Age‐dependent variations in the directional sensitivity of balance corrections and compensatory arm movements in man

Abstract

We investigated the effects of ageing on balance corrections induced by sudden stance perturbations in different directions. Effects were examined in biomechanical and electromyographic (EMG) recordings from a total of 36 healthy subjects divided equally into three age groups (20-34, 35-55 and 60-75 years old). Perturbations consisted of six combinations of support-surface roll (laterally) and pitch (forward-backward) each with 7.5 deg amplitude (2 pure pitch, and 4 roll and pitch) delivered randomly. To reduce stimulus predictability further and to investigate scaling effects, perturbations were at either 30 or 60 deg s _1 . In the legs, trunk and arms we observed age-related changes in balance corrections. The changes that appeared in the lower leg responses included smaller stretch reflexes in soleus and larger reflexes in tibialis anterior of the elderly compared with the young. For all perturbation directions, onsets of balance correcting responses in these ankle muscles were delayed by 20-30 ms and initially had smaller amplitudes (between 120-220 ms) in the elderly. This reduced early activity was compensated by increased lower leg activity after 240 ms. These EMG changes were paralleled by comparable differences in ankle torque responses, which were initially (after 160 ms) smaller in the elderly, but subsequently greater (after 280 ms). Findings in the middle-aged group were generally intermediate between the young and the elderly groups. Comparable results were obtained for the two different stimulus velocities. Stimulus-induced trunk roll, but not trunk pitch, changed dramatically with increasing age. Young subjects responded with early large roll movements of the trunk in the opposite direction to platform roll. A similarly directed but reduced amplitude of trunk roll was observed in the middle-aged. The elderly had very little initial roll modulation and also had smaller stretch reflexes in paraspinals. Balance-correcting responses (over 120-220 ms) in gluteus medius and paraspinals were equally well tuned to roll in the elderly, as in the young, but were reduced in amplitude. Onset latencies were delayed with age in gluteus medius muscles. Following the onset of trunk and hip balance corrections, trunk roll was in the same direction as support-surface motion for all age groups and resulted in overall trunk roll towards the fall side in the elderly, but not in the young. Protective arm movements also changed with age. Initial arm roll movements were largest in the young, smaller in the middle aged, and smallest in the elderly. Initial arm roll movements were in the same direction as initial trunk motion in the young and middle aged. Thus initial roll arm movements in the elderly were directed oppositely to those in the young. Initial pitch motion of the arms was similar across age groups. Subsequent arm movements were related to the amplitude of deltoid muscle responses which commenced at 100 ms in the young and 20-30 ms later in the elderly. These deltoid muscle responses preceded additional arm ro...

The influence of artificially increased hip and trunk stiffness on balance control in man

“…Recently, however, this concept has been challenged for motion occurring during quiet stance (Aramaki et al 2001;Loram and Lakie 2002). Indeed, as body motion increases in amplitude and direction from that of quiet standing (Fitzpatrick et al 1992(Fitzpatrick et al , 1994Winter et al 1996Winter et al , 1998Gatev et al 1999;Accorneo et al 1997), to that induced by a support surface perturbation in the pitch plane alone (Cordo and Nashner 1982;Allum et al 1993;Horak et al 1997), and finally to that induced by combined roll and pitch plane perturbations (Moore et al 1988;Maki et al 1994aMaki et al , 1994bHenry et al 1998b;Carpenter et al 1999;Allum et al 2002), the multi-link nature of human postural corrections becomes increasingly prominent. This multi-link strategy involves hinging at the knees, hips and lower vertebral column, in addition to ankle joint motion .…”

“…Our second goal was to clarify the pathophysiology of trunk stiffness which we suggested helps cause impaired balance control with ageing and in neurological disorders, including Parkinson's disease and severe proprioceptive loss (Carpenter et al 2004;Allum et al 2002;Bloem et al 2002). In all these groups, changes in trunk roll motion were noted as early as 50 ms after a postural perturbation, suggesting that active stiffening prior to the perturbationrather than inappropriate active postural reactions-was mainly responsible for the loss of trunk flexibility.…”

The use of peripheral vision to guide perturbation-evoked reach-to-grasp balance-recovery reactions

“…Historically, studies of balance-recovery reactions have tended to focus primarily on the lower limbs; however, there is an increasing awareness that rapid movements of the upper limbs also play an important role in stabilizing the body, both in daily life McIlroy 1996, 1997;Rabinovitch et al 2009) and in experimental settings (Romick-Allen and Schultz 1988;McIlroy and Maki 1995b;Maki and McIlroy 1997;Tang et al 1998;Allum et al 2002;Marigold and Patla 2002;Marigold et al 2003;Misiaszek 2003;Cham and Sandrian 2007;Roos et al 2008;Pijnappels et al 2010). In the event that attempts to recover balance are unsuccessful, arm reactions may also act to help absorb the energy of the fall and protect against head injury (Roberts 1978) or hip fracture (Feldman and Robinovitch 2007).…”

“…Even small balance perturbations can evoke arm reactions, particularly when the perturbation is novel or unexpected (Maki and Whitelaw 1993;Corbeil et al 2004), and it has been proposed that the arm movements can help to stabilize the body through various 'counter-balancing' inertial or gravitational mechanisms (Romick-Allen and Schultz 1988; Allum et al 2002;Marigold and Patla 2002;Marigold et al 2003;Misiaszek 2003;Hoff 2007;Marigold and Misiaszek 2009;Roos et al 2008;Pijnappels et al 2010).…”

Visuomotor behaviors in computer-based reaching tasks by young and older adults: implication for geriatric rehabilitation

“…Previous studies indicated that ageing-related deterioration undermines daily life activities of older adults in different aspects. Older adults are more vulnerable than young adults with decreased visuospatial working memory [1,2], deteriorated cognitive processes [3,4], increased movement variability and instability [5], decreased directional sensitivity of balance [6] and decreased muscle strength [7]. Ageing creates differences in neural control of movement within different brain regions, such as the prefrontal cortex and basal ganglia, which in turn affects motor performance [8].…”