.7% greater (p< 0.05), while that of the control group did not change. This is the first data to demonstrate hypertrophy of the vastus lateralis in a young population following a running protocol. These data support the existing body of evidence suggesting aerobic exercise to be an effective mode of improving cardiorespiratory fitness as well as increasing whole muscle size of the quadriceps.