There are many benefits to high intensity exercise, but there are also situations in which low intensity can be the best way to go. Let’s use as a prime example the case of the client whose main goal is losing fat.
Often, the client starts off by being most efficient at using carbohydrates for energy during exercise and most inefficient at mobilizing and using stored fat. That means the person’s body responds to an energy requirement that rises quickly above a resting metabolic rate by turning first to carbohydrate metabolism. As a result, aerobic exercise design should emphasize fat metabolism while de-emphasizing glucose metabolism. A common exercise prescription that fits that bill is one that calls for low intensity with relatively long duration.
What is ‘Low’?
In terms of heart rate, the response should be a slow, gradual progression in rate over several minutes until the client’s exercise heart rate climbs to 60%-70% based on goal-oriented application of Karvonen Formula. There should be a noticeable, progressive in the client’s respiration, as well.
Using the “talk test”, the client’s respirations should not prevent him or her from being able to speak comfortably within the 60%-70% intensity range. Using the Borg – or Rating of Perceive Exertion – scale, the client should try to remain at 11 (fairly light), with a range of plus or minus one level to make sure the body’s capacity to furnish sufficient fat for conversion to energy is not exceeded and at the same time, that glycogen conversion and use is minimized.
When establishing an intensity range, it’s important to take into account the individual’s age, cardiorespiratory function, and level of aerobic conditioning. Over time, the client’s improving cardiorespiratory function should allow for exercise intensity to be progressed as tolerated.
Typical recommendations for aerobic activity range in duration from 15 minutes to an hour for each session. For the fat reduction client, the upper end of that range could be extended if exercise intensity kept at the lower end of a prescribe heart range intensity range.
This same recommendation holds for strength athletes and older clients who are interested in fat reduction and the relatively modest cardiorespiratory benefits this type of activity offers. Another advantage to performing lower intensity in this case is that can be performed both more frequently and for longer durations than more intense aerobic activity. The main benefit here is to the cardiorespiratory system. That means, among other things, that low intensity exercise can be done on a daily basis by most clients.
Some recommended forms of exercise for low level intensity includes walking, cycling, stationary cycling, even min-trampoline bouncing. Intensity in these exercises is easy to control and can be progressed easily. In addition, such exercises are comparatively low impact and don’t require learning many (if any) new skills.
In review, points to remember for low level and aerobic activity for the fat reduction client are that they should be:
-Low in intensity (in the 60%-70% range)
-High in frequency
-Long in duration
As can be seen, exercise selection should be directed toward activities that can be performed with low impact and low intensity for relatively long periods of time, that require minimal coordination, and that are rhythmic in nature. Fortunately, these exercises can be practiced and enjoyed by a broad range of clients to add variety and interest to any program.
1. The National Federation of Professional Trainers. Personal Trainer Certification Manual. 5th Ed. Lafayette, IN: NFPT, 2008.