Wayne L. Westcott: Interval training provides a boost

Wayne L. Westcott

As we age, we lose muscle at the rate of 5 to 7 pounds per decade, unless we perform regular strength training.

However, even when we do progressive resistance exercise, we experience a change in our muscle tissue as we grow older.

Under normal circumstances, our fast-twitch muscle fibers become smaller (atrophy) and may even disappear in more advanced years. As this process continues, we have a lower percentage of fast-twitch muscle tissue, which definitely decreases our power performance.

The fast-twitch fibers are principally responsible for fast movements and powerful actions, such as sprinting, jumping, throwing and striking. As these fibers atrophy, our ability to perform fast movements and powerful actions is reduced proportionately. That is, we can’t run as fast, jump as high, throw as hard or swing the golf club/tennis racquet as forcefully.

Can we do anything to maintain our fast-twitch muscle fibers as we age? Yes.

Step one is to perform strength exercises two or three days each week. This will maintain/increase muscle mass and enhance both your slow-twitch and fast-twitch muscle fibers.

Step two is to perform medicine ball exercises to directly target fast-twitch fibers in the upper body muscles. Unlike standard strength training that is best performed at slow- to moderate-movement speeds, medicine ball throws can be safely performed at fast-movement speeds because you release the ball at the end of each throwing action.

Step three is to add interval training and sprinting to your standard aerobic activities to stimulate fast-twitch fibers in your leg muscles.

INTERVAL TRAINING AND SPRINTING

Most of us follow a familiar pattern during our endurance exercises. We warm up for about five minutes at a slow pace (running) or with low resistance (stationary cycling), then we train at a moderate effort level for 20 minutes, and then we cool down for about five minutes.

While this pattern is excellent for promoting cardiovascular fitness, it has little impact on our fast-twitch muscle fibers. Without faster-paced training, the ability to move our limbs quickly will gradually decline with age.

Interval training and sprinting are perhaps the two most effective means for improving this situation. Both of these techniques can be practiced in most aerobic activities, such as running, cycling and rowing.

Start with interval training, which divides your endurance exercise session into alternating periods of lower-effort (slower-paced) and higher-effort (faster-paced) performance.

For example, instead of running on the treadmill at 6 mph for 20 minutes, you could run at 7 mph for 4 minutes, then run at 5 mph for 4 minutes, alternating faster and slower segment throughout your 20-minute training session. As you become more fit, you can progress to faster intervals, such as 2 minutes at 8 mph, followed by 2 minutes at 4 mph, again alternating higher-effort and lower-effort segments throughout a 20-minute workout.

The faster the running speed, the more involvement of fast-twitch muscle fibers.

To maximize the impact on your fast-twitch muscle fibers, you need to approach sprinting speed, which is not recommended for treadmill training. My preference is to perform a couple of 50- to 100-yard sprints after I complete my outdoor runs. This is an exhilarating way to finish an endurance exercise session, and it provides an excellent training stimulus for the fast-twitch muscle fibers. Of course, it is important to cool-down gradually after the sprints.

You can apply the same interval training and sprinting principles to other aerobic activities, such as stationary cycling.

For example, instead of pedaling 70 RPMs at 100 watts for 20 minutes, you could alternately pedal at 125 watts for 3 minutes, then at 75 watts for 3 minutes throughout your cycling session. As for sprinting, you could finish your workout with a couple brief bouts (15 seconds) of fast pedaling (90 RPMs) at the higher resistance.

It is not necessary to do interval training or sprinting every workout. However, I recommend at least one interval training and/or sprinting session each week.

In addition to stimulating your fast-twitch muscle fibers, interval training is more effective than steady-state exercise for improving your cardiovascular endurance.

Although your short sprinting segments will not increase your aerobic capacity, they provide a greater training stimulus to your fast-twitch muscle fibers for improved power performance.

It is more challenging physiologically and psychologically to do interval training and sprinting. However, the benefits in terms of physical fitness and activity performance are well worth the effort. Please check with your doctor before beginning any new exercise program.

Wayne L. Westcott, Ph.D., teaches exercise science at Quincy (Mass.) College and consults for the South Shore YMCA. He has written 24 books on physical fitness.