Understanding Volume and Intensity in Weight Training

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England Team Gym Session
England Team Gym Session. Tom Shaw/Getty Images

In weight training, the simple definition of volume is how much work you do, such as the number of reps you perform in an exercise. The simple definition of intensity is how hard the exercise is, generally based on the amount of weight or load you lift.

That's a simple approach, so I'll explain in more detail: If we take Romanian deadlifts, for example—let's say you do five lifts (repetitions) with 100 pounds—and you increase this to 10 lifts, you have increased the volume.

If you keep the repetitions at five but increase the barbell weight to 150 pounds, you have increased the intensity of the exercise.

The question is: How does this affect your workout? Are the results the same?

As with many things in the sports and exercise sciences, the answer isn't necessarily black and white. The answer can change according to a variation of input.

In this case, higher volume and constant load will tend to increase the work your heart and lungs do with the extra movement and effort over time. That's going to provide you with enhanced cardiovascular fitness, and at the same time give you some strength and muscle endurance and perhaps even a little more strength and muscle bulk, but not to the extent of the endurance factors.

On the other hand, if you increase the weight of the lift and keep the reps the same, you will gain only a little extra heart and lung condition but much more strength and muscle, especially if the weight is near to what you can tolerate for 10 reps.

It's a continuum according to each input of volume or intensity.

Measurement of Volume

Volume can be measured in the hours and minutes you train at the highest level, or in finer detail, by the number of sets and repetitions programmed in your workouts. If you do hybrid training that includes circuits or intervals interspersed with weights, then volume includes this work as well.

Volume of training, in simple terms, means intensity by time.

Measurement of Intensity

In lifting, intensity almost always refers to the weight you lift, in other words, how hard you work to make that one lift. If you do 20 reps, then you have increased the volume substantially, and ultimately your total work will increase if you raise either the weight or the number of reps or sets.

If you do circuits where anaerobic running or movement is required, then the rate of perceived exertion (RPE) or heart rate can be a guide to intensity. RPE is often measured on a scale of 1 to 10, where 1 is sitting still and 10 is as hard as you can go!

Heart Rate Measurement

As a general rule, intensity in relation to heart rate is measured as a percentage of your maximum heart rate (MHR). You can estimate your maximum heart rate as 220 minus your age, although this can be inaccurate for some people. You can also do a maximum treadmill session under supervision of a doctor or exercise physiologist to establish your maximum heart rate.

How vigorous you are working out in relation to your heart rate will depend on how fit you are. For example, for someone with cardiovascular disease, walking at a moderate pace might produce a heart rate of 70% of MHR, whereas someone with reasonable fitness might be able to jog or even run at a good pace and still only be at 70%.

For cardiovascular fitness training you should aim for 65-75% MHR, although fitter people can train at up to 85% without getting too far into the anaerobic training zone. In the anaerobic zone, your body uses more oxygen than it can reasonably take in through the lungs to support that level of intensity, and you pay it back in short order with exhaustion!

For high-intensity, anaerobic training you will train at 85% MHR and above. This is best done after you have achieved a reasonable level of all-round fitness.

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