Can age affect the importance of propulsion onset for jump performance?

To determine if stretch shortening cycle potentiation of the lower extremity joints, specifically at the propulsion onset, is related to countermovement (CMJ) jump height (JHt) and enhancement of JHt in older vs young adults. Cross-Sectional Study. University Laboratory. Community-dwelling older adults and young adults (n=22, Older/young adults= 10/12. None. All the following outcome measures were collected for CMJ and static jump (SJ). JHt was calculated directly from the greater trochanter marker data as the highest value achieved during jump - standing upright height. Propulsion onset was calculated as the first positive data point (after the eccentric phase) of the joint angular velocity for each respective joint (hip, knee, and ankle). Joint extensor moments at the propulsion onset were calculated as the percentage of the peak extensor moment for each respective joint for each jump condition (CMJ and SJ). All the joint extensor moments were normalized for body weight. Ratios of (1) JHt (JH) and (2) respective joint-specific extensor moments for CMJ/SJ were calculated as surrogate markers of potentiation at the propulsion onset. All participants demonstrated JHt potentiation (p< 0.05) with 14% lower JHt potentiation in older adults (p< 0.05). All participants demonstrated extensor moment potentiation at all joints (p< 0.001 for both). Further, extensor moment potentiation of the ankle was greater than knee and hip (p< 0.01 for both). Similarly, extensor moment potentiation of the ankle was greater or tended to be greater than knee (p=0.044) and hip (p=0.051) in young adults. We noted positive relationships between extensor moment potentiation of the knee (r=0.758, p=0.011) and hip (rspearman=0.817, p=0.007) with CMJ JHt in older adults only. JHt potentiation (CMJ/SJ) showed a trend towards positive relationship with the knee moment potentiation (r=0.627, p=0.052) in older adults only. CMJ JHt and JHt potentiation are dictated, in part, by the hip and knee extensor moment potentiation in older adults. Thus, we posit that the propulsion onset is a critical event that can influence jump performance in older adults. None. [ABSTRACT FROM AUTHOR]