This is a common question when I am teaching Weight Loss Solutions (WLS) class. Clients will ask me if they should increase the weight and go slower, or stick with the same weight/decrease the weight and go faster.
WLS:
First, keep in mind that the WLS class is intended for movement, with an emphasis on energy expenditure. With that said, this blog will provide some brief guidelines for WLS to maximize energy expenditure and to make sure you are getting the most out of the class.
Physics:
Let’s first go over a few concepts from high school physics. Mechanical Work is defined as a product of force and distance (Work= Force x Distance). Taken further, Force is simply MASS (or weight lifted) x ACCELERATION (or how quickly a given weight is lifted). The more work you can perform over a given time, the more energy you will expend. More WORK done equals more fat loss — bottom line.
Based on the above physics lesson, you can infer that there is some optimal combination of weight and reps to maximize energy expenditure. Conceptually, during the WLS class you want to go through the greatest range of motion (distance) with as heavy of a weight (mass) as quickly as possible. Keeping that in mind, a good goal is to perform 10 -15 reps every 30 seconds to get the most energy expenditure.
Range-of-motion:
Keep in mind that although this discussion is about weight and speed, range-of-motion (or distance the weight is moved) also plays a big role in work. Remember, Work equals Force x Distance. Although using a heavier weight and moving quickly is important, so is going through a complete range- of-motion. The greater the range-of-motion, the more tissue you stress and the greater the energy expenditure.
With all of this being said, I don’t want you going into WLS counting reps and slowing down because you’re doing 25 reps in 30 seconds. I would suggest intermittently counting your reps for each exercise during class, and if you find you are consistently exceeding 15 reps in 30 seconds, simply increase the weight (for non-body weight exercises).
Take Home Message:
So to answer the question, should I go heavier and slower-OR- lighter and faster, the answer is really both!!! You should go heavy enough to be physically challenged, but light enough to go fast. Go with the heaviest weight that you can lift for 10-15 reps, and lift it as quickly as you can through a full range of motion.