The relationship between age related changes in strength and fitness with body size, shape and composition

Handgrip strength (HGS), cardiorespiratory fitness (CRF) and body size, shape, and composition are all related to cardiometabolic health and are associated in cross-sectional settings. Their longitudinal relationship is less clear. We used observational data from the Study of Health in Pomerania at baseline (SHIP-TREND-0; 2008-2012) and follow-up (SHIP-TREND-1; 2016-2019) with 1,214 men and 1,293 women. HGS was measured with a hand dynamometer. CRF was assessed using cardiopulmonary exercise testing. Linear regression models were adjusted appropriately. Several sensitivity analyses were performed. From baseline to follow-up (7 years) HGS decreased in men (3.5 kg) and women (0.8 kg). VO₂peak lessened in men (36 ml/min) and increased in women (53 ml/min). We only found significant relations in men where a 1 l decline in VO₂peak was associated with a 0.87 kg larger decrease in fat free mass and with a 1.15 kg stronger decline in body weight. All other analysis revealed non-significant findings. This longitudinal analysis suggests that age related changes in strength and CRF are not related to body size and shape but only composition (in men). A novelty of our findings are the sex-specific aspects given that strength decreased much stronger in men compared to women.