A recent long-term study has found that measurable declines in physical fitness and strength begin around age 35, challenging the common belief that such declines are only associated with old age. The research, which tracked participants for nearly 50 years, is part of the Swedish ‘Physical Activity and Fitness’ cohort that began in 1971 with individuals born in 1958.
The study, conducted by researchers at the Karolinska Institutet, involved 427 individuals, including both men and women. It aimed to monitor changes in aerobic fitness, muscle strength, and physical activity habits throughout adulthood. As participants aged, they underwent standardized physical testing at various points, allowing researchers to observe individual changes over time rather than relying on comparisons between different age cohorts.
Declines Observed Across Multiple Fitness Measures
At each examination, participants underwent tests to measure their aerobic fitness, which was assessed through peak oxygen uptake, a key indicator of cardiovascular capacity. Muscle strength and endurance were evaluated with controlled performance tests, including grip strength and repetitive movement tasks. Basic physical measures such as height and weight were also recorded, and participants provided insights into their physical activity habits.
The findings reveal that physical performance peaks during early adulthood but begins to decline steadily after the mid-30s. This trend was consistent across various fitness measures, including aerobic capacity and muscle strength. Although individuals who maintained a physically active lifestyle tended to preserve higher fitness levels, the study found that physical activity could not entirely prevent age-related declines.
Importantly, the data indicated that participants who increased their activity levels later in life were able to enhance their physical capacity by approximately 5% to 10%. This suggests that the body remains responsive to exercise even beyond peak years.
Study Limitations and Future Directions
Published in the Journal of Cachexia, Sarcopenia and Muscle, the study has some limitations. The cohort consisted primarily of individuals born in the same year and residing in Sweden, which may limit the applicability of the findings to other populations with different social or genetic backgrounds. Additionally, the observational nature of the study means that other factors, such as diet and health conditions, may have influenced the results.
The researchers acknowledged that participant dropouts over the long study period could also affect the sample’s representativeness. Moreover, while physical activity correlated with better outcomes, the study did not capture short-term fluctuations in physical performance between testing intervals.
Looking forward, the research team plans to continue following the cohort as participants age. Their objective is to link changes in physical capacity to health outcomes later in life, providing further insights into the relationship between fitness and overall well-being as people grow older.
As the study illustrates, understanding the onset of physical decline can help individuals make informed decisions about their health and fitness strategies earlier in life.
