We say it again and again through the studies we choose to include on the site, physical activity is essential to prevent many health problems and improve the quality of life. The official recommendations of the WHO clearly indicate that at least two weekly sessions of resistance training are necessary. Indeed, scientific studies show that muscle strength is inversely correlated with cardiovascular risks and mortality. In addition, low muscle strength also limits general mobility and can cause problems in daily activities.
With an increased sedentary lifestyle and a lack of physical activity, maximum muscle strength seems to decrease from the age of 40, and more strongly between the ages of 50 and 70, sarcopenia and fragility are direct consequences of this phenomenon. However, resistance training can help to fight against these deleterious effects. Training with relatively heavy loads (> 85% of the 1RM) seems to be the best alternative (compared to relatively light loads) to increase maximal strength, whether in young or older people, in men or women. However, many studies have already reported a great heterogeneity of responses to training, with not everyone obtaining the same strength gains despite a similar training program. This disparity in results could be explained in part by the influence of genetics. But this part is not completely understood because there are over 200 genetic polymorphisms (variations in genes) currently known to be associated with strength and power phenotypes. What is the truth of this? Does maximal strength training benefit everyone? Regardless of age, gender, or genetics ?
To answer these questions, a team of researchers studied the response to maximal strength training as a function of age, sex and certain genetic variants. To do this, 49 people (27 women and 22 men) between the ages of 20 and 76 participated in a maximal strength training program that lasted 8 weeks. The program was the same for all and consisted of performing 3 sessions per week of 4 sets of 4 repetitions at an intensity corresponding to 4RM on a leg press (up to 90° of knee flexion). Each time a person could perform 5 repetitions in a set, 2.5-5 kg were added to the next set. Before and after the 8-week program, all participants assessed their 1RM on the leg press. For the results analysis, the participants were divided into 5 groups according to their age: 20-29 years, 30-39 years, 40-49 years, 50-59 years, and 60+ years.
A blood sample from each person was collected to analyze 3 genetic variants related to strength and power, which are among the most studied in the scientific literature: ACE I/D (rs1799752) involved in blood pressure regulation and locally in muscle function, ACTN3 (the so-called "speed gene") R577X (rs1815739), and PPARGC1A (encoding PGC-1α, a major regulator of mitochondrial biogenesis but possessing other isoforms involved in other metabolic pathways) Gly482Ser (rs8192678).
The main results of this study show that after 8 weeks of training, leg press 1RM increased similarly for all participants, regardless of age, gender, baseline strength level or genetic profile (partially). On average, participants increased their maximal strength level by 24.2 ± 14.0%, with no participant achieving less than a 7.4% improvement :
Concerning genetic polymorphisms, no significant association was observed between ACE I/D (rs1799752) and ACTN3 R577X (rs1815739) and 1RM progression. This would mean that regardless of phenotype, progression in maximal strength would not depend on these two polymorphisms. On the other hand, concerning PPARGC1A Gly482Ser (rs8192678), only carriers of the C allele increased their 1RM in the leg press more than those with the TT genotype. Yet, carriers of the T allele had a higher baseline 1RM than those with a CC genotype. In the scientific literature, the T allele is often associated with an athlete's strength/power level, indicating an advantage in gaining strength. These conflicting results could be explained by the greater margin of progression of individuals carrying the C allele, but statistical results did not show a correlation between baseline 1RM level and progression. Another possible explanation is that resistance training results in the expression of the PGC-1α4 isoform that regulates muscle hypertrophy. But the study does not link the expression of this isoform to PPARGC1A Gly482Ser (rs8192678).
Maximal muscle strength is related to motor function, balance and overall quality of life. Like maximal oxygen consumption (VO2MAX), the level of maximal strength is inversely correlated with cardiovascular risk and mortality. And this study demonstrates once again that regardless of age, gender, fitness level or even genetics, specific strength training can increase maximal strength. Of course, in this case, only 3 polymorphisms out of more than 200 known to be related to physical performance were tested, and only one of them showed a link with the results obtained.
That being said, while genetics has a strong influence on our bodies and abilities, it does not code for the decisions we make or the actions we take. The results of this study show that it is very rare that a person cannot achieve positive strength results by following a proper program and training long enough, regardless of age, gender or baseline level. This is not about becoming a strongman or powerlifter, but about achieving relative strength gains that will benefit us daily, and throughout our all life.
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