If athletes become aware that high-reps strength training can help them build up muscle mass and may also delay a wide range of aging processes then this form of strength training may well become popular. If this does indeed happen, then it's also important that trainers know that high-reps strength training taxes muscle fibre so much that untrained people can develop dangerous levels of muscle damage. Untrained individuals should give their body time to adjust to high-rep strength training by building workouts up slowly.
American sports scientists who are studying high-reps strength training got participants to train their biceps with 30 percent of the weight with which they could manage 1 rep. The participants did 3 sets of 30-40 reps.
Creatine kinase is an enzyme that should not be present in high concentrations in the bloodstream. It enters the bloodstream however when muscle cells tear open. A normal creatine level is 45-260 units per litre. At a concentration above 5000 units doctors start to think of rhabdomyolysis. The woman's level was way above that.
The urine of people with too much myoglobin in their blood becomes the colour of tea or Coca-Cola. This was not the case in the 21-year-old woman. The doctors sent her home and told her to drink lots of water and take paracetamol - rather than aspirin, naproxen or ibuprofen. Paracetamol is milder for the kidneys than the other painkillers.
It took two weeks for the women's biceps to return to normal, which was confirmed by the doctors' scans.
The case described in this article is not an isolated incident. In 2015 trauma doctors at Baylor College of Medicine in the US also published a case study about a young woman who had developed rhabdomyolysis after a high-reps workout. [Case Rep Emerg Med. 2015;2015:281540.] In that case study the protagonist was a 23-year-old recreational athlete who, after several months of not training, had the unholy idea of treating her biceps to an intensive high-reps workout.
Doctors have also published other similar case studies in scientific journals. [Case Rep Emerg Med. 2015;2015:281540.] Some relate to athletes who were doing Kaatsu [J Strength Cond Res. 2016 Jul;30(7):2064-8.], others to athletes who combined high-reps training with intensive cardio exercise. [BMJ Case Rep. 2011 Apr 1;2011.]