Characterizing the Heart Rate Response to the 4 × 4 Interval Exercise Protocol.

Justin J Acala,Devyn Roche-Willis,Todd A Astorino

doi:10.3390/ijerph17145103

Justin J Acala, Devyn Roche-Willis + Show 1 more

Open Access

https://doi.org/10.3390/ijerph17145103

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Abstract

High intensity interval training is frequently implemented using the 4 × 4 protocol where four 4-min bouts are performed at heart rate (HR) between 85 and 95% HR max. This study identified the HR and power output response to the 4 × 4 protocol in 39 active men and women (age and VO2 max = 26.0 ± 6.1 years and 37.0 ± 5.4 mL/kg/min). Initially, participants completed incremental cycling to assess VO2 max, HR max, and peak power output (PPO). They subsequently completed the 4 × 4 protocol, during which HR and power output were monitored. Data showed that 12.9 ± 0.4 min of 16 min were spent between 85 and 95% HR max, with time spent significantly lower in interval 1 (2.7 ± 0.6 min) versus intervals 2–4 (3.4 ± 0.4 min, 3.4 ± 0.3 min, and 3.5 ± 0.3 min, d = 2.4–2.7). Power output was highest in interval 1 (75% PPO) and significantly declined in intervals 2–4 (63 to 54% PPO, d = 0.7–1.0). To enhance time spent between 85 and 95% HR max for persons with higher fitness, we recommend immediate allocation of supramaximal intensities in interval one.

Highlights

High intensity interval training (HIIT) is characterized by repeated efforts (1–4 min in duration) at near-maximal to maximal intensities interspersed with recovery [1]
heart rate (HR) gradually increased during each interval, and the HR value upon initiation of each interval steadily increased during the session
Time spent between 85 and 95% HR max increased during the session (p < 0.001), and post hoc analyses showed that time in intervals 2 through 4 was significantly higher than in interval 1 (d = 2.4–2.7) (Table 2)

Summary

Introduction

High intensity interval training (HIIT) is characterized by repeated efforts (1–4 min in duration) at near-maximal to maximal intensities interspersed with recovery [1]. Compared to moderate intensity continuous training (MICT), completion of HIIT induces superior increases in maximal oxygen uptake (VO2 max) in healthy adults [2], as well as persons with chronic disease [3], which benefits health, considering the strong relationship between VO2 max and mortality [4]. In inactive men, Nybo et al [5] demonstrated greater increases in VO2 max in response to 12-weeks of HIIT than that acquired with MICT. Results in obese young women exhibit significantly greater increases in VO2 max and reductions in fat mass with sprint interval training compared to MICT of equal energy expenditure [6]. HIIT workloads as low as 60% of peak power output (% PPO)

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