Saturday, 18th January 2020



There are two broad categories of exercise. Dynamic or isotonic exercise is that which uses the regular, purposeful movement of joints and large muscle groups, particularly their Type I fibres. Isometric exercise, on the other hand, involves static contraction of muscles with little or no joint movement, predominantly involving Type II fibres. Other descriptors of exercise category include aerobic (using oxygen) and anaerobic (not needing oxygen). Most activities involve a combination of these factors and classification is typically expressed as the dominant characteristics of the particular exercise.

 Aerobic/Dynamic Exercise

Dynamic or aerobic exercise includes such sports as running, cycling, swimming and aerobic dance. They involve much movement and little strength and can be continued for long periods and are sometimes referred to as “cardiovascular” workouts. They are dependent on a good supply of oxygen which fuels the energy produced by the breakdown of glycogen stored in the muscle. Such exercise, performed at the right level, can be continued as long as there is a sufficient supply of carbohydrate (sugar) in the form of glycogen. If the duration and intensity of the exercise is sufficient to deplete the stored glycogen faster than it can be replenished, muscle fatigue sets in and the exercise must be greatly reduced or stopped. This is the experience of the marathon runner who “hits the wall”. The effort of aerobic exercise is mainly performed by Type I, or slow twitch, muscle fibres. Most of the clinical benefits of exercise in preventing and treating chronic diseases have been demonstrated for aerobic exercise and it is this form of exercise which is the main subject of my Blogs.

Anaerobic/Isometric Exercise

Anaerobic or isometric exercise involves much strength but little movement. More mature readers will remember the once well-known Charles Atlas muscle building techniques. These were pure isometrics, involving one muscle group straining against another without movement – a form of exertion designed to build up muscle bulk. The muscle fibres used are the Type II, or fast twitch, fibres. They do not use oxygen and they quickly fatigue. Most so called anaerobic exercises do involve some movement but make much more use of strength. Examples are weight lifting and sprinting. In the clinical context, isometric exercise is much used by physiotherapists in the treatment of joint injuries and after orthopaedic surgery. Muscle strengthening is also very important in the treatment of frailty and balance problems in old age.

Mixed Exercise

Nearly all exercise involves a mixture of aerobic and isometric effort though one or the other usually predominates. Most gym fitness training programmes use a mixture and the recommendations of the Department of Health were updated in 2005 to include “muscle-strengthening activities on 2 or more days a week work all muscle groups (legs, hips, back, abdomen, chest, shoulders and arms)”

In practice
We humans are not all born with the same balance of slow twitch and fast twitch muscle fibres. Although the average is around a 50:50 balance, some people inherit a pattern in which one type predominates over the other by anything up to about 70:30 split. Those born with a predominance of slow twitch fibres will make better endurance athletes while those otherwise endowed make better sprinters. Specialist training can change the balance somewhat but a born marathon runner will never make a champion sprinter.

In the gymnasium you will find a number of exercise types on offer. These are some examples:
1. “Cardiovascular” – this includes mainly aerobic exercise such as cycling on an ergometer, walking or running on a treadmill, skipping, aerobic dance and any other exercise designed to raise the heart rate and  make you  thoroughly short of breath.
2. “Bums and tums” – aimed mainly at young to middle aged women concerned about their body image, this consists of a mixture of aerobic and isometric exercise concentrating on the abdomen, buttocks and thighs. Crunches, squats and jogging may be included.
3. “Pilates” – an exercise system involving a mixture of mental concentration, economy of movement, building up core strength and breathing control. This may use free standing exercise or weights and pulleys.
4. “Body balance” – uses a mixture of yoga, tai-chi and Pilates to improve core strength, relax the mind and enhance flexibility.
5. “Spinning” – is group cycling under the direction of an instructor who changes the load and speed through the session – mainly aerobic.
6. “Aquarobics” – exercise in the swimming pool which uses the resistance of the water to exercise different muscle groups. This is particularly suitable for those with lower limb problems need the support provided by the flotation environment and who would be unable to exercise without support.
7. “Calisthenics” – a variety of body movements, often rhythmical, generally without using equipment or apparatus, thus in all essence body-weight training. They are intended to increase body strength, body fitness, and flexibility, through movements such as pulling or pushing oneself up, bending, jumping, or swinging, using only one’s body weight for resistance.
8. “Zumba” – a form of aerobic dance with varying rhythms and intensity which can be adapted to all age groups.
9. “Boxercise” – an exercise class based on the training concepts which boxers use to keep fit. Classes can take a variety of formats but a typical one may involve shadow-boxing, skipping, hitting pads, kicking punch bags, press-ups, shuttle-runs and sit-ups.
10. Etc, etc.

The possible combinations of exercise are infinite and the effects of one form compared with another depend on the balance of aerobic, isometric and flexibility exercises. They are all good so if you want to use the gym and don’t find it too boring just choose that or those which you will enjoy. There is no greater disincentive to sticking with a programme than not wanting to be there! And there is no evidence that one sort of exercise class is any better or worse than any other – whatever the individual adherents may say.

My personal preference is for competitive sports or outdoor exercise. Team sports have the disadvantage of the need to find a number of like minded individuals to join you. You probably need to belong to a specific sports club. Running, swimming and cycling can be performed in groups or on your own and have the great advantage of the convenience of being fitted in with whatever else is going on your life. Just choose the exercise(s) which suit you best and which you enjoy enough to want to continue in the long-term. If it gets you moving and out of breathe it is doing the business.


This weeks exercise news is that kids playing football are no longer to be allowed to head the ball (see my Blog of  07/12/19  which reports the increased risk of dementia and other neurological problems in ex-professional footballers). Is this sensible? I wonder about the evidence for the vulnerability of the young brain versus the older brain? And the relative risk of Saturday afternoon amateurs versus professional players who presumably practice their heading skills regularly and intensively. It strikes me that there is only evidence to support the banning of heading  for professional footballers. Is that likely to happen?




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