The body is almost identical to any motoring vehicle with an engine, meaning that it has to be always in use and if it is left in idle for too long there will be a delay in responsiveness; when it is finally used it has to be warmed up so that the parts are moving in unison . This is evident when you haven’t worked out in a while or had a consistent regime in regards to working out (ie waking up for breakfast then attending gym or working out at a specific time) when you have this unison, everything works well and your body timing and responsiveness works in harmony, there is no delay, but if you disconnect from this unison you will notice that at first you feel lazy or a lack of responsivenessuntil you begin again (restart), then once you start to reconnect to this order of things. Your mind will feel clearer, thoughts are more productive and positive and you can work out for longer. You are taught this erroneous notion that the heart is the pump of the body, when in fact the lungs are the pump of the body and the heart is the valve hence why the heart is almost identical to the valves on a car engine. So to fill this pump, oxygen is needed so it’s best to do aerobic exercises to help the responsiveness, similar to a car if there is a blocked valve in the engine the car will not respond correctly till the blockage is clear. Try this yourself when you feel stressed or lazy do an experiment with yourself work out at the time of laziness then record your results on how you felt after the workout,and see if your body responds better after. You may be surprised with the results.