TY - JOUR
T1 - Postural synergies associated with a stepping task
AU - Mercer, Vicki Stemmons
AU - Sahrmann, Shirley A.
PY - 1999
Y1 - 1999
N2 - Background and Purpose. Synergistic relationships among multiple muscle components are thought to exist to simplify control of posture and movement. The purpose of this study was to examine the extent to which children, young adults, and older adults exhibit consistent sequences of postural muscle activation when lifting the right foot onto a step from a standing position. Subjects. Twenty subjects without known impairments of the neuromuscular system (10 male, 10 female) in each of 3 age groups - children (8-12 years), young adults (25-35 years), and older adults (65-73 years) - participated. Methods. A pressure switch taped to the subject's right foot was used to determine movement onset and offset. Latencies of muscle activation were determined using surface electromyography. A preferred postural synergy was defined as the sequence of postural muscle activation observed during the majority of trials for each subject. Results. Mean movement times did not differ among age groups. Although the left tibialis anterior (TA) muscle was the first of the postural muscles activated in 93% of the trials, subjects displayed considerable variability in the subsequent order of postural muscle activation. Across subjects, a total of 14 different preferred postural synergies were observed. Age groups did not differ in the number of different synergies. Conclusion and Discussion. Early TA activation may reflect biomechanical constraints of the stepping task, producing forward displacement of the center of mass over the changing base of support. The fact that subjects of all ages were quite variable in the specific sequences of muscles activated subsequent to the TA suggests that, for this type of task, therapists should not focus their interventions on facilitating execution of particular synergy patterns.
AB - Background and Purpose. Synergistic relationships among multiple muscle components are thought to exist to simplify control of posture and movement. The purpose of this study was to examine the extent to which children, young adults, and older adults exhibit consistent sequences of postural muscle activation when lifting the right foot onto a step from a standing position. Subjects. Twenty subjects without known impairments of the neuromuscular system (10 male, 10 female) in each of 3 age groups - children (8-12 years), young adults (25-35 years), and older adults (65-73 years) - participated. Methods. A pressure switch taped to the subject's right foot was used to determine movement onset and offset. Latencies of muscle activation were determined using surface electromyography. A preferred postural synergy was defined as the sequence of postural muscle activation observed during the majority of trials for each subject. Results. Mean movement times did not differ among age groups. Although the left tibialis anterior (TA) muscle was the first of the postural muscles activated in 93% of the trials, subjects displayed considerable variability in the subsequent order of postural muscle activation. Across subjects, a total of 14 different preferred postural synergies were observed. Age groups did not differ in the number of different synergies. Conclusion and Discussion. Early TA activation may reflect biomechanical constraints of the stepping task, producing forward displacement of the center of mass over the changing base of support. The fact that subjects of all ages were quite variable in the specific sequences of muscles activated subsequent to the TA suggests that, for this type of task, therapists should not focus their interventions on facilitating execution of particular synergy patterns.
KW - Electromyography
KW - Physical therapy
KW - Stepping
KW - Synergy
UR - http://www.scopus.com/inward/record.url?scp=0033460313&partnerID=8YFLogxK
U2 - 10.1093/ptj/79.12.1142
DO - 10.1093/ptj/79.12.1142
M3 - Article
C2 - 10630283
AN - SCOPUS:0033460313
SN - 0031-9023
VL - 79
SP - 1142
EP - 1152
JO - Physical Therapy
JF - Physical Therapy
IS - 12
ER -