The primary aim of this study was to determine whether chronic mental stress moderates recovery of muscular function and somatic sensations: perceived energy, fatigue, and soreness, in a 4-day period after a bout of strenuous resistance exercise. Undergraduate resistance training students (n = 31; age, 20.26 ± 1.34 years) completed the Perceived Stress Scale and the Undergraduate Stress Questionnaire, a measure of life event stress. At a later visit, they performed an acute heavy-resistance exercise protocol (10 repetition maximum [RM] leg press test plus 6 sets: 80–100% of 10RM). Maximal isometric force (MIF), perceived energy, fatigue, and soreness were assessed in approximately 24-hour intervals after exercise. Recovery data were analyzed with hierarchical linear modeling growth curve analysis. Life event stress significantly moderated linear (p = 0.027) and squared (p = 0.031) recovery of MIF. This relationship held even when the model was adjusted for fitness, workload, and training experience. Perceived energy (p = 0.038), fatigue (p = 0.040), and soreness (p = 0.027) all were moderated by life stress. Mean perceived stress modulated linear and squared recovery of MIF (p < 0.001) and energy (p = 0.004) but not fatigue or soreness. In all analyses, higher stress was associated with worse recovery. Stress, whether assessed as life event stress or perceived stress, moderated the recovery trajectories of muscular function and somatic sensations in a 96-hour period after strenuous resistance exercise. Therefore, under conditions of inordinate stress, individuals may need to be more mindful about observing an appropriate length of recovery.
Alex’s Notes: We know that high-intensity exercise disrupts our “normal” to lead to adaptation. We also know that side-effects of this can be fatigue, soreness, and temporary reductions in muscular function. Usually these fade after 1-2 days, but not always. Regardless, these factors are important because they demonstrate a period when further muscle damage must be avoided and recovery optimized. Not all stressors are physical, however, and psychological stress has been shown to modulate physiological recovery. This is beautifully demonstrated in dental students who were lucky enough to have their mouth cut by a scalpel once during summer break and again during final exams; 100% of the subjects recovered more slowly during finals. Interestingly, the authors of the current study had previously published a paper that linked psychological stress to muscle recovery in the first hour after exercise. However, recovery is a multistep process that occurs over 24-96 hours, and the aim of this current study was to expand on the results of the previous and see just how muscle recovery is affected by both life stress and perceived stress.
The participants included 31 college-aged weight-training students that were randomly chosen from groupings in the lowest and highest stress scores, as assessed by a perceived stress scale completed by 210 students. The strenuous resistance training protocol involved six sets of a 45 degree leg press at a 3/2 eccentric/concentric tempo with a 1-second hold at full extension (knees not locked). The sets were performed to failure with the 1st set weight being the 10RM, and the 2nd set weight being 90% of that value. If the subject could perform more than ten reps during the second set, the 90% 10RM weight was maintained for the remaining sets, and if the subject couldn’t complete ten reps, the weight was dropped to 80% the 10RM for the remaining sets. Rest between sets was two minutes. Clearly this was a strenuous leg day; especially when you consider each set lasting roughly 60 seconds – that is a lot of time under tension.
Not surprisingly, all parameters of muscular function (maximal isometric force (MIF), squat jump, & cycle power) and energy were reduced, with increases in fatigue and soreness immediately post-exercise. However, the baseline stress level of the participants wasn’t related to these immediate changes. After 48 hours, all measures except for fatigue and soreness (probably the DOMS) had recovered fully.
This is where stress comes into play. Both the collective life event stress and current perceived stress impaired recovery of MIF, even after adjusting for recent exams, fitness level, fat-free mass, training experience, workload, and the degree of force reduction. In other words, chronic mental stress and acute perceived stress reduce the recovery rate after damaging exercise, and this explains – easily – some of the large variability in people with regard to post-exercise performance and soreness. With regard to jump height, only the perceived stress and not life stress was related to recovery, and neither variable affected cycling power. Stress was also significantly associated with recovery of energy, fatigue, and soreness. The energy of the participants was greatly reduced at all time-points when considering both perceived and life stress. Levels of fatigue and soreness, however, were only impacted by life stress.
There are probably a million reasons why stress impacts recovery. Just one example is that many of the inflammatory signals necessary for recovery and adaptation are dysregulated by stress. Moreover, sleep, diet, social support, and general behavior of the individual are other factors that influence stress and recovery in a complex manner. These factors may account for both the vulnerability of some people and the resilience of others when faced with stress. Overall, this study provide strong support in favor of “less is more” when stressed. If you have a lot going on in your life, that may be the perfect time to dial back your training and focus on getting things sorted out.