Timed Static Contraction Belt Squat

Q&A: Training to Failure on Timed Static Contractions

Question: How do I know if I am training hard enough to reach momentary muscular failure (MMF) when doing a timed static contraction (TSC)?

I often begin to shake when performing TSC. Does that mean I’m at momentary muscle failure?

I bought your book Timed Static Contraction Training: A Guide to Minimalist High Intensity Isometrics and I´ve been training using that as guide.

Answer: MMF occurs when you are unable to continue performing an exercise in the prescribed manner. This is the point when you are unable to continue lifting in strict form when performing dynamic exercises, and the point when you are unable to prevent the weight from lowering during static holds. The main reason working to MMF is recommended during these kinds of exercises is because it guarantees you have worked the target muscles as intensely as possible (as hard as possible relative to their momentary ability).

MMF doesn’t happen when performing TSC because you’re contracting against an immobile or unyielding object for a predetermined amount of time instead of lifting or holding a weight until you can’t. TSC is typically performed in three phases of increasing effort, starting with a moderate or 50 percent effort, then increasing to hard or 75%, and finally maximum effort. When you contract as hard as you can during this last phase you accomplish the same thing you do when working to MMF during dynamic exercises and static holds.

Timed Static Contraction Belt Squat


If your muscles shake during exercise it is because they are becoming deeply fatigued. Normally, your body recruits exactly the number of motor units (groups of muscle fibers sharing a motor neuron) needed to produce the desired amount of force for the movement you are performing. As some become fatigued others are recruited to take their place. Normally this happens pretty smoothly, but the more fatigued you become and the more and larger the motor units dropping out the more the force produced varies from the target and you start to shake.

The degree of shakiness relative to fatigue can vary a lot between individuals and even between muscle groups within individuals though, and is not a reliable indicator of how hard you’re working. I often shake after only one or two reps when performing upper body pushing exercises, but very little during other exercises. I’ve trained some people who shake from the start on certain exercises and others who don’t shake at all.

Don’t worry about either MMF or shaking during TSC. If you want the best possible results from TSC just commit to consistently giving everything you’ve got during the final, maximum-effort phase.

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