Why muscles get sore after a long break from the gym: new study findings

Research suggests muscles remember the damage that first workout after a break caused and react, rather as the immune system does to disease, the next time you hit the gym

PUBLISHED : Friday, 12 February, 2016, 10:00am
UPDATED : Friday, 12 February, 2016, 10:00am

The first time back to the gym after a long break usually results in sore muscles, but subsequent trips are generally less painful – and a new study explains why. Exercise scientists at Brigham Young University have found that T-cells – the same type of white blood cells that respond to infections – play a role in repairing muscles. The researchers put 14 men and women through two vigorous rounds of exercise on an isokinetic dynamometer machine, 28 days apart. “All of them got really sore,” says Robert Hyldahl, assistant professor of exercise science at BYU. Before and after each bout of exercise, the team took muscle biopsies from the subjects and then used immunohistochemistry and microscopy to analyse the muscle tissue. They found an expected increase in certain white blood cells and the presence of T-cells after the second bout of exercise. This suggests the muscle seems to remember the damaging result and reacts similarly to when the immune system responds to antigens – toxins, bacteria or viruses. The researchers were also surprised to find inflammation actually increased after the second round of exercise, suggesting inflammation itself probably does not worsen exercise-induced muscle damage. Hyldahl says: “Some people take anti-inflammatory drugs such as Ibuprofen and Aspirin after a workout, but our study shows it may not actually be effective.“

Sustained aerobic exercise increases adult neurogenesis in the brain

Want to boost your learning ability? The best workout is aerobic exercise such as running, say Finnish researchers. In tests on rats, the scientists from the University of Jyväskylä found rats that ran long distances had the most generation of neurons (neurogenesis) in the hippocampus, a brain structure important in learning, compared to rats that did resistance training (no effect) or high-intensity interval training (minor effect). Compared to sedentary animals, rats that voluntarily ran long distances on a running wheel and also had a genetic predisposition to benefit from aerobic exercise had 2-3 times more new hippocampal neurons at the end of the experiment. The exercise training period was 6 to 8 weeks, during which control animals remained in sedentary conditions in the home cage. According to previous research, the new hippocampal neurons produced as a result of neurogenesis are needed among other things for learning temporally and/or spatially complex tasks. It is possible that by promoting neurogenesis via sustained aerobic exercise, the neuron reserve of the hippocampus can be increased and thus also the preconditions for learning improved – also in humans.

Stress could help activate brown fat

A little stress could be helpful if you're trying to burn more calories. A new study has found that mild stress stimulates the activity and heat production by brown fat, the main function of which is to generate body heat by burning calories (opposed to white fat, which is a result of storing excess calories). To induce mild psychological stress, researchers had five healthy lean women solve a short maths test in the first run, but in the second run, the test was substituted with a relaxation video. To assess stress responses, the scientists measured cortisol in the saliva. To measure the activity of brown fat, the researchers used infrared thermography to detect changes in temperature of the skin overlying the main area of brown fat in humans (in the neck region). Although the actual maths tests did not elicit an acute stress response, the anticipation of being tested did, and led to raised cortisol and warmer brown fat. Both were positively correlated, with higher cortisol linked with more fat activity and thus more potential heat production. “A better understanding of the main factors controlling brown fat activity, which include diet and activity, therefore has the potential to introduce sustainable interventions designed to prevent obesity and diabetes,” says Professor Michael E Symonds from The School of Medicine, University of Nottingham and co-author of the study. “In future, new techniques to induce mild stress to promote brown fat activity could be incorporated alongside dietary and/or environmental interventions.”