On January 9, 2022, Dr Kevin Tipton passed away. I have written a tribute (click here) to describe my stories and memories of many years of friendship and several years of working together at the University of Birmingham. Kevin was regarded as one of the world’s leading experts in protein metabolism. He was particularly interested in what happened after exercise and what we could do to improve recovery and adaptation in the muscle.
In this blog I want to highlight 5 of his most important scientific papers. There may be other papers that have been even more impactful. But these are my personal top 5. These papers hugely helped our understanding of protein metabolism and influenced the recommendations we give to athletes.
Paper 1: Muscle protein turnover after exercise
Increased rates of muscle protein turnover and amino acid transport after resistance exercise in humans. Gianni Biolo, Sergio P Maggi, Bradley D Williams, Kevin D Tipton and Robert R Wolfe . Am J Physiol 268: E514-E520, 1995
This was one of Kevin’s very first scientific publications. Gianni Biolo is the first author and Bob Wolfe was the senior author on this paper from a study performed in Galveston Texas. The main finding of this paper was that after exercise both protein synthesis and degradation are increased. This was an invasive study that used a new method of stable isotopic tracers, arteriovenous catherization of the femoral vessels (essentially drawing blood from an artery and a vein in the leg) in combination with biopsies of the vastus lateralis (quadriceps muscle). The paper debunked the simplistic view that is often communicated: during exercise muscle protein breakdown is increased and after exercise you make new proteins. This is an oversimplification. Both breakdown and synthesis are increased after exercise, and there is an increased turnover. This is likely because damaged proteins need to be broken down first and then replaced with new ones. The study also suggests that blood flow to the leg plays a very important role in delivering amino acids, which may facilitate the transport of those amino acids into the muscle. This paper may not have changed the recommendations to athletes immediately, but it helped our understanding of how the recovery/adaptation process works.
Paper 2: Protein metabolism over 24 h
Acute response of net protein balance reflects 24h balance after exercise and amino acid ingestion. Kevin D Tipton, Elisabeth Borsheim, Steven E Wolf, Arthur P Sanford and Robert R Wolfe. Am J Physiol 284: E76-E89, 2003
This is the first study (at least that I am aware of) that looked at 24 hour protein metabolism in exercising individuals with and without amino acid ingestion. Most studies had performed measurements for 3 or 4 hours after exercise. But it always was a big question whether what you measure in 3 hours can also be extrapolated to 24 hours or longer. In other words if I measure that I can increase muscle protein synthesis over 3 hours after resistance exercise by a particular nutrition intervention, does this mean that it will also do this over 24 hours ? and will this ultimately result in more muscle mass?
These studies are very hard to conduct because stable isotope tracers have to be infused intravenously for 24 hours, diets need to be standardized, exercise needs to be supervised and so on. Kevin had some great stories about this study. Not only was this study quite invasive (with arteriovenous differences across the leg, infusion of stable isotopes and muscle biopsies), they were also difficult because of the sampling that needed to occur around the