The body ages at different rates, but one thing you can influence is your strength! Research shows that ageing occurs in distinct biological leaps. Physical capacity starts to decline as early as 35, but regular strength training, with adjustable weights for progression, is one of the most powerful tools to slow down the process, no matter when you start.
Strength training is a well-researched method to counteract loss of muscle mass and many other health aspects such as metabolic, skeletal and joint function. Maintaining and building muscle mass, regardless of age, is directly linked to independence, mobility and quality of life.
The good news, according to a study at Karolinska Institutet, is that it is never too late to start. The body responds to strength training at any age. The effects may not always be visible in the mirror, but they are noticeable in how you move, how you feel and how you cope with everyday life.
Read more about strength training for seniors.
A study from Stanford Medicine, published in Nature Aging, examined molecules in samples from the blood, skin and intestines of 108 people aged 25-75. The results showed that as many as 81% of the molecules studied did not change continuously, but made clear leaps at about 44 and 60 years of age.
At 44, there are changes in metabolism, in adipose tissue proteins, and in the connective tissue proteins that hold muscles and skin together. This may explain why we suddenly notice that we are less able to tolerate alcohol, that cholesterol levels rise and that it takes longer to recover from exercise.
At 60, there are also changes in kidney function and the immune system, which probably contribute to a marked increase in cancer, cardiovascular disease and infections at that age.
It is important to note that the study has limitations: participants were recruited only from California, no one was over 75, and causal relationships were not mapped. However, the results are consistent with previous research that has pointed to similar patterns in ageing.
In another study, the Swedish Physical Activity and Fitness study (SPAF), researchers at Karolinska Institutet followed 427 people in Sweden for almost 50 years. Participants were randomly selected and from the age of 16 to 63 their fitness and strength were regularly measured.
The study shows that the decline in physical capacity starts as early as 35 years of age, regardless of the amount of exercise, and that the rate of decline then increases with age.
However, the study also shows that individuals who increased their physical activity in adulthood improved their performance by 5-10%. Physical activity cannot stop the decline, but it can slow it down significantly. Moreover, the differences in physical capacity at 63 were significantly larger than at 16, suggesting that lifestyle choices play an increasingly important role as we get older.
Start early, but it's never too late! People who exercise regularly in their 30s and 40s build up biological capital that pays dividends for the rest of their lives. But the body is still malleable well into old age. And every workout counts.
Continuity beats intensity. It's not a single workout that makes the difference, but what you do week after week, year after year. Easily accessible exercise, such as outdoor gyms in your neighborhood, workplace or natural environment, lowers thresholds and increases the chance that exercise habits will stick.
The differences are social, not just biological. The increasing differences between individuals over the years do not appear to be solely physical. Access to exercise, economic conditions and living environment all play a role. This makes the issue of physical activity a public health and equity issue.
Everyone ages, but how we age and how fast depends largely on how we use the body we have. That's one of the strongest arguments for making weight training with adjustable weights available to everyone, not just those who have already found their way to the gym.
Sources:
Shen X, et al. (2024). Nonlinear dynamics of multi-omics profiles during human aging. Nature Aging. Stanford Medicine.
Westerståhl M, et al. (2025) Rise and Fall of Physical Capacity in a General Population. Karolinska Institutet.