Why your muscles get less sore as you stick with your gym routine: Unexpected immune system cells may help repair muscles -- ScienceDaily
"T-cells, up until recently, were not thought to enter healthy skeletal muscle," said lead author and grad student Michael Deyhle. "We hadn't planned on measuring them because there's no evidence that T-cells play a role in infiltrating damaged muscle tissue. It's very exciting."
The presence of the T-cells suggests that muscles become more effective at recruiting immune cells following a second bout of exercise and that these cells may facilitate accelerated repair. In other words, the muscle seems to remember the damaging insult and reacts similarly to when the immune system responds to antigens--toxins, bacteria or viruses.
The group was also surprised to find inflammation actually increased after the second round of exercise. Hyldahl, his students and many physiologists have long thought inflammation goes down after the second bout of exercise, contributing to that "less sore" effect.
Instead, the slightly enhanced inflammatory response suggests inflammation itself probably does not worsen exercise-induced muscle damage.
"Many people think inflammation is a bad thing," Deyhle said. "But our data suggest when inflammation is properly regulated it is a normal and healthy process the body uses to heal itself."
Adds Hyldahl: "Some people take anti-inflammatory drugs such as Ibuprofen and Aspirin after a workout, but our study shows it may not actually be effective. The inflammation may not be directly causing the pain, since we see that muscle soreness is reduced concurrent with increases in inflammation."