A massive Swedish study that tracked people for nearly five decades has uncovered a striking reality about aging and physical performance. Researchers found that fitness, strength, and muscle endurance begin declining around age 35. But the findings also deliver an encouraging message: becoming active later in life can still significantly improve physical ability. The research was conducted at Karolinska Institutet as part of the Swedish Physical Activity and Fitness study (SPAF). Scientists followed several hundred randomly selected men and women in Sweden from ages 16 to 63, repeatedly measuring their fitness and strength over a span of 47 years. The study was published in the Journal of Cachexia, Sarcopenia and Muscle. Rare Long Term Fitness Data Most previous studies on aging and physical performance relied on cross sectional comparisons between different age groups.…