Does muscular weakness account for younger children's enhanced force variability?

Abstract

This study examined the degree to which younger children's greater variability in force control is associated with muscular weakness. Children aged 6, 8, and 10 years and adults aged 18-22 years produced isometric force via index finger metacarpo-phalangeal joint flexion to varying force levels (5%, 15%, 25%, and 35% maximal voluntary contraction). The force output of the younger children was more variable and had greater time dependent structure compared to that of the adults at all force levels. However, the effect of age on variability was significantly reduced, but not eliminated when absolute muscular strength was taken into account. It is concluded that age-related changes in children's force control result from a multitude of developmental processes including increases in muscular strength.

Oral and Manual Force Control in Preschool-Aged Children: Is There Evidence for Common Control?

“…In contrast, precision-and power-grip strengths increase in a step-like fashion, sometimes synchronously (i.e., power and precision change similarly) and sometimes asynchronously (i.e., power may change but precision may not). This discontinuity in development reflects the dynamic interplay of maturation and experience affecting biological development (Sosnoff, Deutsch, & Newell, 2007), as well as cognitive-strategic development (i.e., using feedforward strategies for improved coordination; Lazarus et al, 1995;Potter et al, 2006). There is a large range in the maximum tongue strength of TD preschool children, with some of the children in the 3,0 age group performing at or above the mean of the children in the 4,6-5,0 age group and some of the children in the 4,6-5,0 age group performing at or below the mean of the children in the 3,0 age group.…”

“…The difference in performance among the hands, fingers, and tongue may be explained, in part, by experience, which influences biological and cognitive-strategic development (Sosnoff et al, 2007). Because a whole hand grip is used for early grasping, young children have had the most experience using their power grip and this hand formation produced the smallest overshoot.…”

Approximate entropy based on attempted steady isometric contractions with the ankle dorsal- and plantarflexors: Reliability and optimal sampling frequency

“…High values of ApEn correspond to low system regularity and the other way around (Pincus, 1991). ApEn has been the preferred method to quantify motor-system regularity, when evaluated as torque time-series from attempted steady isometric contractions (Slifkin and Newell, 1999;Deutsch and Newell, 2004;Sosnoff et al, , 2007. Furthermore, ApEn values calculated for force time-series from attempted steady isometric index finger-thumb grip seem to correlate with the severity of Parkinson's disease (Vaillancourt et al, 2001).…”

“…The parameter N was 255 or 850 observations, respectively (explained below), which is sufficient for ApEn analyses (Pincus and Goldberger, 1994). Traditionally, when ApEn has been calculated from attempted steady isometric contractions, the torque time-series have been down-sampled to 100 Hz (Slifkin and Newell, 1999;Vaillancourt and Newell, 2003;Jordan and Newell, 2004;Deutsch and Newell, 2004;Sosnoff et al, 2007). In order to compare the optimized and the traditionally used sampling frequency, torque time-series were down-sampled to 30 and 100 Hz.…”