THE EFFECT OF INTERMITTENT CYCLE TRAINING TIME AND INTENSITY ON AEROBIC CAPACITY

Introduction: Aerobic exercise capacity outperforms established clinical risk factors such as smoking, hypertension, obesity and diabetes in predicting all-cause mortality (Myer et al., 2004). ‘Lack of time’ is the most commonly cited barrier to sufficient amounts of physical activity (Trost et al., 2002). High intensity interval training (HIT) is a time-efficient alternative to moderate intensity continuous training (MICT), but the feasibility for exercise-naïve individuals has been questioned. Success has depended on vigorous encouragement by the researchers and the presence of expensive specialised cycle ergometers. Aim: To investigate whether two popular HIT protocols (30HIT and 60HIT) can increase aerobic exercise capacity without verbal encouragement or specialised cycle ergometers, such that HIT interventions can be delivered in a real life setting independent of instructors. Methods: Twenty-eight previously sedentary males (n=6) and females (n=22) aged 18-55 participated (28±2 y, BMI 25±1 kg.m2). In a randomised counterbalanced cross-over design, participants completed either 6 weeks of 30HIT (4-8x30s with 120s active recovery) or 60HIT (6-10x60s with 60s active recovery). Training sessions were completed on a Wattbike, 3 times per week. Participants were told to reach > 80% of maximal heart rate (HRmax). VO2peak and Watt max were assessed pre and post each intervention, with a 4-6 weeks wash-out period between interventions. Results: VO2peak increased post intervention in 30HIT (37±1 to 38±1 ml.min-1.kg-1) and 60HIT (35±1 to 38±1 ml.min-1.kg-1). There was a significant main effect of training on VO2peak (P < 0.001), with no difference between training modes (P=0.849). When normalized to Watt max those participants producing higher peak power output (PPO) improved their VO2peak significantly more than those producing a low PPO, irrespective of group (30HIT P