Acute Responses to Resistance Training on Body Composition, Muscular Fitness and Flexibility by Sex and Age in Healthy War Veterans Aged 50–80 Years

Background: Although evidence suggests that resistance training should be prescribed as a method to enhance or maintain physical fitness, these findings are mostly based on research on younger men. Studies investigating responses by sex and age to resistance training, especially in war veterans aged ≥50 years, are lacking. Therefore, the main purpose of this study was to examine whether a 4-week resistance training program would have similar effects on body composition, muscular fitness, and flexibility in men and women aged 50–80 years. Methods: Seven-hundred and sixty-four participants were recruited and categorized into two groups each of men and women aged 50–64 and 65–80 years. The training intervention lasted 4 weeks and consisted of three 60 min sessions per week. All participants were tested for each of the following physical fitness components: body composition, push-ups in 30 s, chair-stands in 30 s, sit-ups in 30 s, and a sit-and-reach test. Results: Over the intervention period of 4 weeks, body weight (p = 0.002) and the percent of fat mass (p < 0.001) decreased, while the percent of lean mass (p < 0.001) in push-ups in 30 s (p < 0.001), chair-stands in 30 s (p < 0.001), sit-ups in 30 s (p < 0.001), and sit-and-reach (p < 0.001) increased. Significant time*age interactions were shown for push-ups in 30 s (F(1,763) = 4.348, p = 0.038) and chair-stands in 30 s (F(1,763) = 9.552, p = 0.002), where men and women aged 50–64 years exhibited larger time-induced changes compared to their older (65–80 yr) counterparts. Effect sizes were similar between sex- and age-specific groups. Conclusions: The 4-week resistance training produced similar pronounced positive effects on body composition, muscular fitness, and flexibility, while men and women aged 50–64 years displayed significantly larger improvements in upper and lower muscular fitness compared with their 65–80-year-old counterparts.