As you will undoubtedly be fully aware, Britain is hosting the London 2012 Olympic Games. To mark this historic occasion, The Physiological Society (in association with the British Pharmacological Society and John Wiley & Sons) has organised a three-day international scientific meeting in central London (19–21 March) to showcase world-leading exercise physiology and medical research focused on human exercise and performance. The Journal of Physiology has played a major role in supporting this event and this is continued by the publication of this special issue highlighting the Exercise Metabolism Symposium from the second day of the meeting.
In 1948, the occasion of the 14th summer Olympics, the last time Britain hosted the games, the men's marathon gold medal was won by Delfo Cabrera in 2:34:52 in a dramatic finish that saw the first athlete to enter the stadium, Etienne Gailly, finishing exhausted in third place. Even more dramatic, was the feat of Fanny Blankers-Koen who won gold medals in the women's 100 m, 200 m, 80 m high hurdles and 4 × 100 m relay, and resulted in her being credited with the perhaps unflattering moniker ‘The Flying Housewife’. Since this time, and by way of example, the men's Olympic marathon record has tumbled to 2:09:21, and it is irrefutable that a significant part of this advance in sporting performance over the intervening 64 years is directly attributable to scientific advances in our understanding of the physiological basis of human exercise metabolism, adaptation and performance. It is fitting therefore that this issue of The Journal of Physiology is devoted to leaders in the field highlighting some of these major scientific advances and elegantly summarising where gaps in our knowledge still remain. It is also pleasing to note that The Journal has played a role in documenting these events by publishing many of the original papers cited in these review articles.
This Special Issue of The Journal starts with a paper from my colleagues, Philip Atherton and Kenneth Smith (Atherton & Smith, 2012), which summarises our current understanding of the impact of nutrition and exercise on muscle protein synthesis in humans and how these two physiological stimuli can interact, in the short term at least, to maximize muscle protein accretion. This thought provoking commentary goes on to highlight the molecular regulation of human muscle protein synthesis and underscores how our current understanding is in its infancy, and particularly so in the context of chronic adaptation of muscle to nutritional and/or exercise intervention. This latter point will be received with some disbelief by many given the ongoing overabundance of nutritional and exercise regimens advocated to maximize muscle mass gains.
The review article of Jacob Jeppesen and Bente Kiens summarises current opinion on how fatty acid metabolism is regulated during exercise, and focuses on the contentious issue of what exactly limits muscle fatty acid oxidation during the transition from moderate to high intensity exercise in humans (Jeppesen & Kiens, 2012). By using a process of logical, evidence based elimination, the authors conclude that free carnitine availability is the principal limitation in the fatty acid oxidation in the transition from moderate to higher intensity exercise. Research over the coming years will hopefully confirm whether this is indeed the case, as this aspiration has significant implications for scientific understanding beyond the sporting context, such as ageing and obesity.
Continuing, but not at all unrelated given the reciprocal relationship between fat and carbohydrate oxidation during exercise, Thomas Jensen and Erik Richter update us on the molecular signals by which muscle glucose transport is increased by exercise and the control of glycogen mobilization and synthesis by glycogen phosphorylase and glycogen synthase (Jensen & Richter, 2012). Highly relevant to our understanding of human performance, the authors also bring us up to date with insight concerning the molecular basis of the phenomenon of muscle glycogen supercompensation, discovered in the 1960s by Jonas Bergstrom and Eric Hultman, and widely used by endurance athletes to maximize performance gains.
Finally, Martin Gibala, Jonathan Little, Maureen MacDonald and John Hawley provide an overview of the step-wise change to our understanding they, amongst others, have provided by demonstrating the effectiveness of high-intensity interval training (HIT) in promoting human physiological adaptation (Gibala et al. 2012). Indeed, they outline how HIT has been shown on several occasions to produce greater adaptation than traditional endurance-based training, but with a substantially lower time commitment and reduced total exercise volume. This is a field in its infancy, with mechanistic insight underpinning the effectiveness of HIT yet to be revealed, but clearly the public health implications are exciting and substantial.
There can be no doubt that this special issue of The Journal will be a major attraction to researchers and students world-wide who are concerned with human metabolic and exercise physiology, not least because of its breadth and depth of insight and the contemporary nature of its content. I hope you gain the same sense of enjoyment and excitement that I felt when first reading these articles, but moreover that you acquire the realization that considerable gaps in our knowledge remain to be filled. There can be no greater stimulus to young scientists entering the field.