By David Kiefer, MD, Editor

Clinical Assistant Professor, Department of Family Medicine, University of Wisconsin; Clinical Assistant Professor of Medicine, Arizona Center for Integrative Medicine, University of Arizona, Tucson

Dr. Kiefer reports he is a consultant for WebMD.


  • One minute of maximum exercise in 10 minutes (three 20-second maximum cycling efforts separated by two minutes of low-intensity cycling) is comparable to 45 minutes of sustained cycing (70% maximum exercise) with respect to cardiovascular and metabolic parameters.

SYNOPSIS: Sedentary men achieved similar cardiometabolic improvements after 12 weeks of either short-duration, high-intensity exercise or the standard 45 minutes of sustained moderate-intensity exercise.

SOURCE: Gillen JB, Martin BJ, MacInnis MJ, et al. Twelve weeks of sprint interval training improves indices of cardiometabolic health similar to traditional endurance training despite a five-fold lower exercise volume and time commitment. PLoS One 2016;11:e0154075.

It almost sounds too good to be true. We can exercise less and still reap the cardiovascular benefits of extended moderate-intensity aerobic effort? Sign me up! Gillen et al, in a study that received widespread media coverage, compared sprint interval training to moderate-intensity training; the former involved one minute of intense exercise (3 x 20 seconds at 100% maximum heart rate) within 10 minutes, whereas the latter was the standard 45-minute continuous exercise (70% maximum heart rate) regimen, often recommended for preventive health and therapeutic interventions. Twenty-seven sedentary men (nine in the intense group, 10 in the moderate group, six controls) exercised three times weekly for 12 weeks.

Cardiometabolic parameters were tested pre- and post-intervention, and are listed and resulted in Table 1. Essentially, the improvements in the measurements were comparable (significant P values for intra-group comparison and no difference for inter-group comparisons) between the intense and moderate exercise groups. The researchers also measured skeletal muscle mitochondrial content, estimated mostly by the activity of citrate synthase (mmol/kg protein/hr), and found that the intense group increased by 48% and the moderate group increased by 27%, both of which were higher than the control group (P < 0.001).

The authors tie their results into the greater picture of how to improve cardiovascular risks (measurements of cardiovascular fitness have some correlates with this) and insulin resistance, and albeit a short duration, these results are intriguing. With an ever more sedentary population, the demographic studied here is likely relevant to our patients, and the intervention produced results that were meaningful, certainly in the short term, and, hopefully follow-up research will show in the long term. Encouraging lifestyle change can be a challenge, but perhaps this high-intensity, short-duration approach will appeal to some people, and help them along the road to better cardiometabolic health. Obviously, this regimen would need to be tailored to someone’s physical abilities (a swift move from sedentary to high-intensity could lead to injury or worse), probably best done, at first, under the supervision of a professional. This could be the breakthrough that people need to be more active in their busy lives. Overall, although it appears that less is not actually more, at least less duration (more intensity) of exercise leads to the same outcomes.

Table 1: Cardiometabolic parameters for the intense and moderate excercise groups and control group


Intense Exercise

Moderate Exercise









Peak oxygen uptake (mL/kg/min)






“no change”; value not given

Insulin sensitivity index (microU/mL)