Longer vs. Shorter Intervals Elicit Similar Cardiovascular But Significantly Different Metabolic Responses During Interval Cycling
Andrew Scott, Christopher Bennett, Jasmine Lasslett & Daniel Reeves. University of Portsmouth, Portsmouth, Hampshire, UNITED KINGDOM.
PURPOSE: Interval training (IT) is utilised to optimise adaptations to exercise training with some recent research interest in whether low volume IT is efficacious. Therefore the purpose was to determine whether using shorter intervals would stimulate similar acute cardiorespiratory responses to longer intervals.
METHODS: Nine low active participants (8 males, 1 female) performed an incremental cycle test and then two experimental IT trials on an electronically-braked cycle ergometer at least 48 hours apart in a counter-balanced repeated measures study. Ventilatory threshold (TVent) and peak oxygen uptake (V̇O2peak) were calculated from the incremental cycle test. The participants then completed the two IT trials which consisted of six blocks of work and recovery at a ratio of 2:3 minutes for LONG, and a ratio of 1:1 minutes for SHORT, for work and recovery, respectively. The ‘work’ intensity of each IT trial was calculated as 50% of the difference between V̇ O2peak and Tvent (∆50%) and the ‘recovery’ intensity was calculated as 80% of Tvent. SHORT was 12 minutes and LONG was 30 minutes, plus 5 minutes warm-up and 2 minutes cool down. Oxygen uptake (V̇O2), respiratory exchange ratio (RER), heart rate (HR) and power (W) were recorded continuously. Rating of perceived exertion (RPE) was collected at the end of each interval. Blood lactate [La-] and systolic blood pressure (SBP) were recorded pre and post-exercise. Rate-pressure product (RPP) and energy expenditure (EE) were calculated. Participants reported which was their preferred session. Paired samples analyses were applied to quantitative data.
RESULTS: Mean RPE during work (13 ± 2 vs. 13 ± 3; p=0.421), mean V̇O2 (2234 ± 404 vs. 2258 ± 483 mL-1∙min-1; p=0.471), RPP (25412 ± 2456 vs. 24234 ± 2363; p=0.346), SBP (150 ± 12 vs. 140 ± 13 mmHg; p=0.204) and [La-] (7.30 ± 1.86 vs. 6.46 ± 2.15 mmol∙L-1; p=0.416) were not significantly different between SHORT and LONG. However, mean RER (1.02 ± 0.09 vs. 0.99 ± 0.04; p=0.002) was significantly lower and energy expenditure (287 ± 81 vs. 473 ± 93 kcal; p>0.001) was significantly greater following LONG. SHORT was preferred to LONG by all 9 participants.
CONCLUSION: LONG elicited significantly different metabolic responses with similar cardiovascular responses to SHORT but was perceived as less enjoyable.
No grant funding was obtained for this study.
Keywords: Acute, Interval, Cycling, Volume, Cardiorespiratory