Title: Comparing the Effect of Low-Load Resistance Exercise Training Versus High Intensity Interval Training on Muscle Endurance, Muscle Strength, Muscle Hypertrophy, VO2Peak and Anaerobic Performance
Thesis Supervisor: Cameron Mitchell
Committee members: David Wright, Robert Boushel
Defence Chair: Tania Lam
Abstract: Low-load resistance training (LLRT) increases low-load absolute local muscle endurance (LME), however the physiological mechanisms inciting these adaptions are poorly understood. High intensity/sprint interval training (HIIT/SIT) increases muscle capillarization, mitochondrial content and function (hypothesized mechanisms of LME), yet minimal research has determined the effect of HIIT on low load absolute LME. LLRT and HIIT/SIT fall the closest to one another on the strength-endurance exercise continuum. Therefore, the largest potential “cross-over” effect could exist for these interventions, whereby HIIT/SIT and/or LLRT may simultaneously increase, muscle endurance, muscle strength, muscle mass and maximal aerobic fitness. Untrained healthy individuals aged 19-30 were recruited (1010 completed). Participants legs were randomized to a LLRT program or HIIT/SIT protocol over a 10-week period (2-3x/week). Single-leg knee extension 1-RM, single-leg VO2Peak, leg/thigh lean mass (DEXA), vastus lateralis thickness (ultrasound), low load absolute local muscle endurance, isometric knee extension and flexion (90°), isokinetic knee extension and flexion (60°/sec) and 30 second maximal kicking performance were assessed pre and post training. An overall effect of time was observed for 1-RM strength, VO2Peak power output, mean and peak power on the 30 second maximal kicking performance and repetitions completed at 30% pre-training 1-RM. A moderate-large (0.68) and small-moderate (0.48) effect size was observed in favor of the LLRT group for change in repetitions completed at 30% pre-training 1-RM and isometric knee extension strength respectively. A large (0.93) and moderate-large size effect was observed in favor of the SIT/HIIT group for change in vastus lateralis muscle thickness and mean power on the 30 second maximal kicking performance test respectively. LLRT induces greater gains in low-load absolute LME and isometric strength while HIIT/SIT promotes larger increases in muscle thickness and anaerobic performance.