It’s tempting to dismiss observations about professional athletes maintaining high performance levels into their mid-30s and beyond, especially given the many older adults who continue to achieve personal bests and set new athletic world records. However, new research published in the Journal of Cachexia, Sarcopenia and Muscle provides clarity on this topic, identifying a specific age when fitness levels typically begin to peak, while also outlining effective strategies to extend fitness longevity. This insight is valuable for anyone, from those training for competitive age-group events to individuals simply seeking reassurance that their dedication to fitness contributes to a longer, healthier life.

The comprehensive study was conducted by researchers from Sweden’s Karolinska Institutet, who meticulously followed 427 participants over a span of nearly 50 years, ranging in age from 16 to 63 at the outset. Throughout this extensive period, individuals participated in a series of fitness and strength tests, including measurements of vertical jump ability, a common indicator of muscle strength, and various assessments of aerobic capacity. After rigorous data analysis, the researchers concluded that physical ability generally starts to decline as early as age 35.

Further analysis showed a notable drop in physical capacity, ranging from 30 percent to 48 percent, for participants between the ages of 35 and 63. Despite this observed decline, the study uncovered a crucial caveat: individuals who consistently remained physically active experienced a significantly slower rate of decline compared to those who were less athletic. This highlights the profound impact of lifestyle choices on the aging process of physical fitness.

Maria Westerståhl, PhD, lecturer at the Karolinska Institutet-Stockholm Department of Laboratory Medicine and lead author of the study, clarifies that the term “decline” should not be interpreted as an immediate and drastic loss of ability. She explains that once peak capacity is reached, the initial decrease is very gradual, progressing at approximately a 0.5 percent decrease per year. However, this rate of decrease accelerates with advancing age, surpassing 2 percent of capacity loss annually by age 60. In practical terms, this might manifest as a reduced ability to run as fast, jump over obstacles with the same ease, or lift and carry objects effortlessly. Dr. Westerståhl underscores a vital point: the stronger an individual is before this decline sets in, and the more they exercise afterward, the longer they can postpone, or potentially even prevent, any restriction to their independent life.

Several factors contribute to this observed drop in performance after age 35. Brad Wilkins, PhD, assistant professor of human physiology and Director of the Oregon Performance Research Laboratory at the University of Oregon, identifies muscle wasting as a major culprit, particularly if muscles are not regularly engaged. Shane Davis, MD, a non-operative sports medicine physician at Tufts Medical Center, adds that this loss of muscle mass directly impacts an individual’s strength and endurance. Dr. Westerståhl also suggests an “inherent biological aging process” that influences the signaling between nerves and muscles, which can gradually reduce overall physical responsiveness over time.

Despite these findings, experts are keen to emphasize that a decline in fitness after age 35 is not an inevitable or insurmountable fate. Dr. Wilkins asserts that both the absolute height of one’s fitness peak and the pace of its eventual decline appear to be modifiable. While consistent training is undeniably important, Dr. Wilkins suggests that individuals can actively improve or maintain their fitness into older age by strategically tweaking their routines. He notes that with age often comes increased wisdom, allowing for optimized training methods tailored to specific responses. Additionally, improvements in decision-making regarding aspects like nutrition and sleep can significantly contribute to mitigating performance decline.

Dr. Westerståhl corroborates this optimistic outlook, highlighting that study participants who were physically active—whether they maintained activity from youth or adopted it later in life—exhibited a capacity 5 to 10 percent higher than their inactive counterparts. Such consistent activity, she explains, can enable an individual to perform comparably to someone up to five years younger. Dr. Davis further reinforces this, stating that muscle mass, strength, and endurance are qualities that can be continually built throughout one’s life. He assures that regular exercise effectively slows down the typical declines associated with normal aging, making it possible for people to improve their current fitness levels and sustain good physical condition, even if reaching the absolute peak performance of their 20s might no longer be feasible.

To support sustained physical activity and maximize its benefits, Dr. Westerståhl also recommends a holistic approach encompassing the maintenance of a healthy weight, adherence to a good diet, and ensuring sufficient sleep. She stresses that "good overall health will support your ability to be active and to benefit from exercise." The collective advice from these experts is clear: continue to challenge yourself, as the capacity for achievement and improved well-being, even as one ages, can be remarkably surprising.