Can fitness genes explain differences in workout results?

In a session at the 22nd Annual Congress of the European College of Sports Science, Dr. Bernd Wolfarth, professor in the Department of Sports Medicine at Humboldt University, Berlin, explains, “Environment is a major factor [for trainability], and nowadays, we know that about 25–40{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of the variability of phenotype results from genes, and the other 60–75{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} is coming [from] environmental effects.”

Specific genes called candidate genes may predict successful responses to targeted types of exercise training. These genes may influence energy pathways, metabolism, storage, and cell growth in the body.

These findings led researchers from the Cambridge Centre for Sport and Exercise Sciences at Anglia Ruskin University, UK, to conduct a meta-analysis to identify the specific version, or alleles, of candidate genes related to the exercise response in untrained participants. The team analyzed strength, anaerobic power, and cardiopulmonary fitness.

Individuals inherit one allele of each gene from each parent. The individual is homozygous for the gene if both alleles are the same and heterozygous if the two alleles are different.

The study also assessed whether the identified genes and alleles contributed to differences in exercise training response among the participants. The researchers analyzed the results from 24 different studies with a total of 3,012 participants. Of the cohort, 1,512 participants were male, and 1,239 were female. The sex of the remaining 261 participants was not stated.

The mean age of the participants was 28 years. There were 89 groups: 43 aerobic, 29 strength, and 17 power. The researchers identified 13 candidate genes and alleles, of which nine, six, and four were associated with cardiorespiratory fitness, muscular strength, and anaerobic power, respectively.

On average, the participants in the cardiorespiratory fitness studies received aerobic training for 36 minutes on 3 days of the week for a total of 12 weeks. The specified intensity was 77{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of maximum heart rate or 74{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of VO2 max. The researchers attributed 44{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of the difference in aerobic training response to genetic influences.

Strength training, on average, involved 174 repetitions per session at an intensity of 75{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of one-repetition maximum. Sessions took place 3 days per week for a total of 10 weeks. Genes accounted for 72{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of the observed differences in the strength training group.

The participants in the anaerobic power group performed, on average, 4–12 cycle bouts of a specified intensity — 90–110{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} VO2 max or a load of 0.075 per kg body weight — 3 days a week for 5 weeks. Genes had less influence in the power group, with only 10{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of the variability in response being due to genetic influences.

Dr. Bert Mandelbaum, who is a sports medicine specialist and orthopedic surgeon at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles and was not involved in the study, told Medical News Today, “Genomics and the aspects of […] phenotypic and genotypic expression […] with respect to fitness and exercise are now being associated with a variety of genomic patterns.”

“As we learn more about [the] phenotypic expression of a variety of haplotypes in genes, there [will] be a spectrum of how we interpret these […] going forward — this is one of those studies that really demonstrate that.”

The strengths of this meta-analysis included the classification of study groups as either aerobic, strength, or power and the assessment of gene subgroups. As the sample size for some genes was small in this review, further studies are necessary to determine the exact role of these genes in influencing cardiopulmonary fitness, strength, and anaerobic power.

The results of future research may, theoretically, support the individualization and optimization of exercise programs based on a person’s genetic makeup.

Henry C. Chung, lead author of the study and Ph.D. researcher, states:

“Because everyone’s genetic makeup is different, our bodies respond slightly differently to the same exercises. Therefore, it should be possible to improve the effectiveness of an exercise regimen by identifying someone’s genotype and then tailoring a specific training program just for them.”