Resistance is what changes us. As the saying goes, if it doesn’t challenge you, it won’t change you. Challenges are a type of resistance. A resistance workout challenges our muscles. The greater the weight, the greater the resistance, the more our muscles are changed by overcoming the resistance. That’s one type of challenge. Another is lowering the weight but increasing the number of repetitions. These challenges are fundamentally different so one might assume that the muscle was changed in fundamentally different ways. While there are slight differences, there were no statistically significant differences in the changes to the muscle in the studies I found.
Work done equals force multiplied by distance. If you are using proper form and your full range of motion, workouts can be designed to have, for all practical purposes, the same amount of work done at 40-60% and 80-90% of your one rep max. But, here’s the thing. It takes more than twice as long to do a workout of 4 sets of 20-24 reps to fatigue at 40-60% of your one rep max compared to 3 sets of 5 reps to voluntary failure at 80-90% of your one rep max.
Power is different. Power equals work done divided by time taken. So more power is applied in the workout using 80-90% of your one rep max because it takes less time. So, why the physics lessons? Because power is measured in joules and 4.184 Kilojoules equals 1 Kilocalorie. Therefore, in a 44 gram (1.56 ounce) Snickers bar there are 215 “calories.” Really that means there are 215 Kcals or 215,000 calories. Another way to look at it is to say that there is is enough energy in a Snickers bar to raise the temperature of 215 liters by 1 degree Celsius. If you don’t use it. The energy is stored as fat. You would have to create 899.56 Kilojoules of power to burn the Kilocalories from that Snickers bar. That is a lot of effort.
Think about this idea of resistance. Changing a habit takes effort and work because the habit resists change. Overcoming the habit presents a challenge. If it doesn’t challenge us, it doesn’t change us. Or in this case, if we don’t challenge ineffective or destructive habits we don’t change.