Top-level athletes with nasty injuries often recover surprisingly fast. How come? A human study published by sports scientists at the University of Copenhagen in the Journal of Physiology points to the probable answer: growth hormone.
Six years ago the coach Sal Marinello wrote a column in the Healthy Skeptic [The Healthy Skeptic Jul 25, 2006] in response to an article in Muscle & Fitness about the football player Terrel Owens. Owens had made it known that he had been given preparations that boosted recovery of his joints. Marinello smelled a rat. Might Owens be getting growth hormone, or IGF-1? Both substances are on the doping list.
Rumours of the use of forbidden substances to speed up recovery from injury have been doing the rounds in the sports world for years. In 2010 Danish researchers published the results of a human trial, which indicate that there may be some truth to the rumours.
The Danes gave 10 healthy men aged 30 a daily injection of human growth hormone for 14 weeks. They used Norditropin from the Novo Nordisk factory. During the first week the men were given an injection every day containing 33.3 micrograms growth hormone per kg bodyweight, and in the second week they were given 50 micrograms per kg bodyweight.
Before and after the course of growth hormone the researchers extracted samples of tissue from the muscle attachments in the men's knee joint and from their quadriceps. On one occasion this was done 24 hours after that the men had 'trained' their legs, doing a set of leg extensions; on the other occasion it was done after the men had done no exercise.
The course of growth hormone injections boosted the production of collagen in the knee joint, as the figure below shows.
Growth hormone had no effect on the protein fibres responsible for muscle contraction [myofibrillar protein]. But the growth hormone did stimulate the production of muscle collagen, as the figure below shows. So growth hormone itself doesn't make muscles stronger, but it does create the conditions under which muscles are able to grow stronger.
So it may well be the case that torn muscles and damaged muscle attachments heal more quickly if growth hormone is administered, the Danes suggest. It's not a completely new idea. There are a couple of animal studies in which growth hormone has been shown to boost recovery of damaged cartilage [BMC Physiol. 2007 Mar 26; 7:2.] [J Orthop Res. 2002 Sep; 20(5): 910-9.] and there are a couple of human studies that also point in the same direction. Spanish doctors for example have had some success in treating athletesí torn Achilles tendons with a ****tail of growth factors, including IGF-1. [Am J Sports Med. 2007 Feb;35(2):245-51.]
"In this study, just 14 days of rhGH supplementation in healthy individuals increased collagen synthesis by up to 6-fold without causing any side effects", the Danes write. "An increase of this magnitude holds clinical perspectives in relation to traumatic musculoskeletal injuries, where the collagen matrix inevitably is damaged."
J Physiol. 2010 Jan 15;588(Pt 2):341-51.