The Effects of Stress on Exercise
Note from Doug:
This article was originally published in the May 2004 issue of Personal Fitness Professional, a leading personal training industry magazine. While the article was written for personal trainers, I believe you can personally benefit from considering the ideas and suggestions I present.
The Effects of Stress on Exercise
by Doug Jackson, M.Ed.,CSCS
Have you had two clients that recovered from exercise at drastically different rates? Maybe some clients could receive great results from strength training five to six days per week, while others seem to overtrain while performing the standard recommendation of strength training for three days per week? Has a client ever told you that they’ve gained a surprising amount of body fat during times of their lives when they were stressed?
Researchers are beginning to uncover answers to how non-exercise variables including lack of sleep, inadequate nutrition and high stress levels can significantly affect hormone levels that impact exercise recovery, weight management and health. Personal trainers must both understand how a client’s total stress levels affect their abilities to recover from exercise and how to monitor these variables when designing the volume, frequency and intensity of exercise programs.
The topic of stress has received much attention over the last several decades, and there is much controversy over exactly what stress is. There are questions related to good stress versus bad stress and exercise stress versus non-exercise stress. However, Hans Selye, widely-accepted as the pioneer of stress research, defined stress as "the nonspecific response of the body to any demand made upon it to adapt, whether that demand produces pleasure or pain."
Within the exercise domain, the interaction between exercise and stress gets more complicated. It’s generally believed that low-intensity exercise reduces stress, as compared with high-intensity exercise that tends to increase the release of stress hormones.
Fitness professionals that work with many people in applied settings have often believed that the client’s lifestyle drastically effects exercise progress and researchers are beginning to support this notion. In today’s high-stress world, people constantly have stress hormones over-stimulated in their bodies. This elevated stress response can lead to many of today’s health problems including CHD, hypertension, cancer, ulcers, lower back pain and headaches.
Clients who have chronically high-stress levels, inadequate sleep and poor nutrition will not be able to recover and adapt to exercise at the same rate that a person with optimal levels of stress, sleep and nutrition would. This is one possible explanation of why fat loss and fitness improvement may grind to a halt in some individuals, while other individuals continue adapting and progressing in their exercise programs. While we can counsel our clients of the importance of proper lifestyle choices, we may, at times, have to adjust our exercise recommendations based on our clients’ lifestyles.
When we delve into the physiology of the stress response, we find that there are three pathways of long-term stress response: the thyroxine axis, the vasopressin axis and the adrenocorticotropic axis (ACTH axis). The ACTH axis has been focused on most heavily. ACTH stimulates the adrenal glands to release corticoids including cortisol, costicosterone and cortisone.
Cortisol has been studied most extensively. Shawn Talbot, Ph.D., and author of The Cortisol Connection, states, “Over the long-term, elevated cortisol may be as detrimental to overall health as elevated cholesterol or elevated blood sugar.” Excessive cortisol release leads to a lowered testosterone: cortisol ratio, a prime marker of anabolic status and the ability to recover from exercise and build muscle. Further, as cortisol continues to increase, chances for muscle atrophy, impaired immunity, vitamin depletion and increased blood pressure occur.
Cortisol and Obesity:
As stress heightens, cortisol is released. While cortisol has beneficial effects on the body, the constantly high levels of it are problematic. According to the book Fat Wars, stress increases carbohydrate cravings due to the neurotransmitters NPY and serotonin. Thus, stress-related eating may increase caloric intake and increase body fat.
However, even when caloric increases are considered, cortisol still tends to promote the storage of fat, specifically to the abdominal area where it can quickly be utilized for the fight or flight response. Scientists have found an increased level of activity of the enzyme 11b hydroxysteroid dehydrogenase type 1 (11b HSD-1) in abdominal fat that they believe is the cause of the correlation between cortisol and abdominal fat. A recent study by Roland Rosmond and Per Bjourntorp found that stress-related cortisol secretion in men is strongly associated with abnormalities in glucose, insulin and lipid metabolism as well as abdominal obesity.
Exercise and Cortisol:
According to Andrew Fry, Ph.D., many people continue to increase both volume and intensity of exercise as they progress, although the body cannot adapt to this over a long period of time. Fry also states, as intensity of exercise goes up, exercise volume must go down, and vice versa. According to Fry, the testosterone:cortisol ratio, which is a marker of an individual’s anabolic status and recover ability, decreases as exercise volume increases.
During intensive strength training, the type of training used to transform bodies, the body enters a catabolic state where there is a net protein breakdown in the body. During this time, ACTH and cortisol are released to decrease muscle inflammation and to begin breaking down amino acids for the process of protein synthesis after exercise. While this is a natural and necessary response, excessive cortisol has been associated with overtraining syndrome.
Nutrition, Cortisol and Recovery Ability:
Nutrition has a powerful effect on recover ability. In a day where low-carbohydrate diets are popular, exercise professionals must consider how carbohydrate depletion impacts exercise response and recovery. When examining nutrition and stress response, we must look at a couple of different factors: total caloric balance and exercise nutrition. Cortisol is increased in a linear fashion as we drop below caloric balance. Thus, as people decrease their caloric intake to lose weight, cortisol tends to rise. Cortisol is also increased on low-carbohydrate diets when blood sugar levels drop too low.
During exercise, the body will breakdown an increased amount of muscle proteins as fuel if there is an inadequate supply of carbohydrates. However, it has been found that consuming a carbohydrate beverage during exercise accentuates the rise in cortisol levels and limits the amount of exercise-related immunosuppression.
Lack of Sleep and Cortisol:
Current research indicates that sleep deprivation can lead to an elevation in cortisol and is harmful to carbohydrate metabolism; changes which increase the chance of obesity. According to Michael Thorpy, Ph.D., and director of the Sleep Wake Disorders Center at Montefiore Medical Center in New York, "Sleep loss is associated with striking alterations in hormone levels that regulate appetite and may be a contributing factor to obesity. Anyone making a commitment to losing weight should probably consider a parallel commitment to get more sleep."
Putting It All Together:
Current research indicates that life-event stress, inadequate sleep and poor exercise nutrition can all lead to elevated levels of cortisol. Scientists believe that this excess cortisol may lead to a variety of health problems including impaired carbohydrate metabolism and increased abdominal fat. Within the exercise setting, excessive cortisol can lead to immunosuppression and overtraining syndrome. In addition, research indicates that lifestyle can influence exercise-related cortisol release. Thus, people with high lifestyle stress will release more cortisol during an intense bout of exercise as compared with someone who has a lower stress level.
If clients are experiencing high amounts of stress and cortisol release due to their lifestyles, it is in their best interests not to supplement that with excessive exercise-related cortisol release. Thus, it is recommended that personal trainers consider clients’ overall lifestyle when developing exercise volume and intensity guidelines for clients.
When striving to adjust client programs based on other stressors in their lives, assumptions have to be made, program designs may have to be adjusted and the personal trainer must be able to measure the results of these changes. In general, personal trainers can assume that clients who have a high degree of life stressors including high job stress, relationship stress, inadequate sleep and poor nutrition will not recover and adapt to exercise as quickly as someone who doesn’t face as many of these stressors. Thus, this high-stress environment should be taken into consideration when developing the exercise-related goals. Goals may have to be lowered or goal timelines extended to make sure the goal is achieved. Likewise, both volume, frequency and intensity of exercise may have to be lowered to a more appropriate level.
Once the program is implemented, the personal trainer should constantly be aware of the possible signs of overtraining syndrome within their clients. The easiest methods which are research supported are subjective measures of how the client is feeling. Is the client more sore than normal? Excessive soreness may indicate overtraining. How are they sleeping? Both restless sleep and chronic fatigue have been associated with overtraining. How is the client’s mood? Researchers have found that mood is an exceptional measure of overtraining within athletes.
In a research measure called the Profile of Mood States (POMS), researchers have found that most exercisers will have higher vigor as well as lower tension, depression, anger and fatigue than the general public. However, this can reverse during overtraining in which exercisers and athletes have shown lower vigor as well as higher tension, depression, anger and fatigue than the general public. A fitness professional would be wise to continuously assess these mood states in their clients and consider adjusting exercise program designs if clients begin showing the signs of overtraining.
In the future, fitness professionals will be more aware of how a client’s lifestyle choices outside of the exercise setting effect the results they obtain during the exercise session. In addition, fitness professionals will learn to educate their clients on how factors such as life stress, inadequate sleep and poor nutrition can affect the body’s physiology and exercise progress. Lastly, we will adjust exercise programs to meet the needs of each individual.
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