Constant Tension, Lactic Acid, and Muscle Burn

Jun 21, 2022

Photo Credit: Rafael Classen

Lactic acid doesn’t cause muscle burn, here’s why

At roughly 30% of maximal muscle tension, peripheral blood flow is significantly occluded resulting in increasing hypoxia within the blood (less oxygen availability) as time under tension increases. ⁣

During constant tension exercises like split squats

  • ATP is converted to ADP + phosphate + free hydrogen ions ⁣
  • The hydrogen ions have a positive charge and build up in the blood as the high-energy phosphate bonds are continually broken to fuel the muscle contractions
  • Hydrogen ion build-up, NOT lactic acid, is the cause of metabolic acidosis and therefore muscle burn during constant tension sets.

By contrast...

 During walking lunges:⁣

  • Blood flow is intermittently only very briefly occluded from muscle tension

Benefits of constant tension training

  • Lower load required (think deload, rehab setting, hotel gym with small dumbbells)⁣
  • Hormonal increases.... maybe (IGF-1, GH, MTOR, etc) ⁣

Downsides of constant tension training

  • Less mechanical load (not the ideal stimulus to improve maximal strength)⁣
  • More peaks and valleys in blood pressure⁣
  • Painfully difficult when performed correctly⁣

⁣Bottom line

  • Constant tension training doesn’t build up lactic acid
  • Constant tension training can be an effective training stimulus, but don’t put all your eggs in one basket

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