If you've ever channelled your pent-up frustrations into a lung-searing sprint or muscle-sapping strength workout, you already know that exercise is a powerful tool for stress reduction. But it turns out that stress and exercise – and mind and body more generally – are more tightly intertwined than previously thought.
Researchers at the Yale Stress Center recently published a study in the journal Medicine & Science in Sports & Exercise showing that people with higher levels of chronic mental stress take longer to recover their strength after workouts. The findings confirm that even the microscopic cellular processes that repair damage within your body are mediated by your state of mind – and that means that stress-reduction approaches like mindfulness and biofeedback could be as important to your physical fitness as crunches.
On its own, stress isn't necessarily bad, says Matthew Stults-Kolehmainen, the study's lead author. Exercise itself is a form of stress that triggers changes that make your body stronger, and the fight-or-flight mechanism, in response to sudden stress, helps you react to crises. But the system breaks down for chronically stressed people when they're confronted with an acute stressor like exercise.
"They may have the same reaction as less stressed individuals," Dr. Stults-Kolehmainen says, "but the toll on their bodies and minds after the threat has cleared may linger for a longer period."
The new study involved 31 undergraduates who completed a series of psychological assessments to determine their ongoing stress levels, and then performed an exhausting workout with heavy leg weights. An hour after the workout, the students with the lowest stress had regained 60 per cent of their lost leg strength, while the high-stress students had regained only 38 per cent.
The most straightforward explanation for the difference is that stress affects the levels of hormones like cortisol, in addition to many other chemicals, circulating in the body. These chemicals are essential to the inflammatory response that repairs damage throughout the body – and exercise, in many ways, is simply the process of inflicting minor damage to your muscles in order to have them rebuilt to be stronger.
Dr. Stults-Kolehmainen points to an earlier study, from researchers at Ohio State University, that directly tested the effects of stress on healing and repair. A group of 11 dental students agreed to have two 3.5-millimetre wounds punched in the roof of their mouth with a biopsy blade and scalpel – one during a vacation period, and the other three days before their first exam. The wounds took eight days on average to heal during vacation, and 11 days during exams – and not a single student healed more quickly during the exam period.
But the differences may depend on more than just hormones. The stressed-out students may also have been less likely to get enough sleep, eat well, and generally take care of themselves – all factors that can compromise the body's repair processes. And it's not clear whether stress leads to poor sleep and nutrition, or whether the arrow of causality points in the opposite direction.
"These factors often go hand in hand, causing a vicious cycle of stress, poor behaviours and further breakdown," Dr. Stults-Kolehmainen says.
Of course, no one chooses to be overstressed. If you're in that situation, the solution isn't to skip your workout – after all, exercise itself is a powerful tool to combat stress. Instead, make adjustments to your intensity and allow more time for recovery between sessions.
Dr. Stults-Kolehmainen and his colleagues at the Yale Stress Center also suggest deploying mindfulness and biofeedback techniques. The former can include yoga and relaxation training, while the latter involves monitoring – and learning to control – physiological measures such as breath rate, heart rate and muscular tension.
While there's plenty of evidence that these techniques are effective, he adds, the key is deploy them early and often, rather than waiting until you're in the midst of a full-blown crisis.
"There is no short-term fix for long-term stress," he says. "A single visit to a Zen master will not likely heal the long-term damage."
How to achieve mindfulness
The Yale Stress Center works with its patients to teach mindfulness-based stress reduction, an approach that guides patients to focus purposefully on the present moment. Here's a simple breathing exercise to try:
Pause for three minutes to observe your body breathing.
Follow the inhalations and exhalations, without trying to control or change anything.
Focus on feeling the sensations of breathing in the nostrils, the chest and the belly.
If your mind wanders, that's okay; just return your focus to your breathing.
Alex Hutchinson blogs about research on exercise at sweatscience.com. His latest book is Which Comes First, Cardio or Weights?