Can fitness genes explain the differences in training results?



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New research is examining the role of genes and their variants in training outcomes. RunPhoto / Getty Images
  • Researchers at the University of Cambridge have published a meta-analysis in PLOS ONE identification of 13 candidate genes associated with fitness outcomes in previously untrained people.
  • Genetic influences accounted for 72% of the difference in results for people in the strength training group.
  • Genetic factors had less of an effect on results in the aerobic (44%) and anaerobic (10%) power groups.
  • More research is needed to determine the exact roles of fitness genes and how best to tailor physical training based on genetic makeup.

Physical activity is essential to maintain health, reduce chronic disease and prevent premature death. The 2018 Physical Activity Guidelines for Americans recommend a combination of moderate intensity and vigorous aerobic exercise, as well as muscle building activities involving major muscle groups.

The advice is for adults to do 150 to 300 minutes of moderate-intensity aerobic activity, 75 to 150 minutes of vigorous-intensity aerobic activity, or an equivalent mixture. They can spread this activity out throughout the week and should also engage in strength training at least 2 days a week to reap additional health benefits.

The three elements needed to determine health-related fitness are cardiovascular fitness, muscle strength, and anaerobic power. Cardiovascular or cardio-respiratory gymnastics Measures how efficiently the respiratory and circulatory systems provide skeletal muscle with oxygen for energy production during physical activity.

The maximal oxygen uptake (VO2 max) test is one way to determine cardiorespiratory fitness. The VO2 max test measures the body’s maximum oxygen uptake capacity during vigorous intensity activity, such as running on a treadmill.

A higher VO2 max indicates an improved ability to provide and use oxygen and to maintain aerobic activities at an increased intensity for long periods of time. Poor cardiorespiratory condition is a predictor cardiovascular disease and death from all causes in adults.

Muscle strength is the body’s ability to exert sufficient force against external resistance to perform tasks and maintain mobility.

Anaerobic activity is activity that involves breaking down glucose into energy without using oxygen. Anaerobic power measures the body’s ability to move with the greatest intensity over a short period of time.

Increasing cardiorespiratory fitness, muscle strength, and anaerobic power can improve a person’s overall fitness level, but responsiveness to training varies widely from individual to individual.

In a session at the 22nd Annual Congress of the European College of Sports Sciences, Dr Bernd Wolfarth, professor in the Department of Sports Medicine at Humboldt University in Berlin, explains: “The environment is a major factor [for trainability], and nowadays we know that about 25-40% of the variability in phenotype results from genes, and the remaining 60-75% comes from [from] environmental effects.

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

These findings led researchers at the Cambridge Center for Sport and Exercise Sciences at Anglia Ruskin University, UK, to conduct a study meta-analysis to identify the specific version, or alleles, candidate genes linked to 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 the two alleles are identical and heterozygous if the two alleles are different.

The study also assessed whether the identified genes and alleles contributed to the differences in response to exercise training between the participants. The researchers analyzed the results of 24 different studies with a total of 3,012 participants. Of the cohort, 1,512 participants were men and 1,239 were women. The gender of the remaining 261 participants was not specified.

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

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

Strength training, on average, involved 174 repetitions per session at an intensity of 75% of one repetition maximum. The sessions took place 3 days a week for a total of 10 weeks. Genes accounted for 72% of the differences seen in the strength training group.

Participants in the anaerobic power group performed, on average, 4 to 12 cycle periods of a specified intensity – 90 to 110% VO2 max or a load of 0.075 per kg of body weight – 3 days per week for 5 weeks . Genes had less influence in the power group, with only 10% 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, said Medical news today, “Genomics and aspects of […] phenotypic and genotypic expression […] in terms of physical fitness and exercise are now associated with a variety of genomic models.

“As we learn more about [the] the phenotypic expression of a variety of haplotypes in genes, it [will] be a specter of how we interpret these […] in the future – this is one of those studies that really shows it. “

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

The results of future research could, 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, says:

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


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