Perhaps the placebo effect so often talked about is actually psychosomatic medicine. A research article entitled Chronic Psychological Stress Impairs Recovery of Muscular Function and Somatic Sensations points to this.
There are physiological *AND* psychological costs to training. Stress is a disruption from the homeostatic state, regardless of the type of stimulus. We break ourselves down with the plan, and goal, of building ourselves back up––stronger than before.
However, I often see athletes and coaches emphasise the first part of the improvement equation:
Stress + Rest = Progress
Rest is where ALL the adaptations, the advancements, occur. Without recovery progress won’t happen, at least not to the desired, or full, capacity. Our culture prioritises active engagement in something, and ‘stresses’ an importance of _doing_ something. But rest, too, requires active, committed engagement, and is equally important (sometimes more important if the system has undergone a very acute or long-term chronic stress).
Science is often unable to detect measurable affect from things that we anecdotally know to be helpful and pleasurable, and thus qualify any beneficial change as a placebo response. What I hear is, “it’s just in your mind.” Personally, there is no ‘just’. By supporting the mental stress via relaxation, massage, rolling, stretching, yoga asanas (which is only 1 of 8 Limbs of Yoga), community, meditation, time in nature, healthy eating, etc. we connect to ourselves, others, and the energy that binds and flows through all living things. Yes, this sounds like the Jedi Force, but the point is that higher levels of stress result in lower recovery curves. Taking time and space for recovery is important.