FItness Physics

As a card-carrying seven-day-a-week gym rat there is one thing of which I am certain

What propels me through the gym are the smoothly coordinated actions of my glutes, my quadriceps, and my hamstrings and that is how I have able to confidently saunter through the gym Of this I am unequivocally positive! You are right in the sense that the mechanical energy is being generated is coming from your legs your muscles are turning chemical energy of the carbs and the little fat and the sugars into mechanical energy but the force the thing that's changing your motion the thing that's propelling your feet forward is the frictional force between your feet and the ground you do a lot of water aerobics right that's true if you're in the water and you're not touching the bottom and you try and walk don't go anywhere you did the Fred Flintstone thing but you don't know anywhere think about like trying to walk on ice very difficult and what's different about ice resistance is futile actually non-existent your muscles and your foot are pushing on the ice but there's nothing pushing back on you what your muscles are doing is bringing the non plant foot forward how fast must my non planted foot ahh a typical walking speed is something like 3 miles an hour right so that's a night of relatively comfortable brisk walk right for somebody in reasonably good shape let's call it a meter per second you're moving forward your hips your of your waist is moving forward at a meter per second the foot that's planted isn't going anywhere that plant foot spends half of its time at zero velocity well foot that's coming forward has to catch up pass you pass your hips and then get in front of you it's got to go forward at 2 meters per second just to catch up there isn't could look a whole upper part of my body is still moving like it's just – Newton's laws again right your body's moving forward if you suddenly stop your feet you're gonna end up doing a faceplant into something but the speed equation of that back leg changes when you are running it does yeah what's the difference between walking and running is the question when you're walking one foot is always on the ground but when you're running both feet spend some time in simultaneous flight So then that plant foot the foot that that you are pushing off on she spends less than half of its time stationary so when you are running that back leg does not have to move forward as fast relative all your body your body right when you were walking these long-distance walkers they do that thing they're at the maximum overturn rate to keep a foot planted their back leg when they pick that up it is moving forward very quick lawn average throughout the motion twice as fast as the your body and these are the things I think about well while I'm working out, right? I appreciate it, very much and now our fellow gym rats get to think about the physics of walking and running as well Dr Nichols Gross teaches physics at the esteemed Boston University see out there on the track brother

Thank you so much, Aaron yeah Or in the gym Yeah