Physics lesson for 'Time Under Tension'

In the late 1980’s, scientists discovered vital information that showed the stimulation of muscle growth and strength to be a function of ‘time under tension’ (TUT). However, the words from these studies had been taken too blindly by the fitness industry and this has caused huge confusion on how this data should be applied.

When Charles Poliquin promoted the concept, it took the bodybuilding world by storm. He taught that ‘time under tension’ means to lift lighter weights slowly through the concentric and eccentric phase, so then everyone suddenly began methodically timing their reps. Protocols such as 3-1-1 for strength or 5-1-5 for hypertrophy development became very popular. It’s easy see how people may interpret it that way given the lack of knowledge in biology and physics and in the case of ‘time under tension’, the term ‘time’ is the only word fitness professionals and bodybuilders seem to understand.

I think it became popular in the fitness industry,

  1. due to the lack on knowledge and understanding and
  2. because it forced sloppy lifters to slow down and gain control over what they are doing to have “good form”. Great teaching tool, great for rehab or isolating weakness. But for muscle growth and strength, absolutely not!

Newtons Laws

Given that my major when I was studying was physics, I think its appropriate I give you a small physics lesson starting with Newtons Second Law of motion.

Newton’s second law of motion can be formally stated as follows: The acceleration (a) of an object as produced by a net force is directly proportional to the magnitude of the net force(F), in the same direction as the net force, and inversely proportional to the mass (m) of the object. This can be simplified to F=ma where force equals mass times acceleration .

So to break it down

  1. Mass is large body of matter or in layman terms ‘weight’
  2. Acceleration is the rate in change of velocity in an increasing or decreasing state so basically the measurement of speed or how fast an object moves
  3. Force or net force is the overall force acting on an object, mass acceleration
  4. Tension, or intramuscular tension in physics describes the pulling/pushing force exerted by a cable or in this case the muscle.

So when it comes to ‘time under tension’ tension is calculated by mass X acceleration (force). In terms of weight training, the mass is what we refer to as the ‘weight’. Acceleration is the rate of change of speed of the weight (against gravity). The factor of time can be measured through volume which will need to be achieved in the shortest units of time for maximum velocity. So in simple terms: maximum intramuscular tension is created by lifting as heavy a weight as possible, as fast as possible through multiple reps and sets.

Basically, ‘time under tension’ is the scientists way of saying that power-bodybuilders had it right all along. Very heavy weights lifted explosively for multiple reps and sets is the key to maximum hypertrophy and strength. There are obviously lots of other factors that attribute to a good hypertrophy and strength program and tempo have other various applications but this blog is intended to address this particular misconception.