My psychiatrist told me that depression does have an effect not only on motivation, but also on physical fitness, unrelated to training or sedentary behavior.

My psychiatrist told me that depression does have an effect not only on motivation, but also on physical fitness, unrelated to training or sedentary behavior. Apparently it's related to how the nervous system is affected by depression, which in turn changes how your body reacts to physical exercise. This explain why despite doing physical activity, it became immensely more difficult to go running when depression came back. This is really important to remember to do physical activity but to go slowly and not expect to be fast or to improve. Depression suits reduce physical fitness, but not just because you stay inside.