Lack of time is the most overused reason for not exercising. This is deep-seated on the belief that no benefit can be achieved without a serious time commitment to exercise on daily basis, exactly the excuse we are looking for to stay on the couch.
‘Myths are beliefs that people adopt because they have an air of plausibility and are at least consistent with some pieces of evidence’.
Jogging and endless treadmill wanderings are thought as the way to go to stay healthy. Personally I can’t stand either.
Really we have to exercise for so long?
The answer lies in the nature of exercise itself, which is a stimulus that acts to generate an effect, just like a drug. As suggested by Dr Doug McGuff: ‘For exercise or a medicine to produce the desired effect there has to be an optimal concentration, dosage and dosing frequency’.
In exercise terms, concentration is the intensity, dosage the duration of exercise and dosing frequency represents the number of sessions per week. These parameters should be manipulated to induce a stimulus that triggers a training adaptation.
Also like drugs there is a ‘Narrow therapeutic window’ that represents the borders of the training stimulus. This means that a stimulus that lies within the interval of the window produces a positive adaptation while on the other hand crossing the border with too high or too low a stimulus may lead to undesired results, such as lack of progress or overtraining (and training more does not mean improving more, as I often try to persuade my friend..).
In a quest to minimise exercise dosage the group led by Gibala at McMaster University investigated the effects of repeated sprint intervals of very short duration on metabolism; they designed a training program consisting in 4/6 30s ‘all out’ sprints per session with 4.5 min of rest in between to be performed 3 times a week.
They found that only 6 sessions of this protocol were sufficient to improve endurance and promote an increased activity of the master regulator of mitochondrial biogenesis PGC-1a meaning an increased skeletal muscle oxidative capacity.
These findings suggest that this minimal training program consisting of mainly anaerobic exercise produced an alteration of the metabolic state, in fact improved insulin sensitivity was also found. Similar studies found also significant decreases in blood pressure, increased resting fat oxidation and improved fitness VO2 max, probably the most comprehensive marker of health.
Could we do even less?
A recent study performed by Metcalfe et al at the University of Edinburgh paves the way for an even more minimalistic approach to training. This group designed their protocol considering that exercise benefits may be driven by the depletion of glycogen, one of the predominant energy stores in muscles utilised during exercise.
Glycogen breakdown is markedly reduced after the first 15s of the sprint and it tends to be inhibited in the following sprints. These observations suggested that the original repeated sprints protocol of Gibala et al exceeds the stimulus necessary to induce glycogen depletion, crossing the upper border of the ‘therapeutic window’. –So, exercise strain could have been reduced while maintaining potential for improving health.
Only 2 sprints per session lasting 10 to 20s for a total of 10 minutes of exercise including warm up and rest intervals performed 3 times a week were sufficient to produce an improvement in insulin resistance and VO2 max in sedentary but healthy subjects over a period of six weeks.
The other important feature of the study was the use of rate of perceived exertion (RPE), a scale used to understand exercise strain and the degree of fatigue experienced. Mean RPE found was 13, indicating an effort of ‘somewhat hard’ magnitude, equivalent of that found in prolonged cycling of intermediate intensity, suggesting that this workout is not even hard!
Could we do even fewer sessions per week? Some of the effects of exercise on metabolism are acute, they depend on the last bout of exercise, for instance the exercise effect of reducing blood triglycerides lasts only about 24 hours after your workout, meaning that you could be even an Olympian but you need to be active often if you want to keep triglycerides low.
Reducing the sessions to less than 3 a week may not guarantee these benefits throughout the whole week. Only future research can tell if we could reduce the workouts to only twice (or once?).
There is increasing evidence that minimalist training can stimulate health benefits, especially by promoting metabolic adaptations, doing so with a total amount of 30 min a week (or less?) of exercise including breaks and warm up and with a moderate physical strain. This is evidently standing out when compared to the 150 min of moderate exercise per week advocated by present health guidelines. Would be at this point reasonable to change the guidelines towards a ‘time efficient’ model that takes into account the overwhelming time-consuming commitments that characterise our present society?
Lastly, this approach to exercise would have to defeat sceptical mind-sets among both the general population and the health experts before imposing itself as the new paradigm for well-being.