Relationship between muscle-strengthening activities recommended by physical activity guidelines and knee extensor strength in the elderly

[Purpose] This study aimed to cross-sectionally examine the relationship between the practice of muscle-strengthening activities assessed according to Japanese and foreign physical activity guidelines and knee extensor strength in the elderly. [Participants and Methods] Overall, 223 (66 males and 157 females) participants aged ≥60 years were included. The questionnaire included four items on muscle-strengthening activities: undergoing strength training, performing vigorous farming and gardening, carrying heavy loads, and climbing stairs and hills. Thereafter, participant performance was classified as “sufficient” or “insufficient” based on whether they practiced each muscle-strengthening activity for ≥2 or <2 days a week, respectively. [Results] After the adjustment for age, gender, body mass index, physical activity level, and the practice of other muscle-strengthening activities, knee extensor strength was significantly higher in the elderly participants who sufficiently practiced strength training than in those who did not. Furthermore, those who sufficiently practiced farming and gardening had significantly higher knee extensor strength than those who did not. [Conclusion] Our findings suggest that the non-exercise muscle-strengthening activity of sufficient farming and gardening practiced according to physical activity guidelines is positively associated with knee extensor strength independent of other muscle-strengthening activities or the amount of physical activity in healthy elderly individuals.