Considerable recent research is focused on the health and training effects of very
short duration high-intensity physical activity and the idea that we can rely on a
few high-intensity intervals as our only exercise and still improve our health and
fitness. High-intensity training (HIT), also called high-intensity interval training
(HIIT), requires repeated periods of maximum effort. This seems to be the most
efficient way to promote aerobic fitness and may improve exercise performance
to the same extent as traditional endurance training.

Research on high-intensity interval training (HIT or HIIT) has shown that repeated brief periods of maximum
effort exercise lead to the same muscle cell adaptations, fitness gains, and improved
cardiovascular function as prolonged low-intensity exercise, but in a much shorter
time. The 2018 Physical Activity Guidelines Scientific Advisory Committee
concluded that there is “moderate evidence to indicate that HIIT can effectively
improve insulin sensitivity, blood pressure, and body composition in adults. These
HIIT-induced improvements in cardiometabolic disease risk factors are comparable
to those resulting from continuous, moderate-intensity aerobic exercise. They are
more likely to occur in adults with overweight and obesity.”

The optimal time periods for maximum effort and recovery are not yet well established.
Martin Gibala, a professor of kinesiology at McMaster University in Hamilton,
Ontario, is one of the scientists who originated the HIT regimen. He suggests
that “a minute of hard effort followed by a minute of gentle recovery is effective.”153
However, it is not clear if a relatively few (16-30) minutes of high-intensity exercise
a week will confer the same health benefits as 75 minutes of vigorous exercise or
150 to 300 minutes of moderate intensity physical activity over a week as is recommended
by the Guidelines. One potential drawback of short, intense sessions is
that they don’t burn many calories and may not be as effective for weight loss and
maintenance as exercise schedules of longer duration. Another potential drawback
is the possibility of injury from the high level of stress placed on the musculoskeletal
and cardiovascular system.

One recent study evaluated twice weekly extremely short high-intensity training,
consisting of 10 × 6-second sprints with a one-minute recovery between each
sprint.154 Metabolic health (measured by an oral glucose tolerance test), aerobic
capacity (measured by incremental time to exhaustion on a cycle ergometer), and
physical function (evaluated by a get-up and go test, sit to stand test and loaded
50-meter walk) were determined before and after training. Following eight weeks
of HIT there was a significant improvement in aerobic capacity (8% increase in VO2
max), physical function (11% and 27%), and a reduction in blood glucose response
(6% reduction). The authors of the study concluded that the study demonstrated the
potential of HIT as a training intervention to improve skeletal muscle function and
glucose clearance as we age and that HIT needs to be performed only twice a week
to see major improvements in aerobic capacity, functional capacity and metabolic
health in an untrained middle-aged population. They suggest that HIT, lasting no
more than 11 minutes, may be used as a time-efficient method of reducing the risk
of disease and functional decline in middle age.

This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel.