I think that the limitation here is aerobic respiration. Your heart and lungs can only get so much oxygen to your muscles. For a very quick burst, you can use the reserves in the blood in your legs and you can also dip into anaerobic respiration (lactic acid generation), but this cannot be sustained for more than a few seconds. So, you can sprint up a couple of flights of stairs (which for a 100 kg person going up a 10 meter flight of stairs in 5 seconds is about 2kW or 3 Horsepower), but you cannot sprint up 10 flights of stairs. There may also be a thermal dissipation problem in your leg muscles. I wonder if an ultra-fit marathon runner or cyclist could sustain >500 Watts for minutes? Sean On Fri, Apr 15, 2011 at 10:18 AM, RussellMc wrote: >> > =A0This works well, provided that your supply can tolerate the high >> > current/no current approximation to a constant value resistor. >> > I used this for an exercise cycle load with dissipation varying >> > between 0 - 500 Watts depending on load and speed. > >> I'd break that bicycle. I think I sustained a kilowatt of power output a= t >> one point for a short time with my legs. > > No. > Getting more than 500 Watts out of it was a challenge. > Given enough speed you could do so as it asymptoted to about constant > torque, but I think 1000 Watts was probably beyond it. > > I could do 500 Watts plus for maybe 10 seconds, after which I and my > legs turn to Jelly and I can't do anything much for a while. > 100 Watts continuously is annoyingly heavy but doable. > 50 Watts a really fit person can do all day. > To fly the English Channel (Gossamer Condor / Albatross) you need to > produce a horsepower plus continuously. > > The annoying ones were the kids who set the load to zero and then > pedalled at astoundingly high speeds. Thgis would push the bus voltage > over the ;level sustainable by my load FET. I added software to load > the system down if people truied this. It worked. > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 R > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .