Physical activity improved thinking, creativity, and quality of life and also countered key health risks, including cardiovascular and neurological diseases, he said.
Exercise was versatile and ''highly accessible'' but should not be simply ''put in a box'' and viewed only as medicine.
But Prof Cotter, of the Otago School of Physical Education, Sport and Exercise Sciences, yesterday gave an inaugural professorial lecture on ''Exploring exercise, the environment, and their extremes'', and also commented in an interview.
Exercise and fitness were ''immensely complex'' and were also often misunderstood or insufficiently understood.
The experience of walking or undertaking other exercise at the beach or in other beautiful countryside near Dunedin also offered wider, holistic benefits, including spiritual insights, he said.
''Natural environments provide rich opportunities for human development.''
People benefited from being physically active in the natural environment, and given rapidly rising levels of inactivity among New Zealand adults, access to the countryside was becoming ''a fitness issue''.
Declining physical fitness potentially meant less access to natural environments, and could also mean declining awareness of them, and reduced advocacy to protect them.
Prof Cotter researches how stressors within exercise and the environment affect people's physiological systems and functional abilities.
Exercise was a ''uniquely complex stress'' and generated heat.
Human heat defences were ''uniquely powerful, elaborate and complex''.
Exercise and fitness were ''important, but not at the expense of the environment'', he said.
