Skeletal muscle pain and tenderness typically follow an unaccustomed bout of physical activity involving eccentric or lengthening contractions. The intensity of pain peaks between 24 and 72 h following the cessation of activity and subsides completely between 5 and 7 days after exercise. Delayed-onset muscle soreness (DOMS) refers to physical discomfort, while associated impairments to muscle strength and function reflect the occurrence of exercise-induced muscle damage (EIMD). The result is reduced performance and increased likelihood of further injury during the affected period. In beginners, DOMS may also reduce the likelihood of continuing exercise.
Despite its ubiquity in sport and exercise, the precise mechanism of DOMS remains uncertain. Potential mechanisms include EIMD, inflammation, and immune cell infiltration among others. More recently, evidence has emerged suggesting a greater role of intramuscular connective tissue damage in causing DOMS. Following an acute bout of eccentric exercise, the fascial connective tissue exhibits greater swelling than after a concentric exercise. Furthermore, this swelling was correlated with the severity of DOMS. This novel evidence may aid in directing strategies to mitigate the duration and severity of DOMS.
A variety of treatments for DOMS have been explored with varying degrees of efficacy. Massage has been shown to effectively mitigate DOMS following exercise as it passively increases muscle blood flow and reduces muscle oedema. Electrostimulation has also been shown to produce analgesic effects following unaccustomed exercise, although results are inconsistent. Differences in the treatment design may produce discrepant findings with longer duration, lower frequency stimulation alleviating DOMS, in contrast to shorter duration, higher frequency stimulation. Furthermore, lower-intensity longer-duration recovery modalities that promote muscle blood flow may partially ameliorate the ergolytic effects of DOMS. Based on these findings, active recovery consisting of low-intensity exercise following training which facilitates muscle blood flow might be expected to improve recovery from DOMS. However, active recovery strategies such as submaximal cycling or jogging following exercise has little effect on recovery from unaccustomed exercise. While these protocols do promote the muscle blood flow in the days following the bout of exercise, their intensity may be too great to allow for recovery of the muscle while their duration may be too low to produce a sustained effect. It has recently been shown that low daily step counts (\<5000/day) can interfere with the normal recovery from aerobic exercise and reduce the normal benefits to metabolism, highlighting that our habitual activity levels might be the most important variable in recovering from and adapting to the stress of exercise. Therefore, the purpose of this study is to investigate the effect of high (\>10,000 steps) and moderate (\<5,000) daily step counts on recovery from an unaccustomed bout of resistance exercise.
