It’s Wednesday and time for fitness notes again. Today we will see how the oft-talked Basal Metabolic Rate (or BMR) is affected by workouts. But before we begin, let us do a quick touch on what BMR is. BMR is the minimum amount of energy that a body requires at the state of rest and which is just sufficient for the functioning the vital organs such as heart, brain, liver, nervous system etc.
A person’s BMR is affected by a number of factors and exercise is only one of those factors. The other factors are age, weight, level of fitness, genetics, temperature, stress levels, previous meal, glands and body surface area etc. In this post, we will concern ourselves with exercises. BMR is closely related to lean body mass. If you have less lean body mass, or are endowed with more fat mass, you have a lower BMR. Alternatively, increasing the lean muscle mass (not fat), increases BMR.
Research has shown that a general increase in aerobic fitness level does not necessarily lead to an increase BMR unless it is of endurance nature. It is now proved that all endurance training (strength and cardiovascular) result in increase of Basal Metabolic Rate. This connects back to the possibility that endurance-training builds lean muscle mass and this in turn increases BMR.
Of note is the finding that though the BMR shoots up while endurance training is on and drops of gradually when we stop the session, the average BMR for the next 24 hours post exercise, remains higher than that of a non-exercise day. You can arrive at your BMR by calculating the calories you spend in the whole day including all activities – this will be your maintenance level. Alternatively, you may use the formulae BMR = 24 x Weight (lbs)/2.2.
Average BMR values are available for different races and sexes from training institutes. The maintenance level for women in the US is marked at 2000-2100 cals and that of men at 2800-2900 cals. These are averages and are susceptible to change according to the factors I mentioned at the start of the post. BMR values are of importance for not just professional athletes but also for people looking to lose weight, gain lean mass and to maintain body mass at optimum levels. You can find out what are calorific requirements will be at various levels of activity, once you know your BMR. Example: At sedentary levels, you need BMR x 1.45 calories; at medium exertion levels, you will need BMR x 1.70 calories and at heavy exertion levels, you will require BMR x 1.88 calories. However, these are only ballpark figures and cautioned must be practiced while using them.
Until next week, train safe and enjoy your weekend!