When doing bicep curls, the first rep is relatively easy but eventually it becomes impossible to do a single curl.
After a rest, the muscle resets and can once again lift.
What is causing the muscle exhaustion and what is it that “resets” within the muscle?
In: 85
Your muscles are running low on rapidly available energy and need to replenish it, [Here is a graph that shows energy sources during strenuous activity](https://www.researchgate.net/publication/333902223/figure/fig3/AS:1086068711530568@1635950367918/The-energy-systems-that-contribute-to-sport-practice-The-phosphagen-system-ATP-CP-is.jpg).
You start out with ATP (energy carrier of the cell) floating around but this is depleted within a second or two. Phosphocreatine then can regenerate some of the ATP while glycolysis ramps up. So far no oxygen was needed but now the muscle has depleted its phosphocreatine reserve and has begun to generate lactic acid as a byproduct of regenerating a reactant of glycolysis called NAD. This process slows as lactic acid builds up and glycolysis will slow due to a lack of NAD.
Now you have reached the point where you cant lift any more, your muscles have run out of available energy. If you wait a little bit the lactic acid will be carried away by your blood and metabolized in the liver. Meanwhile the muscle regenerates phosphocreatine and ATP levels return to normal and you are ready to lift more weight.
Latest Answers