“…A linearly reduced risk of depression by physical activity physical activity moderates depressive symptoms-disabilityhas been observed (Strawbridge et al, 2002), the effect pertaining to at least a moderate amount of exercise or recreational activity (Farmer et al, 1988;Camacho et al, 1991). Clinical trials involving older adults lend support to the efficacy of exercise training in reducing depressive symptoms (Mather et al, 2002;Barbour and Blumenthal, 2005). Various hypotheses have been raised on physical activity's mental health benefit, including increased self-efficacy, mastery, social interaction, and brain synaptic aminergic transmissions (Paluska and Schwenk, 2000).…”