Effects Of Exercise Modality And Structure On Physiological And Perceptual Responses To Exercise

Abstract

Moderate intensity continuous training (MICT) and high intensity interval training (HIIT) in the form of cycling and running, are effective types of exercise for improving fitness and health. However, cycling may cause higher levels of local muscle fatigue due to the greater contribution of anaerobic metabolism, while more muscle mass is active during running, resulting in higher oxygen uptake (VO2) and energy expenditure. PURPOSE: To examine the effects of exercise modality (cycling vs. running) and structure (continuous vs. interval exercise) at an individualized exercise intensity, on physiological and perceptual responses. METHODS: Seven healthy young individuals (3 M and 4 F, age = 21 ± 1 years) performed four 20 min trials in random order: continuous cycling and running (MICT) at an intensity corresponding to 80% of the individual ventilatory threshold (VT) and intermittent cycling and running (HIIT) including 10 x 1 min bouts at 120% VT, with 1 min active recovery at 60% VT. Blood lactate concentration was measured at rest, midway during exercise and 3 min after exercise, while VO2, heart rate (HR) and rating of perceived exertion (RPE) were measured continuously. Data were analyzed using 3-way repeated measures ANOVA. RESULTS: VO2max (40.0 ± 5.8 vs. 36.0 ± 5.3 ml/kg/min, p<0.001) and VT (70.8 ± 7.6 vs. 51.4 ± 4.2 %VO2max, p<0.001), were higher in running than cycling. This resulted in energy expenditure that was highest in HIIT and MICT during running (217 ± 47 and 199 ± 61 kcal, respectively, p<0.001) and lowest in HIIT and MICT during cycling (142 ± 19 and 142 ± 17 kcal, respectively). Average HR was higher in running versus cycling (159 ± 15 and 138 ± 9 bpm, p=0.008) and in HIIT versus MICT (155 ± 10 and 142 ± 11 bpm, p=0.03), but there was no 3-way interaction (p=0.79). In contrast, blood lactate concentration was not different between cycling and running (p=0.44), while RPE was slightly higher during running than cycling (2.75 ± 1.15 and 2.10 ± 1.0 units, p=0.03) CONCLUSIONS: Running, especially in the form of HIIT at an individualized intensity close to VT, results in greater energy expenditure, while blood lactate and RPE are similar to cycling HIIT or MICT. Thus, HIIT running at this intensity may be used as an effective and tolerable exercise modality for healthy individuals when available time is limiting.