Units of Measure Continued

Power - depends on the total amount of time you have to complete the work

  • everyone can produce huge amounts of work if given enough time

Power = work / time

  • Power (W) = Work (J)/Time (s)

Why is power important?

  • It provides the rate at which exercise is performed, tell us the intensity

Common terms to use for Power

  • Watt - 1 W = 6.12 kpm

  • Horsepower - 1 hp = 745.7 W or 10.69 kcal

  • Kilopond-meter - 1kmp = 0.163 W

Find power if performing 20,000 J of work in 60 sec

What’s required to calculate how much work and power we produce?

  • Work

    • we need a force produced

    • Need a distance, how much distanced we produced

  • Power

    • Need to know the work produced and how long it took us to do the work

Measurement of work and power

  • Ergometry

    • Measures work output

  • Ergometer

    • Device used to measure work

    • Bench step ergometer

    • Cycle ergometer

    • Arm ergometer

    • Treadmill

Bench step-calculation of work and power example:

  • 70 kg subject, 0.3 m step, 30 steps/min for 10 min

    1. Calculate the force produced by the subject

    2. Determine distance traveled

    3. Calculate total work produced

    4. Convert this to proper units

    5. Calculate the amount of power this subject produced

How many kcals per hour was this activity? - 1 watt =-0.0569 BTUs per minute 0.86kcal per hour

Cycle Ergometer-calculation of work and power - stationary cycle that allows accurate measurement of work performed

  • 1.5 kp resistance, 6 m(rev^-1), 60 rev(min) for 10 min

    Convert to kcal? - 4186 J/kcal

MET:

  • resting metabolic rate

    • Taken as 3.5 mL kg min^-1

    • Energy expenditure of physical activities expressed in terms of multiple of MET unit

  • you need 500 MET minutes per week for optimal cardiovascular health

  • That is about 150 minutes of moderate intensity exercise per week

    • Biking 3 times a week at 13mph for 15 minutes & walking at an incline for 15 minutes 2 times a week will get you to 500 MET per week requirement

Estimation of Energy Expenditure:

  • VO2 = 0.1 mL(kg)(min) x speed + 3.5 mL(kg)(min) *WALKING

  • VO2 = 0.2 mL(kg)(min) x speed + 3.5 mL(kg)(min) *RUNNING

What is the O2 cost of walking at 80 m/min:

  • how many kcals per minute will they be burning with a 60kg person

  • How many MET of activity is walking at this speed

What is the oxygen cost (O2) of a person running at 6mph (161 m/min):

Running Economy:

  • oxygen cost (energy expenditure) of running at a specific speed

  • Lower VO2 at the same speed indicates better running economy

Muscle Fiber Type:

  • slow muscle fibers are more efficient in using ATP compared to fast (type eight fibers)

Individual differences in running economy:

  • elite runners are more efficient to non-runners