closeup of an athletic man breathing hard during an intense fartlek running session. aerobic exercise and cardio outdoors

pace aerobic hiit sprint highintensity speed fitness running pacing race fast fartlek endurance stamina intense run jog jogger runner athlete cardio cardiovascular exercise workout marathon determination physical trail summer interval male man asian southeast filipino indonesian malaysian chinese sportswear serious focused concentration fit lifestyle athletic health healthy working exhale closeup breathing hard session outdoors sports muscle person clothing boy spring model sunglasses limb arm athletics session outdoors