What is the Optimal Intensity of a 60s/60s High Intensity Interval Training (HIIT) Program?
Title: Acute Cardiopulmonary and Metabolic Responses to High-Intensity Interval Training Protocols Using 60 s of Work and 60 s Recovery
Authors: Rozenek et al
Journal: Journal of Strength and Conditioning Research
Objective: The purpose of this study was to examine the acute physiological responses to 60s/60 s x 10 HIIT protocols using several combinations of work and recovery intensities.
High Intensity Interval Training or HIIT, is a form of exercise that involves alternating periods of intense training with periods of rest or low intensity training. This form of training is becoming increasingly popular among both professional athletes as well as more casual fitness enthusiasts.
Compared to traditional training regiments, two advantages include the ability to workout at higher intensities and to perform more total work. Studies have shown that you can achieve the same or more cardiopulmonary and metabolic changes with an HIIT workout than a moderate intensity workout in less time.
Optimization of HIIT remains a challenge. For example, is 20 seconds on and 20 seconds off better, the same or worse than 60 seconds on and 60 seconds off? Previous studies have shown 60 seconds of work and 60 s recovery repeated for 10 times has previously been found to produce beneficial cardiopulmonary, cellular, and metabolic adaptations in healthy and at-risk populations. The authors sought to shed further light on this question.
11 healthy adults (average age 26)
They performed 4 HIIT trials on separate days at varying percentages of peak power output that consisted of the following work/recovery intensities:
- (a) 80% PPO/0% PPO (80/0);
- (b) 80% PPO/50% PPO (80/50);
- (c) 100% PPO/0% PPO (100/0);
- (d) 100% PPO/50% PPO (100/50)
Peak oxygen uptake (VO2 Peak), peak heart rate, peak power output, peak blood lactate measured at baseline before the study started and then measured during each protocol trial.
Compared with the other protocols, the 100/50 protocol produced higher (p < 0.05) peak, average, and nadir %V_ O2 peak. (In other words the 100/50 protocol had the greatest oxygen consumption and is a reflection of aerobic metabolic activity). However, the 100/50 protocol could not be completed by all the subjects.
Interestingly, increasing the recovery period from 0% to 50% of PPO had the greatest effect on %VO2 peak.
All the trials produced %V_ O2 peak and %HR peak values that were within exercise intensity ranges (45–90% V_ O2max; 65–90% HRmax) recommended by the American College of Sports Medicine for improvement of cardiopulmonary function (except nadir values resulting from the 80/0 trial).
Similar average HR and peak HR, blood lactate, and %V_ O2 peak values were produced by 80/50 and 100/0 protocols. However, the average %V_ O2 peak was significantly higher (~9.3% absolute) in 80/50.
These studies help quantify the effects of changing how hard you exercise during either your work or recovery intervals.
The 100%/ 50% PPO protocol appeared to have the most significant cardiopulmonary and metabolic effects, but was difficult to complete for some participants.
The other protocols also proved effective and probably are best suited for individuals at the low to moderate end of the fitness spectrum.
Rozenek, R., Salassi, J. W., & Pinto, N. M. (2016). Acute Cardiopulmonary and Metabolic Responses to High-Intensity Interval Training Protocols Using 60 s of Work and 60 s Recovery. Journal of Strength and Conditioning Research, 30(11), 3014-3023. doi:10.1519/jsc.0000000000001414