Calorie Expenditure

Heart Rates for Energy Expenditure

Weight loss is difficult. Not in theory – eat less and move more – but in implementation. One of the major obstacles for most people is the lack of knowledge and/or confusion surrounding caloric intake and expenditure. Most people consume more calories than they realize and burn far less calories than they expect. Knowing what (# of calories) is actually in the foods they consume is one problem and knowing how calories are referenced is another. A breakfast muffin for instance may have 400-600 kcal. While the label says 200 kcals/serving, some overlook that the label also states there are two servings per muffin. At quick glance the calories and fat presented are only half of the actual value. A similar problem occurs in the gym. The Stairclimber shows 300 kcal after a 30 minute workout. In reality, the value is only correct if the individual maintained an upright posture, did not lean on the machine, and maintained proper pace and range on the pedals; or more importantly sustained heart rates. Just like the serving and portion sizes matter in food, heart rate matters when performing continuous exercise aimed at achieving weight loss.

After 50% of VO₂max, heart rates correlate increasingly well with VO₂ at the same intensity. The chart below demonstrates the relationship between the percentage of measured heart rate and percentage of VO₂max. The percentage of heart rate max is always charted on cardio machines and the general recommendation is to train between 75-90% of HRmax, or 60-80% of VO₂max, which is explained by the number correlations below. The reason this is relevant is caloric expenditure is tied to oxygen utilization. If you know a person’s VO₂ you can also determine an actual caloric expenditure by minute based on heart rates.

Percentage of HRmax	Percentage VO2max
66%	50%
70%	55%
74%	60%
77%	65%
81%	70%
85%	75%
88%	80%
92%	85%

Many fitness professionals have realized by now that the Elliptical Trainer and other static modalities do not predict energy expenditure accurately and based on usage dynamics commonly over-predict the caloric expenditure – giving clients a false sense of accomplishment and frustration at the lack of results at the same time. To correct this issue the first step is identifying how many calories a person can actually expend. Walk and run tests can do this with acceptable accuracy and present viable numbers to work with for weight loss.

-National Council on Strength and Fitness