Gross motor skills have traditionally referred to motor activities that move the body through the environment or use the large muscles of the torso, arms, and legs to transport or displace an object in some way. By contrast, fine motor skills have typically been described as involving the arms, hands, and fingers in acts of manipulation. For example, psychometric assessments of gross motor skills include balance, crawling, walking, running, jumping, climbing, and hopping, but may also include throwing or other ball handling or hitting activities. However, this distinction has more recently been recast with respect to the underlying dynamics of the behavior and the ecological fit between dynamics and the information available to the actor.
A dynamical systems perspective on motor development provides a set of fundamental principles for characterizing gross and fine motor skills in terms of action systems. These are very general functional classes of behavior that have evolved in response to particular environmental pressures. The focus here is on three action systems: basic orienting (maintaining a functional orientation to gravity and to the surfaces and media of the environment), locomoting (moving from place to place by using disequilibrium to initiate motion), and performatory acts that displace objects by producing large forces or contain objects that approach the body with large forces. The development of these three action systems throughout the life span is proposed as the underlying basis for the observation of age-related improvements in the traditional gross motor skills of balance, locomotion, and physically displacing objects. Exceptionally skilled performance by adults during performatory acts, such as juggling, reveals clues about the fundamental principles of coordination. Moreover, the problems of balance experienced by aging adults illustrate the relation between basic orienting and other skills, especially locomoting.
All of the action systems consist of several functionally specific components of orienting: obtaining a relatively persistent orientation to the environment, supporting the body’s weight, balancing forces acting on the body and limbs, and keeping the perceptual systems attuned to available information. These components of orienting are clearly at play in the development of sitting and standing during the first year, skills that require control of destabilizing forces acting on the body. There are two notable trends in the development of sitting and standing. First, achievement of postural stability makes it possible to anticipate and counteract muscular forces. During sitting, for example, coordinated activation of the extensors and flexors of the trunk and hips allows the infant to control upper body sway. With improved trunk balance, there is a narrowing of the base of support as the legs are brought together and extended at the knees. Similarly, during standing, infants learn to control rotations about the ankles by applying torques (rotational forces) at the joint. Second, the achievement of postural control opens up new possibilities for perceptually exploring the body’s capabilities, such as manipulating objects with hands freed from the task of support.
The locomotor action system builds on this foundation of basic orienting: between 15 and 18 months, standing infants allow the body to sway forward in order to initiate walking. Force plate measurements demonstrate that once infant walkers reach a steady state velocity, their step-cycle organization is virtually identical to that of mature walkers. The step cycle consists of four phases. Swing phase (toe-off to heel-strike) is divided into F(lexion) and E(xtension) phases. The F begins at toe-off and ends as knee extension begins during swing. The E1 phase begins at knee extension and ends at heel-strike. The stance phase (from heel-strike to toe-off) consists of E2 and E3 phases. The postural instability that promotes a transition from stance to walking is also apparent in the developmental transitions in coordination of gait. Detailed longitudinal kinematic analyses indicate that for newly walking infants, intralimb coordination of shank and thigh motion is unstable, but attracted to a consistent phase angle. By 18 months, a reciprocal arm swing and heel-strike are present. Mature gait, as assessed by single limb stance duration, step length, ratio of pelvic to step width, and progression velocity is well established by age 3. Walking velocity and stride length increase throughout childhood, and stride width is becoming narrower.
When the step cycle is placed in the context of its ground support, it becomes apparent that the muscles do not supply all of the forces used for locomoting. When a pulling or pushing force stretches a material (such as biological tissue), the energy stored in the material will provide potential energy for an elastic force that tends to return the material to its original state. Infants younger than 1 year of age will learn to harness the elastic forces stored in a spring as they bounce vertically. Walking proficiency improves in toddlers as step frequency and length, head and trunk stability, amplitude of hip flexion, and coordination of lower limb movements reflect a dynamic integration of postural equilibrium and forward propulsion. During running, both gravitational potential energy and forward kinetic energy reach a minimum in the support phase, and both go through a maximum as the body takes off and flies through the air. Once toddlers begin to run, they may begin to harness the elastic potential energy at particular moments in the step cycle.
Developmental levels of hopping and jumping illustrate how further improvement in the child’s ability to harness properties of the body and its relation to gravity enable them to safely use greater forces to propel the body away from support surfaces. During hopping, each of the four limbs, which characteristically behave like harmonic oscillatory systems, appears to become mutually entrained so that they act as a single “spring.” Developmental changes are attributed to changes in the dynamics of the system. For example, in developmental level 2, called fall and catch, forward lean allows the body to fall forward of the support foot, the swing leg is inactive, and balance is recovered in the landing. Here, the force of landing on the support foot is quite high. In level 3, called projected takeoff, the swing leg pumps up and down to assist in takeoff. The basis for the developmental transition is a change in a dynamical parameter of the body, namely, stiffness. Rather than continuing a jarring, potentially injurious manner of hopping, the body reorganizes its movement, lowering the stiffness setting in the landing leg (perhaps through central regulation of the stretch reflex).
Jumping is another means of using the considerable force production of the body to escape the pull of gravity. It is used throughout the life span for projecting the body into the air in a way that achieves a wide range of skilled performance, including dance and athletics. Descriptively, jumping develops by increasingly taking advantage of the propulsive power of the shoulders and arms. The youngest children use no arm action, and leg action is usually a one-foot takeoff. Next, there is some shoulder flexion, but the arms remain immobile. Finally, children use shoulder flexion at the time of takeoff to achieve a complete and efficient arm action. Interestingly, even though position and magnitude measurements of the lower extremities change between the ages of 3 and 9 years, delay in peak extension velocity for hip, knee, and ankle remains highly consistent. This suggests that the support aspect of the jump that maintains orientation to the ground remains stable and that developing the capacity for propulsion of the body into the air is a process of introducing disequilibrium against a background of postural stability.
Actions On Objects
The performatory act of propelling an object by means of perceptually guided release or brief contact with parts of the body (e.g., throwing, hitting, or kicking a ball) requires postural support on the ground that can withstand changing disequilibrating forces. Children may first begin to push a ball from a seated position, but once they have gained standing stability during the toddler period, rudimentary throwing patterns appear. The developmental pattern is one in which there is a rapid transfer of support in muscle groups so that a flowing sequence of muscular action produces propulsive force at a single point of contact with the ball. Throughout childhood and into adulthood, throwing velocity and accuracy increases, and individual differences in skill become apparent in games involving throwing, hitting, or kicking a ball. Early skilled performance in using the two hands, as in clapping, and expertise in coordinative skills, such as juggling, may have an underlying basis in the ability to detect regions of stability in dynamics and to time actions of upper body so that they are only intermittently stable. Coordination on the “edge” of stability in the phase relation of both hands introduces a degree of flexibility to adapt to the even tiny fluctuations inevitable in each catch and throw.
The dynamics of movement relative to balance and postural support is also the basis for age-related declines in walking performance by older adults. Beyond about age 60, walking velocity decreases, there is less vertical excursion of the center of gravity, and disturbed coordination exists between upper and lower extremities. During the seventh and eight decades, there is often a further loss of the normal arm–leg synergy, an overproduction of “unwanted” movements, and diminished flexion in the swing phase. At the approach of the century mark, there may be rapid disintegration of the gait pattern, arrhythmia in step rate, and absence of any arm swing movement. The similarities between motor patterns in early childhood and senescence, respectively, suggest that both periods in development experience instability in postural equilibrium. In the former case, such disequilibrium comes to be used in the service of development of new motor skills. It remains to be determined whether advances in 21st century technology will assist older adults in preventing such disequilibria from becoming incapacitating.
- Assaiante, , & Amblard, B. (1995). An ontogenetic model for the sensorimotor organization of balance control in humans. Human Movement Science, 14, 13–43.
- Bardy, G., Oullier, O., Bootsma, R. J., & Stoffregen, T. A. (2002). Dynamics of human postural transitions. Journal of Experimental Psychology: Human Perception and Performance, 28, 499–514.
- Beek, P. , & Van Santvoord, A. M. (1996). Dexterity in cascade juggling. In M. Latash & M. T. Turvey (Eds.), Dexterity and its development (pp. 377–391). Mahwah, NJ: Erlbaum.
- Bertenthal, B. I., & Clifton, R. K. (1998). Perception and action. In D. Kuhn & R. Siegler (Eds.), Handbook of child psychology, V 2: Cognition, perception, and language (pp. 51–102). New York: Wiley.
- Breniere, Y., Bril, , & Fontaine, R. (1989). Analysis of the transition from upright stance to steady state locomotion in children with under 200 days of autonomous walking. Journal of Motor Behavior, 21, 20–37.
- Cheron, , Bouillot, E., Dan, B., Bengoetxea, A., Draye, J., & Lacquaniti, F. (2001). Development of a kinematic coordination pattern in toddler locomotion: Planar covariation. Experimental Brain Research, 137, 455–466.
- Clark, E., & Phillips, S. J. (1987). The step cycle organization of infant walkers. Journal of Motor Behavior, 19,421–433.
- Clark, J. , Phillips, S. J., & Petersen, R. (1989). Developmental stability in jumping. Developmental Psychology, 25, 929–935.
- Clark, E., Truly, T. L., & Phillips, S. J. (1990). A dynamical systems approach to understanding the development of lower limb coordination in locomotion. In H. Bloch & B. Bertenthal (Eds.), Sensory-motor organizations and development in infancy and early childhood (pp. 363–378). Amsterdam: Kluwer.
- Craik, R. (1989). Changes in locomotion in the aging adult. In M. Woollacott & A. Shumway-Cook (Eds.), The development of posture and gait across the lifespan (pp. 176–201). Columbia: University of South Carolina
- Cratty, B. J. (1986). Perceptual and motor development in infants and childr Englewood Cliffs, NJ: Prentice-Hall.
- Fitzpatrick, P., Schmidt, C., & Lockman, J. J. (1996). Dynamical patterns in the development of clapping. Child Development, 67, 2691–2708.
- Forssberg, , Stokes, V., & Hirschfeld, H. (1992). Basic mechanisms of human locomotor development. In M. Gunnar & C. Nelson (Eds.), Developmental behavioral neuroscience (Minnesota Symposia on Child Psychology, Vol. 24, pp. 37–73). Hillsdale, NJ: Erlbaum.
- Gabell, , & Nayak, U. (1984). The effect of age on variability in gait. Journal of Gerontology, 39, 662–666.
- Getchell, , & Roberton, M. A. (1989). Whole body stiffness as a function of developmental level in children’s hopping. Developmental Psychology, 25, 920–928.
- Goldfield, E. C. (1995). Emergent forms: Origins and early development of human action and per New York: Oxford University Press.
- Goldfield, C., Kay, B., & Warren, W. H., Jr. (1993). Infant bouncing: The assembly and tuning of action systems. Child Development, 64, 1128–1142.
- Halverson, L. , Roberton, M. A., Langendorfer, S., & Williams, K. (1979). Longitudinal changes in children’s overarm throw ball velocities. Research Quarterly, 50, 256–264.
- Humphrey, J. H. (1992). Motor learning in childhood education. Springfield, IL:
- Kelso, A. S., & DeGuzman, G. C. (1992). The intermittent dynamics of coordination. In G. E. Stelmach & J. Requin (Eds.), Tutorials in motor behavior II (pp. 549–561). Amsterdam: Elsevier.
- Li, , van den Bogert, E., Caldwell, G. E., van Emmerik, R., & Hamill, J. (1999). Coordination patterns of walking and running at similar speed and stride frequency. Human Movement Science, 18, 67–85.
- Lockman, J., & Thelen, E. (1993). Developmental biodynamics: Brain, body, behavior connections. Child Development, 64, 953–959.
- Ozkaya, N., & Nordin, M. (1999). Fundamentals of biomec New York: Springer-Verlag.
- Pick, L., Jr. (1989). Motor development: The control of action. Developmental Psychology, 25, 867–870.
- Reed, S. (1988). Applying the theory of action systems to the study of motor skills. In O. G. Meijer & K. Roth (Eds.), Complex movement behavior: The motor-action controversy (pp. 339–380). Amsterdam: Elsevier.
- Thelen, E., & Smith, L. B. (1994). A dynamic systems approach to the development of cognition and action. Cambridge: MIT
- Thelen, , & Ulrich, B. (1991). Hidden skills. Monographs of the Society for Research in Child Development, 56 (No.1, Serial No. 223). Chicago: University of Chicago Press.
- Woollacott, M. , & Jensen, J. L. (1996). Posture and locomotion. In H. Heuer & S. Keele (Eds.), Handbook of perception and action (Vol. 2, pp. 333–403). London: Academic Press.