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Endurance Training/Cardiorespiratory

(50) No Differences in Acute Oxygen Consumption Response between High Intensity Interval Training Formats when Matched Based on W prime Expenditure

Friday, July 14, 2023
10:30 AM – 12:00 PM East Coast USA Time
Location: Milano III-IV
Abstract Details: High-intensity interval training (HIIT) has been shown to be an effective training modality to enhance maximal oxygen consumption (VO2max) and other submaximal performance metrics, such as critical power (CP). The manipulation of HIIT parameters to accelerate VO2 kinetics has garnered significant attention. Intervals with varying power outputs have been shown to induce a greater acute VO2 response compared to intervals with constant power outputs. However, interval sessions have been matched based on average power out during the intervals rather than metabolic metrics such as W prime (W’), which represents the finite amount of work that can be performed above CP.

Purpose: The purpose of this investigation was to compare the acute VO2 response of two different HIIT, fast start (FSHIIT) and steady power (SPHIIT) formats matched based on W’ expenditure.

Methods: Eight well-trained cyclists completed a total of four visits. On Visit 1, participants performed an incremental cycling test (ICT) to determine VO2max, peak power output (PPO), and the power which elicited VO2max (pVO2max). VO2max and pVO2max were verified using a square-wave bout verification protocol. Participants then rested for 30 minutes before completing the three-minute all-out test (3MT) to determine CP and W’, serving as a familiarization trial. On Visit 2, participants repeated the 3MT. CP and W’ from Visit 2 were used to establish parameters of the two HIIT sessions. Both sessions consisted of 3 X 4-minute intervals interspersed by 3 minutes of active recovery. Intervals were designed to deplete W’ by 60% (W’target) within each 3-minute intervals with the active recovery to allow for partial W’ replenishment. SPHIIT depleted W’target consistently throughout the 3-minute intervals (e.g., power output stayed constant). FSHIIT was designed to deplete W’target by 50% within the first minute of each interval, with the remaining 50% depleted evenly across the second and third minute of each interval (e.g., first minute was at a higher power then decreased for the second and third minute). VO2 was collected throughout each interval session. A two-way repeated measures analysis of variance (time and condition) was used to detect differences in peak VO2 response between minutes 1, 2, and 3 of each condition. Results are reported as mean ± standard deviation, with partial eta squared (η2) or cohen’s d (d) were used to determine effect sizes.  

Results: 8 cyclists (7 males, 27.1 ± 5.9 yrs, 179.0 ± 7.1 cms, 71.4 ± 12.6 kgs) completed the investigation with an average VO2max, pVO2max, CP, and W’ of 57.4 ± 7.0 ml/kg/min, 358.5 ± 40.9 watts (W), 288.1 ± 31.1 W, 12.8 ± 3.1 kilojoules, respectively. No significant time*condition interaction was present (f=.168, p=.847, η2=.027), but a significant main effect for time (f=32.2, p=.000, η2=.843) was present. Pairwise comparisons indicated a significant difference between minute 1 peak VO2 (35.0 ± 6.4 ml/kg/min) and minute 2 (43.4 ± 6.7 ml/kg/min, p=.003, d=1.2) and minute 3 (44.8 ± 9.3 ml/kg/min, p=.001, d=1.2). No significant differences were present between minute 2 and 3 (p >.05).

Conclusions: The results suggest that when HIIT formats are matched based on W’ expenditure there is no significant differences in peak VO2 achieved during each minute of the interval. PRACTICAL APPLICATIONS: Athletes and coaches can choose either interval with varying or constant power outputs and elicit similar acute responses in VO2.

Acknowledgements: None