The Sun Tan Analogy

In my previous post on results versus time in training I wrote about the sun tan analogy, which I first learned from bodybuilding legend Mike Mentzer, then later from Nautilus inventor Arthur Jones. I’ve been using the sun tan analogy for years and have found it to be one of the most effective ways to explain several important concepts to new trainees, including the difference between stimulating and producing results, the relationship between intensity, volume and frequency of training, and individual variability in response to exercise. Although not specifically mentioned, the first part of the analogy is a basic explanation of general adaptation syndrome (GAS), the body’s response to stress, and why brief and infrequent training is necessary to keep the body in the reaction stage of GAS (adapting to exercise) and out of the exhaustion stage (overtraining).

The second part of the analogy, which was not included in the previous post, explains how individuals vary in their response to exercise and how the volume and frequency of training must be adapted to the individual.

I am posting this here for trainees and personal trainers who may not have read or heard the analogy before to provide what I’ve found to be a very effective tool for explaining these principles.

The Sun Tan Analogy Part 1: Stimulating versus Producing Improvements in Fitness, and Intensity, Volume and Frequency

Exercise is a type of stress we apply to the body to stimulate an adaptive response. The key word being “stimulate”. Exercise does not directly produce any improvements in the body, it stimulates the body to produce those improvements as an adaptive response to enable it to better handle the same stress in the future. In many ways, it is like getting a sun tan.

Exposure to sunlight does not directly produce a tan. The ultraviolet radiation in sunlight stimulates melanocytes in the skin to produce more melanin as a protective mechanism, darkening the skin. The brighter the sun, the more intense the radiation, the stronger the stimulus. The same situation occurs with exercise or any other stress – the more intense the stress the greater the stimulus for adaptation. If the sky is cloudy you can lay out all day and not stimulate any noticeable tanning because the intensity of ultraviolet radiation would be too low, but if the sun is high and the sky is clear you only have to lay out a little while to stimulate a tan. The same thing happens with exercise. If the level of effort is low you can do a large amount of exercise but not stimulate much in the way of improvements, but if the level of effort is very high very little is required for good results.

If a stress is intense enough to stimulate a significant adaptive response though, there will be a limit to how much the body can handle within some period of time. Up to a point, intense sun exposure will stimulate a tan, beyond that it starts to damage the skin, causing a burn. Up to a point intense exercise will stimulate improvements in strength, metabolic and cardiovascular conditioning and other aspects of fitness, but beyond some point the demands of the workout exceed what the body is able to recover from and adapt to and eventually can cause a loss of strength and conditioning, a situation called “overtraining”.

If you lay out to tan or use a tanning bed, when you’ve finished you don’t go back out or back to the bed and do it again five minutes later. The body needs time to recover before being exposed to the same stress again or the process of recovery and adaptation is interrupted and you risk damage. The same is true of exercise. After a workout your body requires time to recover from the effects of the workout and produce the improvements the workout stimulated. Although the amount varies between individuals, most people underestimate how much time they need for recovery between workouts.

If done properly the most exercise anyone requires for best results is around three half-hour workouts per week and many people get better results training only twice weekly or less. Longer or more frequent training will not produce better results and eventually leads to plateaus and overtraining.

The Sun Tan Analogy Part 2: Individual Variability in Response to Exercise

The volume and frequency of exercise that works best varies between people due to differences in genetics and other factors in the same way that the duration and frequency of sun exposure required for tanning varies between people with different complexions. Someone with darker skin can tolerate a longer duration of intense sun exposure and do so more frequently without burning than someone with lighter skin. Some people can do more exercise, more often without overtraining, and some can only handle very short durations and require a longer time in between to recover and adapt.

While skin color is obvious, the optimal volume and frequency of exercise for an individual is not. The only way to determine it is through experimentation. Keeping accurate records of exercise performance and paying attention to relevant variables like nutrition, sleep and other physical activities and stresses and making adjustments to the workouts and training schedule based on individual response.

When in doubt about the optimal volume and frequency of training, it is best to err on the low side. Erring low may result in a slightly lower rate of progress if the trainee recovers quickly enough to train more frequently, but would still be effective, while erring high can lead to overtraining and a stall in progress altogether.

The appropriate workout frequency depends on both the individual’s unique response to exercise and their training goals.

Optimal versus Effective

Optimal versus effective volume and frequency is an important consideration for personal trainers for financial reasons. Unless a client is a competitive athlete, in which case successful competition demands the best and fastest possible results from training, a training frequency that is simply effective will allow most clients to achieve their goals while making training more affordable for them. The effectiveness of an exercise program is proportional to the intensity of the workouts rather than how long or often they are performed, and when increasing either the volume or frequency of exercise one quickly hits a point of diminishing returns.

When training with a sufficiently high level of effort, increasing training frequency from two to three weekly workouts – a fifty percent greater time and financial investment from the client – would not result in fifty percent better results, and can even be counterproductive if the client requires more recovery time. Research and a massive amount of empirical evidence also shows if training intensity is high enough working out only once weekly can produce results comparable to twice a week.

While this would not be optimal for someone who is able to recover and adapt in a shorter time frame, it would still be far more effective than mainstream personal training programs which tend to involve several hundred percent greater weekly time investment and greater cost. If you’re in doubt, consider there are independent personal trainers and high intensity training studios thriving throughout the United States and Canada who have built their business on once-a-week training.

If you’re a trainer you may be thinking this is insane, since if you are currently training clients two or three times weekly cutting your clients’ workout frequency back by a third to a half would result in a huge loss of income. This might be the case initially, but in the long run it would work to your advantage, because it more than doubles the target market for your services. By reducing the monthly or yearly training cost by one third to one half you increase the number of people in your area who can afford you by far more than that. For studio owners considering additional locations, this also means a viable business model in areas with a lower average household income than would be required for studios using more typical personal training frequencies.

Keep in mind what you are selling is results, not your time, and by giving your clients far better results than your competition in an even smaller fraction of the time you are providing them with more than just a much greater return on their investment – you’re freeing up more time for them to enjoy their improved fitness and appearance doing other things.

My recommendation, based on what I’ve been doing with my own personal training clients for nearly two decades, is to start with twice-weekly, full-body workouts and adjust from there based on the client’s goals and their response to exercise. Encourage nutrition, sleep and stress management habits conducive to recovery from and adaptation to exercise, and don’t be afraid to suggest a brief layoff from training when required or reduce training frequency if the client needs more recovery between workouts.

1. Braith, R., J. Graves, M. Pollock, S. Leggett, D. Carpenter and A. Colvin. Comparison of two versus three days per week of variable resistance training during 10 and 18 week programs. International Journal of Sports Medicine 10: 450-454, 1989.

2. Feigenbaum, M., and M. Pollock. Prescription of resistance training for health and disease. Medicine and Science in Sport and Exercise 31 (1): 38-45, 1999.