Saturday, June 9, 2012

Are there genetic biomarkers to predict adaptability to training?

The study of genetic contribution to exercise training adaptation has emerged over the last years in an attempt to identify possible genes that regulate adaptability to training or trainability. These studies aimed to improve knowledge on effective health-related interventions and, hence, were on general population or unhealthy individuals (McPhee et al., 20120; Timmons et al., 2005).  However, information from these studies might shed more light into the potential molecular mechanisms explaining the observed large variability in training adaptations. Accordingly these findings might contribute in improving our understanding on why some players improve more than others.

Indeed, variability in maximum aerobic power improvement after training has been reported to range from 0% to >100% (Timmons et al., 2010). This means that some individuals show a big improvement whereas others no improvement at all. Causes of this wide range of inter-individual variability are poorly understood. Timmons et al. (2010) in his pioneer study has identified key genetic links to such variation. The authors defined a 29-gene expression signature in untrained skeletal muscle that explained >50% of the variance in VO2max improvements due to training.

One year later, Professor Claude Bouchard, a leader in genetics, identified genomic predictors of the response of VO2max to regular exercise. Interestingly, these genomic predictors were different from those presented by Timmons et al (2010). In Bouchard’s study, subjects who carried <9 favorable alleles at these 21 single-nucleotide polymorphisms (SNPs) improved their VO2max by 221 ml/min whereas those who carried >19 of these alleles improved by 604 ml/min. The 21 SNPs identified as predictors explained 49% of the variance in VO2max trainability. Although, the pre-training absolute values are not presented in this paper these results explain why there is such variation in human adaptive response to exercise training.

Conclusions and practical applications
  1. From these studies it appears that part of the variation in adaptation to exercise originates from variation in gene sequence that influences the complex cascade of biochemical events leading to adaptations to training.
  2. If there are genetic predictors of adaptation to training this means that in the future we might be able to select among talented players those with “high trainability”. We might also be able to create more effective training regimes for “low responders” but skilled players.

Points to consider before final conclusions
  • Studies so far have been conducted with white, non-elite athletes. We know very little for athletes and especially non-whites.
  • Most of the information is on VO2max although some data exist on resistance training adaptations. There is very limited information on other fitness attributes that have high impact on football performance.
  • As the authors of these papers acknowledge the relatively small sample size for this kind of research is a limitation of these studies. This however does not undermine, in my opinion, their significant contribution in advancing our current knowledge.

Bouchard et al. Genomic predictors of the maximal O2 uptake response to standardized exercise training programs. Journal of Applied Physiology 110: 1160-1170, 2011.
McPhee et al. Inter-individual variability in adaptation of the leg muscles following a standardized endurance training programme in young women. European Journal of Applied Physiology 109:1111-1118, 2010.
Petrella et al. Potent myofiber hypertrophy during resistance training in humans is associated with satellite cell-mediated myonuclear addition: a cluster analysis. Journal of Applied Physiology 104: 1736-1742, 2008.
Timmons et al. Human muscle gene expression responses to endurance training provide a novel perspective on Duchenne muscular dystrophy. FASEB 19:750-760, 2005.
Timmons et al. Using molecular classification to predict gains in maximal aerobic capacity following endurance exercise training in humans. Journal of Applied Physiology 108: 1487-1496, 2010.

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