MORE ABOUT HOW MUCH EXERCISE

My flow of thought has been interrupted by the dreaded virus – My last non-Covid blog went out on 14th March and spoke about how much exercise we need to take for the sake of our health. Mainly it was about the exercise recommendations of the Department of Health. I mentioned that different desired outcomes  demand different levels of effort.  Here are further approaches to deciding appropriate exercise programmes.

When Professor Morris described the incidence of heart attacks in bus drivers and bus conductors he believed that there was a threshold for achieving a fall in the rate of heart attacks and in reduction of mortality. This might not be entirely true but the threshold which he described outlines a very useful level of exercise for everyone:

How often, how hard, how long?

The government advice is good but here is another way of looking the amount of exercise which will do you good. This regime has been shown to increase aerobic fitness – more of which later.

Frequency: You start to benefit from exercising once a week and the benefits increase up to three or four times weekly and, though still increasing,  start to flatten off thereafter. Beyond three or four times weekly the chance of sustaining muscle or joint problems (strains and sprains) increases.

Intensity: This is best measured by the effect on your heart (pulse) rate (HR). The easiest way of checking this is to wear a device which measures it for you. Alternatively feel the pulse in your wrist or neck (don’t push to hard!) and count it  – either for six seconds and multiply by ten, or for 15 seconds and multiply by four. At rest your HR should be between 60 and 80, and the fitter you are the lower it will be. If you are very fit it may even be in the low 50s. Your maximum HR is approximately 220 minus your age – a useful if not always accurate rule of thumb.
For increasing fitness the ideal exercise HR will be between 70% and 85% of the maximum.  70% maximum HR is about 170 minus your age and 85% is about 195 minus your age. A sixty year old should therefore exercise to a heart rate of between 110 to 135. As a rough guide this is the exercise intensity which should make you moderately short of breath. You can just about talk but not sing. Pushing yourself harder is perfectly safe but the return for the increased effort becomes less the harder you push. If you have heart disease, excessive exertion can bring on cardiac rhythm disorders.
NB Some prescribed medications, particularly beta-blockers (ie bisoprolol, propranolol) lower your heart rate so that these figures are not applicable.

Duration: The shape of the response curve applies also to the duration of each exercise session. The greatest relative benefit is from doing short bursts but this response starts to flatten off at between about 30 and 60 minutes. As with frequency, longer bouts of exercise carry a greater chance of strains and sprains while only slightly increasing fitness further.

These guidelines apply to ordinary folk wanting to keep themselves in good shape. Greater effort does bring greater increases in fitness but the return for your effort gets less. Such effort is necessary for those involved in competitive sports – but does mean that such sporting types spend quite a lot time nursing their injuries. Such is the price of fame.

What about pedometers?

Another aid to increasing activity is the pedometer, available as wearable technology or on a phone app. It is generally recommended that 10,000 steps per day should the the target – but as with all forms of exercise, any number is better than none. The precise figure of 10,000 has little science to back it up but it is a convenient round number and there is evidence that it is more or less in the right ball park. Pedometers only measure total numbers of steps and say nothing about frequency, intensity or duration. 10,000 strides equals about 5.7 miles which would represent a good daily dose of exercise. In practice most of the steps counted are much shorter – just pottering about. 10,000 steps for most people represent less than two miles rather slowly.

Some devices and some apps give more information. The NHS recommended app is Active 10 which measures not only paces taken but also walking speed. It records the number of minutes of brisk walking and recommends a starting level of 10 minutes a day, building up to three ten minute bouts of brisk walking daily.

What is the effect?

The greatest benefit of using such regimes to get fitter is the reduction in a vast array of diseases of later life (heart disease, high blood pressure, diabetes, osteoporosis, loss of balance, etc etc)  and ultimately less frailty leading to a longer and more productive life. Probably different levels of exercise have different effects in each of these but optimum levels have yet to be worked out. For most conditions the more you do the greater the effect.

One set of conditions which responds poorly to this level of exercise is over-weight and obesity. To achieve weight loss the level of exercise required is double or more the standard recommended level. The interaction between daily activity, exercise training, diet and weight is fascinating and I will be writing about this in a future blog.

PS

Walking and running.

May I recommend an article in this month’s New Scientist – Gotta Run^1. The author analyses the benefits of walking and running as aids to physical fitness and good health and compares them. He emphasises that the greatest gains come from a change from doing nothing to doing something. “More running is better, though with diminishing returns”. He also quotes a paper which calculated the increase in life expectancy from running.  For every hour run, lifespan increases by seven hours! That means that  someone running two miles a week from the age of 44 to 80 gains nearly three years. Walking can bring similar benefits but takes much longer. A five minute run generates the same benefits as a 15 minute walk.

1. Haake S. Gotta run? New Scientist 2020, 245:34-38