The Relationship Between Force and Force Variability in Minimal and Near-Maximal Static and Dynamic Contractions

Abstract

The critical assumption of linearity between force and force variability for rapid movements made by Schmidt, Zelaznik, and Frank (1978) was studied in four experiments in the present study. The first three experiments extended earlier work showing linearity between force and force variability for submaximal force levels in static and dynamic contractions. However, at near-maximal force levels, when force was increased, force variability leveled off and then decreased in both static and dynamic conditions. A fourth experiment using the rapid-timing paradigm showed that increased submaximal loads on the movement produced slight decreases in VE. But when the loads were larger, where force and force variability were no longer linearly related, increased load led to larger decreases in VE. These observations led to the hypothesis that VE is linearly related to the ratio of force variability to force; data from two experiments are presented that support this idea. The motor-output variability theory seems to hold for a wide range of sub-maximal force values, but needs modification for those conditions where near-maximal forces are required.

A kinematic theory of rapid human movements: Part III. Kinetic outcomes

“…6a and c, is a commonly accepted fact, both in isometric and in isotonic studies. This fundamental phenomenon has been reported for peak velocity (Gielen et al 1985;Nagasaki 1989), peak acceleration (Carlton and Newell 1988; Gielen et al 1985), peak isotonic force (Carlton and Newell 1988), peak isometric force Sherwood and Schmidt 1980), peak first and second time derivative of the isometric force ) and peak torque (Carlton and Newell 1988). Such general behavior is not surprising in the context of the kinematic theory since it is always the same neuromuscular synergy that is investigated and since a single basic law (1) is sufficient to describe its general behavior under a number of conditions.…”

Kinematic description of variability of fast movements: analytical and experimental approaches

“…An increase in positional variability during movements performed as fast as possible with an increase in movement distance has been described in many studies and is considered an example of the speed-accuracy trade-off (Schmidt et al 1978(Schmidt et al , 1979Sherwood and Schmidt 1980;Wright and Meyer 1983; although see Latash and Gottlieb 1990). In all these studies, positional variability was assessed at the alleged time of movement termination.…”

“…However, such a dependence still exists at later times as well. Let us note that in many studies, movements were considered stopped and measurements were made at a moment of touching the target (Schmidt et al 1978(Schmidt et al , 1979Sherwood and Schmidt 1980;Sherwood et al 1988). The velocity of the endpoint at the moment of impact was presumably not zero.…”

Distance versus position information in the control of aiming movements

“…(Below, we shall argue that, even at this level, Plamondon & Alimi's [P&A's] account is flawed). The level of movement execution can contribute to other types of trade-offs, for example to the scaling of the standard deviation of final position with movement distance and time (Schmidt et al 1979;Sherwood & Schmidt 1980). Thus, P&A's account fails to distinguish between these distinct forms of trade-offs and analyzes them erroneously as a single phenomenon.…”

“…Most of the detailed studies have reported nonproportional relationships between force and force variability in both isometric (Carlton & Newell 1985;Fullerton & Cattell 1892;Jenkins 1947;Newell & Carlton 1985;Noble & Bahrick 1956;Provins 1957) and anisometric tasks (Newell et al 1982). Furthermore, this relationship was found to have an inverted U shape Sherwood & Schmidt 1980;Sherwood et al 1988).…”