Question 1

What is a metabolic equivalent and what are its limitations?

Accepted Answer

1 MET is the energy cost of sitting quietly, conventionally an oxygen uptake of about 3.5 ml/kg/min. Light activity is under 3 METs, moderate 3 to under 6 and vigorous 6 or more. METs assume a reference adult, use total body mass regardless of composition, tend to overestimate resting expenditure and ignore age, fitness and disease.

Question 2

Which rating of perceived exertion scale should I use?

Accepted Answer

Either, provided you say which. The original Borg scale runs from 6 to 20, with moderate activity at 12 to 13. The modified category-ratio scale runs from 0 to 10, with moderate at 5 to 6. Mixing them up gives very different prescriptions, so state the scale in the notes.

Question 3

Why is 220 minus age unreliable for prescribing intensity?

Accepted Answer

It carries wide individual error even in health. Beta blockade, autonomic neuropathy, atrial fibrillation and some paced rhythms make generic heart rate zones unreliable, and they also fit poorly in children and in pregnancy. In these situations prescribe and monitor by perceived exertion or the talk test.

Question 4

Is interval training better than continuous moderate training?

Accepted Answer

There is no clear winner. Some work-matched studies show a stronger mitochondrial stimulus, and some low-volume protocols improve maximal oxygen uptake in less exercise time. Total session time, tolerability and adherence erode that advantage, and the evidence is less certain in frailty, multimorbidity and unsupervised practice.

Exercise Intensity and Dosing

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