What is the efficiency of a subject on a treadmill who puts out work at the rate of 100 W while consuming oxygen at the rate of 2.00 L/min? (Hint: See Table 7.5.)

Efficiency is defined as the ratio of useful output by the total input.

\(\eta \% = \frac{{{\rm{Useful output}}}}{{{\rm{Total input}}}} \times 100\% \)

Here, \(\eta \) is the efficiency of the system.

The efficiency of subject on treadmill is,

\(\eta \% = \frac{{{P_w}}}{{{P_i}}} \times 100\% \)

Here,\({P_w}\)is the power at which work is done\(\left( {{P_w} = 100} \right)\), and\({P_i}\)is input power while consuming oxygen at the rate of\(2.00{\rm{ L}}/{\rm{min}}\)\(\left( {{P_i} = 700{\rm{ W}}} \right)\).

Putting all known values,

\(\begin{aligned}\eta \% &= \frac{{100{\rm{ W}}}}{{700{\rm{ W}}}} \times 100\% \\ \approx 14.3\% \end{aligned}\)

Therefore, the required efficiency of subject on treadmill is \(14.3\% \).