Photo: Steve taking the inside line to a third place podium finish at the 2008 Hopkins Raspberry Criterium. Like the namesake chariot races from Roman times, riding the fine line between control and mayhem.

Interval training is not just for competitive athletes. A number of years ago I took on a client in his early fifties who had broken all his ribs on one side of his body from a fall off, and on to, a ladder. He was overweight, out of shape, and was prone to vagus nerve overstimulation where the heart temporarily slows down depriving the brain of oxygen, causing him to lose consciousness. Over time, through strength training combined with interval training, he gained strength, reduced his weight, improved his cardiovascular fitness, and minimized incidents of vagus nerve overstimulation. Today he is stronger, leaner and back running.

In this What I Learned article, I will define interval training, how it works and the benefits you can expect from incorporating interval training into your fitness program.

What is Interval Training?

Interval training uses short bursts of high energy activity characterized by high heart rates followed by low intensity activity and lower heart rates. These cycles are repeated a number of times. The variables are duration of the high energy cycles and rest cycles, the intensity of each cycle, and the number of times the cycles are repeated. Interval training has been used for years to improve the performance of elite endurance athletes.

I incorporate intervals into training programs for my clients ranging in age from early fifties to mid-eighties; and ability from elite athletes to those who have not had a regular exercise program for years. My programs utilize body weight and light weight exercises. The goal is not to build muscle mass, but muscle strength. We work on the ability of joints and soft tissues to handle stress; and improving mobility, flexibility, and balance. By doing these exercises in intervals of varying intensity and duration, we improve cardiovascular fitness as measured by VO2 Max, a measure of the capacity of your body to transport and utilize oxygen. The higher your VO2 max, the greater your ability to handle stress. Studies show the higher your VO2 max the better your chance at avoiding lifestyle diseases like heart disease, Type II diabetes and cancer.

Interval training is critical for improving the competitive performance of master athletes and helping all of us to live a healthier and more active life.

How Does Interval Training Work?

Most of think of cardio fitness as the ability of the heart to pump blood and oxygen throughout the body. Another component of fitness is the ability of your muscles to utilize the oxygen delivered. The muscles use oxygen to burn a variety of fuels such as sugars and fats. Short-term energy demand is met by burning sugar: blood glucose and muscle glycogen. Long term energy is supplied by burning fat. The problem for many people is that their bodies and poorly adapted at burning fat for fuel.

I had a client who was a cyclist and kept himself strong by lifting weights and flexible with yoga. He had low body fat and ate a healthy diet. His problem was at middle distance bike rides he would bonk. Toward the end of the ride he would hit a hill, and unable to sustain the pace, get dropped from the group. I tested his ability to burn fat and VO2 max. We found he was a poor fat burner with an average VO2 max.

Exercise works by stressing the body forcing it to adapt. Repeated over time, exercise remodels your body. The heart becomes a stronger pump and arteries more flexible. Tiny capillaries grow throughout the muscle delivering more blood to the muscles and the muscle themselves grow more mitochondria, the powerhouse cell of the muscle. Studies show that interval training activates the same pathways as long bouts of endurance training. Interval training is very efficient at activating the proteins that build more mitochondria. It is thought that interval training activates both slow and fast twitch muscles over a short period of time. Interval training leads to a faster adaption to exercise stress.

I had my client work on two types of interval training: low to moderate intensity to improve his body’s ability to burn fat; and high intensity intervals to improve his VO2 max. Over the course of three months we accomplished both objectives.

Interval Training and Aging

A 2013 study tracked the health of 786 French Tour de France cyclists and compared their mortality risk to the general population. The cyclists had a 41 reduction in mortality risk than the general population. In other words, the French cyclists lived an average of 6.3 years longer than the average French male.

As we age, our cardiovascular system becomes less efficient. Over time, our heart grows weaker and blood vessels stiffer. Studies show interval training improves cardiovascular fitness more than moderate intensity continuous exercise.  A landmark study in Sweden tested the impact of interval training versus continuous training. The average age of the subjects was seventy five. The interval group’s cardiovascular fitness increase three times as much as the continuous group. The increase was 45 percent for the interval group and 14 percent for the continuous group. The best indicator of overall health is cardiovascular fitness.

If you want to live a healthier and longer life, add interval training to your program

Interval Training and Weight Loss

In the United States, an estimated 75 million Americans are insulin resistant and 30 million have type 2 diabetes. The inability of your body to control your blood sugar leads to serious health complications. Exercise can mitigate and even reverse type 2 diabetes. Interval training forces muscle cells to suck glucose out of the blood. Studies show interval training can reduce average blood glucose concentrations by 13 percent. Insulin resistance is a major cause of weight gain. See my article Why It’s So Hard to Lose Weight:

Interval training improves the body’s ability to burn fat as a preferred fuel. Becoming better at burning fat is a key strategy for weight loss. Check out my article Get Lean and Stay Lean:


Interval training is a core fitness strategy for myself and my clients. It works. I have seen the benefits in the lab of real life. I use it to train for competitive cycling; Nordic and Alpine skiing; backpacking and mountain climbing. The results are amazing—improved strength, VO2 max, fat burn, and overall health. Most importantly, I am able to do the sports and activities I love into my late sixties and, hopefully, beyond.

In the next edition of What I learned, I will detail how to incorporate interval training into your fitness program depending on your age, fitness, and goals.    

Photo: Steve with four gold medals in four cycling events at the 2017 Minnesota Senior Games.

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