Exercise | Power Generated

We use our Body-Solid home gym regularly. My workout takes about 20 minutes with pauses between routines. Today. I didn’t pause. Workout time was 15 minutes, or 900 seconds.


A principle of physics I taught about involved work, energy, and power. I wondered how much work was done lifting the weights during my workout. Each routine raised the weight different amounts. Units used are Newtons of force and meters of distance. 1 N-m = 1 Joule of work.

Work done = Newtons x distance x number of reps


Total work done was the sum of the separate routines equal to 20,900 Joules.

Average power generated, or work per second, equals 23 Joules/sec, or 23 Watts.

Metabolic Equivalent

If I just sit around and do nothing, my body utilizes energy at a rate of about 81 Joules/sec, or 81 Watts. It is calculated from the Metabolic Equivalent expression of 1.162 Watts/kg. I multiplied my 70 kg x 1.162 Watts/kg to get 81 Watts.

Other physical activities are scaled with reference to this figure. For example, earlier I went for a walk at a brisk pace of 3.4 mph for about 30 minutes. According to the tables, energy was utilized by my body at a rate 3.6 times the metabolic equivalent, or 81 x 3.6 = 292 Watts. Bicycle racers can generate 500 Watts for hours at a time. If a level of 746 Watts is reached, it is also known as one horsepower.

You can look up many activities at the Compendium of Physical Activites. They include things like bicycling, dancing, sexual activity, lawn mowing, etc. Each is rated with a Metabolic Equivalent score. Take your body mass in kg x 1.162 x the score in the activity.

Melanie said “Be sure to provide a link to your post about mowing the lawn.” Thank you, dear.


17 thoughts on “Exercise | Power Generated

  1. I learned them as MET Levels in Cardiac Rehabilitation, the Metabolic Equivalent of Task, or MET level, as the approximate amount of energy a person uses during physical activity. They were used as a reference point during cardiac rehabilitation. Patients who have had a heart attack or who have undergone open heart surgery are assisted to gradually return to normal activity levels, using MET levels as a guide to insure that activity does not exceed what the patient’s heart can tolerate.

    Then we were given these guidelines:

    Class Patient Symptoms Approximate MET Level Tolerated

    I No limitations. Patients do not experience heart palpitations, shortness of breath, or extreme fatigue during normal physical activity. 4.5 and over

    II Slight limitations of physical activity. Patients are comfortable at rest. Ordinary physical activity results in palpitations, shortness of breath, or fatigue. Up to 4.5

    III Significant limitations of physical activity. Patients are comfortable at rest. Light to moderate activity causes palpitations, shortness of breath and fatigue. Up to 3.0

    IV Unable to tolerate physical activity. Patients experience palpitations, shortness of breath and fatigue even at rest. Physical activity increases the severity of symptoms. Up to 1.5

    For O.T. this would be assessed as follows:

    Stage 1
    1.0 – 1.4 SITTING Self feeding, bed mobility, reading, transfers

    Stage 2
    1.4 – 2.0 SITTING Self bathing, grooming/dressing, slow pace mobility as tolerated, crafts

    Stage 3
    2.0 – 3.0 SITTING Showering warm water, ironing, homemaking tasks with brief standing periods, piano, typing

    Stage 4
    3.0 – 3.5 STANDING BADL warm water, kitchen and homemaking tasks whilst conserving energy, unlimited distance walking, cycling 5mph flat, light gardening, golf putting, canoeing

    Stage 5
    3.5 – 4.0 STANDING Washing clothes/dishes, ironing, making beds, cycling 8mph flat, slow swimming, golf using cart

    Stage 6
    4.0+ STANDING Showering in hot water, mopping/raking, stripping and making beds, cycling 10mph flat, swimming, volleyball, badminton

    So stage 6 would mean they achieved their goals.

    Liked by 1 person

    • The first time I read about estimates of the human energy needs came from a report centuries ago the the persons in charge of feeding the French army. It must have been after the 1790s as they were using metric values. They determined the base level of a human was about 100 Watts.

      Your information is very interesting. Thank you.


  2. All I’m going to say is this…. you totally geeked that out! However, I do see the nice lines of the machine. They don’t come in pink or purple? No lace? It’s kind of ….(with nose turned up) clinical isn’t it? I would have needed…. lol….polka dots on that bad boy or something…..lol
    I’d get the most use out of a machine that let me do a rowing type motion for my shoulders. I’ve been thinking about that for a little bit now. I won’t break down Newtons of force but I would keep progress reports…on pink paper with polka dots and lace trim. 🙂


    Liked by 2 people

  3. Nice machine! Very interesting scientific study. I get the feeling you don’t do anything without thinking. The next time I’m chopping wood I’m going to think this is way harder than sexual activity (but not nearly as fun), but not nearly as difficult as cycling (however, much more enjoyable). My mind will probably wonder. Wonderful post Jim. There has got to be some calories burned just putting up with the cold weather. Bob

    Liked by 2 people

  4. I think the closest most Americans have come to newtons is eating a certain fig bar.

    In New Zealand last year I was surprised to find labels on food containers listing the number of kilojoules rather than calories per serving.

    Liked by 1 person

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