Age-related differences in adaptation during childhood: the influences of muscular power production and segmental energy flow caused by muscles

Abstract

Acquisition of skillfulness is not only characterized by a task-appropriate application of muscular forces but also by the ability to adapt performance to changing task demands. Previous research suggests that there is a different developmental schedule for adaptation at the kinematic compared to the neuro-muscular level. The purpose of this study was to determine how age-related differences in neuro-muscular organization affect the mechanical construction of pedaling at different levels of the task.By quantifying the flow of segmental energy caused by muscles, we determined the muscular synergies that construct the movement outcome across movement speeds. Younger children (5-7 years; n=11), older children (8-10 years; n=8), and adults (22-31 years; n=8) rode a stationary ergometer at 5 discrete cadences (60 rpm, 75 rpm, 90 rpm, 105 rpm, and 120 rpm). at 10% of their individually predicted peak power output. Using a forward dynamics simulation, we determined the muscular contributions to crank power, as well as muscular power delivered to the crank directly and indirectly (through energy absorption) during the downstroke and the upstroke of the crank cycle.We found significant Age x Cadence interactions for − peak muscular power at the hip joint (Wilks' Lambda=.441, F(8,42)=2.65, p=.019) indicating that at high movement speeds children produced less peak power at the hip than adults − muscular power delivered to the crank during the downstroke and the upstroke of the crank cycle (Wilks' Lambda=.399, F(8,42)=3.07, p=.009) indicating that children delivered a greater proportion of the power to the crank during the upstroke when compared to adults. − hip power contribution to limb power Wilks' Lambda=.454, F(8,42)=2.54, p=.023) indicating a cadence-dependence of age-related differences in the muscular synergy between hip extensors and plantarflexors.The results demonstrate that in spite of a successful performance, children construct the task of pedaling differently when compared to adults, especially when they are pushed to their performance limits. The weaker synergy between hip extensors and plantarflexors suggests that a lack of inter-muscular coordination, rather than muscular power production per-se, is a factor that limits children's performance ranges.3

Muscular and non-muscular contributions to maximum power cycling in children and adults: implications for developmental motor control

“…Van Praagh and Doré speculated that the ability to coordinate synergistic and antagonistic muscle groups in a timely fashion could contribute to age-related differences in maximum power production . This speculation is supported the finding by Korff and Jensen that children demonstrated weaker intermuscular synergies in terms of segmental energy transfer between the synergistic muscle groups of the lower limb during submaximal cycling (Korff and Jensen, 2007).…”

“…Therefore, one might have expected that age-related differences in overall maximum power production could be due to the children's lack of ability to produce power at the individual joints of the lower limbs. This speculation is substantiated by findings from Korff and Jensen, who showed that during submaximal cycling children's relative maximum power at the hip joint was less than that of adults (Korff and Jensen, 2007). Our findings contradict this speculation as during our maximum cycling task children produced greater relative peak joint powers at both the knee and the hip joint.…”

“…The effect sizes describing the difference between children and adults were -0.20, 1.07 and 0.56 for the ankle, knee and hip joints, respectively. related differences in maximum power production are partly due to differences in intermuscular coordination, such as muscle timings or the transfer of segmental energy between synergistic muscle groups (Fregly and Zajac, 1996;Korff and Jensen, 2007). One limitation to this speculation is that in this study we did not take individual muscle contributions into account.…”

“…ankle, knee and hip power) (Broker and Gregor, 1994). Previously, we have shown that during submaximal cycling at high movement speeds, children demonstrate weaker intermuscular synergies in terms of joint power production and segmental energy flow when compared with adults (Korff and Jensen, 2007). Here, we tested the hypothesis that during maximal cycling, relative average joint power contributions to total pedal power as well as relative peak powers at the lower limb joints do not differ between children and adults.…”

“…Several authors have reported age-related differences in muscular force and power production during submaximal cycling (Brown and Jensen, 2003;Brown and Jensen, 2006;Korff and Jensen, 2007;Korff and Jensen, 2008). Brown and Jensen speculated that these differences were partly due to age-related differences in the anthropometry of the performer (Brown and Jensen, 2003).…”