A few months ago there was a discussion going on about proper rest periods between sets. To me this answer to this question is very simple, although a bit anecdotal. However, if you have ever walked into a gym and actually lifted weights, you should easily find that the closer you get to your 1 RM (single rep max) the more recovery you need for the next set. Never the less, there were some that insisted on answering this question by turning weight lifting into a rocket science. We toss about several magical formulas and never did reach any conclusions.
Well for all of those that are still interested in proper rest periods, it's explained in the literature as follows: As strength gains increase, rest periods also increase, which is related to relative training intensity.
For those of us who absolute insist on a scientific explanation, the available research explains this theory by saying that ATP recovery actually requires 3 to 5 minutes, and phosphocreatine recovery occurs within 8 minutes. Both directly influence subsequent exercise intensity. High intensity exercise also results in lactic acid and hydrogen ion (H+) accumulation and can disrupt sodium (Na+), potassium (K+), calcium (Ca++), magnesium (Mg++), and chlorine (Cl-1), and other anions such as proteins and phosphate ions resulting in a lowered intracellular pH. These disturbances can contribute to muscle fatigue. Shorter rest periods of less than one minute between sets can produce marked increases in serum lactate. The time needed for cellular lactate ion and H+ efflux has been shown to be 4 to 10 minutes.
So in order to be complete recovered for the next set one must surely consider the above mentioned facts. It should be noted that optimum rest periods for a given intensity have not been established. But it is obvious that the type of exercise, number of reps per set, and other factors may will affect this time. However, if you are working with 90%+ 1 RM, I would say it would be a safe bet to wait between 3-5 minutes. If you are doing multiple sets at that intensity I would push the time up to around 6-8 minutes to allow for complete efflux of lactic acid accumulations.
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