CYCLING PERFORMANCE TIPS

Basal Metabolic Rate

You can estimate your BMR with the following formula:

• BMR (men) in Cal/day = 10.2 times weight in kilograms + 879
• BMR (women) in Cal/day = 7.18 times body weight in kg + 795

These are replacement Calories and already take into account the inefficiency of digestion, transformation to ATP, etc. discussed elsewhere.

The BMR is about 5 to 10% lower in women than in men of a similar weight. This does not reflect a sex difference in the metabolic rate of similar tissues, but is a reflection of the fact that women generally have more body fat than men of similar weight, and muscle tissue, being more metabolically active than fat, is the major determinate of resting Caloric consumption. Cunningham nicely demonstrated that Lean body Mass (LBM) i.e. muscle mass, was the single best predictor of BMR. He provided an alternative equation to determine replacement Calories for an individual's BMR that was sex independent (once the LBM was calcualted): BMR(cal/day) = 500 + 22 (LBM).

Let's digress for a moment and address three common misconceptions about the BMR.

• First BMR drops in the winter. The BMR is determined by total body weight and the amount of muscle mass (fat and muscle tissue burn Calories at different rates), not the ambient temperature. Requirements to maintain your body temperature in a cold environment are IN ADDITION to this basal rate which remains unchanged.

• Second, BMR cannot be modified aside from increasing your muscle mass. Not true, Van Pelt et al did demonstrate that BMR (adjusted for LBM) will vary depending on the baseline energy expenditure (exercise volume) per week.

• Third, experienced or trained athletes can "tune" their metabolism and become more efficient. Untrue. A trained athlete will become smoother in style, and adopt other energy saving techniques, but their basic energy needs for any level of energy expenditure (or Caloric output) while exercising are the same as you and I.

• Finally, metabolism slows with age. BMR does drop with age, but this is related to a loss of total muscle mass, rather than the aging process itself. Generally people lose about 25% of their lean body mass per decade after the age of 30 and will, in concert, drop their BMR by 2 to 3 % per decade. And the drop in BMR is entirely explained by that drop in muscle mass from inactivity. Van Pelt et al, in a comparison between young and older trained men having the same fat free body mass and similar levels of daily activity, meaures of the BMR were similar. So keep on exercising!