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Elizabeth Quinn, an exercise physiologist and fitness trainer, in her blog on sports medicine at about.com, reports that resting after exercise helps to repair tissues that were stressed during exercise and to replace lost energy stores. Here she is referring to the day or days off from intense exercise needed in both recreational and competitive sports. She also reminds people that there are psychological aspects to rest and recovery, specifically the use of our body sense.
"Symptoms of overtraining often occur from a lack of recovery time. Signs of overtraining include a feeling of general malaise, staleness, depression, decreased sports performance and increased risk of injury, among others. The most important thing you can do to recover quickly is to listen to your body. If you are feeling tired, sore or notice decreased performance you may need more recovery time or a break from training altogether. If you are feeling strong the day after a hard workout, you don't have to force yourself to go slow. If you pay attention, in most cases, your body will let you know what it needs, when it needs it. The problem for many of us is that we don't listen to those warnings or we dismiss them with our own self talk (‘I can't be tired, I didn't run my best yesterday' or ‘No one else needs two rest days after that workout; they'll think I'm a wimp if I go slow today.')."
I like this approach because it brings body sense into the loop of understanding exercise physiology. We know a lot about the metabolism and muscle of exercise but less focus is placed on how exercise feels in our bodies. Why is the body sense of exercise important? As I've explained in previous posts in this blog, feeling one's body during any type of activity enhances the body's ability to most effectively marshal its resources to enhance health and well being.
This is because the neural circuits for awareness of the body's sensations and emotions are directly linked into the regulatory-executive zones of the prefrontal cortex, to limbic and paralimbic emotional areas, to the hypothalamus (ANS, hormone, immune function) and the brain stem regulatory centers which finally link into body systems that energize, repair, regulate and rejuvenate body tissues. Your body can do some of this on its own, without your paying attention. If you are also aware of your body as it does these things, it supports and amplifies the ability of these regulatory networks to promote health and well-being.
In addition to whole days of rest and recovery after exercising, there have been recent press releases about the physiological benefits of taking brief rest periods during exercise, called interval training. In normal workouts, people exercise continuously for 30-60 minutes or longer, and then recover the remainder of the day or until the next workout day. Interval training, in addition to these long recovery periods between workouts, mixes short bursts of intense activity with short rest periods between them.
One study compared different groups of healthy male adults, each of which ran 5.9km on a treadmill 3 times per week for 8 weeks. One group had a normal continuous workout period, another did interval training of 4 minutes of activity and 4 minutes of rest, and another interval group did 15 seconds of activity followed by 15 seconds of rest. At the end of 8 weeks, the 4 X 4 minute group was performing at double the endurance of the other two groups. The 4 X 4 group also had better oxygen consumption, more cardiac output, were 10 percent stronger and 5 percent faster. Similar results have been found even in heart patients and in the elderly. Another study found that if people take regular rest breaks during a 40-60 minute workout, it increases their ability to metabolize fats.
These are dramatic effects and some are claiming that such findings could lead to a major shift in how people go about recreational exercise and endurance training. While reading these studies, however, I could not find any mention of a possible psychological component to explain these effects. In fact, these studies offered very little in the way of physiological explanation except to say that the 4 X 4 interval regimen increased oxygen uptake which is known to be the most important factor in building endurance.
The neural networks for body sense awareness are linked directly to brain stem centers for the regulation of breathing and heart rate via the phrenic and vagus nerves, and hypothalamic centers that regulate body temperature, arousal and rest via the autonomic nervous system and hormones like cortisol and oxytocin, and tissue development via growth hormones. The same neurohormonal network provides feedback to the body sense - via limbic and prefrontal emotional centers -- to create feelings of lethargy or strength, depression or elation, that, as Quinn points out, can accurately inform us about how much to exercise and when.
I tried an approximation of the 4 X 4 interval approach on a recent snowshoe trek. I wasn't keeping exact time but using my body sense. I started hiking uphill for a few minutes until I felt fatigue and oxygen hunger. Then I stopped to rest for a few minutes until I felt my heart and breathing slow to a more comfortable rate. Being in a snow covered evergreen forest allowed me to feel a lot more during the rest periods: the refreshing feeling of crisp mountain air in my lungs, the soothing of dappled sunlight and shadow, feelings of gratitude that I took the time to get out of the city and its routines.
Over the next hour or so of uphill travel, I noticed that the exertion periods became longer so I could travel farther without resting, and the rest periods became easier and more pleasurable, less focused on the mild panic of gasping for the thin high altitude air and my doubts about whether I could really make it to the end of the trail, and more infused with feelings of accomplishment, relaxation, and pleasure in just being in nature.
While this is not scientific proof, I'm convinced that active use of the body sense and its ability to boost regulatory body function is the "hidden" explanation for why interval training is so successful at enhancing performance. Four minutes, or whatever approximation of that works for your body, is probably the time it takes for us to feel deeply into our bodies; Deeply enough to activate those regulatory networks and long enough to feel their effects on speeding up or slowing down our arousal and exertion. Try it yourself and let me know how it works for you by posting a comment to this article.
