“I was feeling stressed from work when I started, but now I feel much better.” I hear this remark frequently from my personal training clients. They also tell me that one of the many benefits of resistance training is both feeling better after one session and controlling stress over time. What’s the evidence that resistance exercise reduces stress? And if exercise does reduce stress, what is it about exercise, and resistance training in particular, that reduces stress?

Multiple studies demonstrate the anxiety-reducing effects of single bouts of resistance exercise, depending on the intensity of the workout. In a 24-week, community-based intervention, researchers observed greater decreases in anxiety in older participants (65–75 years) performing exercise at 50% their maximum weight on an exercise, to those exercising at 80%. In contrast, a work-place intervention using light resistance training (30% 1RM) failed to reduce anxiety outcomes. To reduce stress, make sure the workout isn’t too hard or too easy. 

A number of studies have demonstrated the long-term benefits of resistance exercise. (Resistance exercise includes free weights, machines, bodyweight exercises, and bands.) Several studies examined the effects of resistance exercise on anxiety in older populations (>60 years). These studies indicate that participating in regular resistance exercise decreases stress for older populations. 

One study looked at whether resistance exercise led to reduced anxiety on healthy people with low levels of anxiety (New York Times, July 26, 2021). To find out, researchers recruited 28 physically healthy young men and women and tested their current moods, particularly whether the volunteers felt anxious. All the participants scored in a healthy range on detailed anxiety questionnaires. Researchers asked half of the participants to continue with their normal lives as a control group. The other half began to weight train, a practice with which few were familiar.

After eight weeks of training, the weight trainers scored about 20 percent better on the tests of anxiety than the control group. They had started with low levels of anxiety to begin with, but felt even less anxious after eight weeks of training.

The researchers didn’t study why the weight lifting group experienced less anxiety, but they suspect increased physical and psychological potency has something to do with it. The lifters became stronger over time and able to lift heavier weights. “Feelings of mastery may have occurred” leaving people feeling generally more capable of coping. 

The mental benefits of exercise also have a neurochemical basis. Exercise reduces levels of the body's stress hormones, such as adrenaline and cortisol. Exercise also stimulates the production of endorphins, chemicals in the brain that are the body's natural painkillers and mood elevators. Endorphins are responsible for the "runner's high" and for the feelings of relaxation and optimism that accompany many hard workouts.

Behavioral factors also contribute to the emotional benefits of exercise, including resistance training. As one’s waistline shrinks and strength and stamina increase, a person’s self-image improves. Exercisers earn a sense of mastery and control, of pride and self-confidence. Their renewed vigor and energy help them accomplish tasks, and the discipline of regular exercise helps achieve other important lifestyle goals.

By preventing bodily illness, exercise reduces the stress caused by poor health. Regular physical activity lowers blood pressure, improves cholesterol, and reduces blood sugar. Exercise cuts the risk of heart attack, stroke, diabetes, colon and breast cancers, osteoporosis and fractures, obesity, depression, and even dementia. Exercise slows the aging process, increases energy, and prolongs life.

In the middle of a stressful period, it’s easy to put your workouts aside. The best time, however, to work out is when you’re experiencing stress. In a less anxious state, you can deal with stressful situations more rationally and make better decisions.