Elodie Piche1, Frédéric Chorin2, Raphaël Zory3, Patricia Duarte Freitas4, Olivier Guerin5, Pauline Gerus6. 1. Université Côte d'Azur, LAMHESS, Nice, France; Université Côte d'Azur, Centre Hospitalier Universitaire de Nice, Clinique Gériatrique du Cerveau et du Mouvement, Nice, France. Electronic address: piche.e@chu-nice.fr. 2. Université Côte d'Azur, LAMHESS, Nice, France; Université Côte d'Azur, Centre Hospitalier Universitaire de Nice, Clinique Gériatrique du Cerveau et du Mouvement, Nice, France. 3. Université Côte d'Azur, LAMHESS, Nice, France; Institut universitaire de France, France. 4. Université Côte d'Azur, Centre Hospitalier Universitaire de Nice, Clinique Gériatrique du Cerveau et du Mouvement, Nice, France. 5. Université Côte d'Azur, Centre Hospitalier Universitaire de Nice, Clinique Gériatrique du Cerveau et du Mouvement, Nice, France; Université Côte d'Azur, CNRS UMR 7284/INSERM U108, Institute for Research on Cancer and Aging Nice (IRCAN), Faculté de médecine, Nice, France. 6. Université Côte d'Azur, LAMHESS, Nice, France.
Abstract
BACKGROUND: The net metabolic cost of walking (NCw) and the co-activation of leg muscles are both higher in old adults (OG) than in young adults (YG). Nevertheless, the relation between the two remains unresolved, mainly due to the controversial co-activation measurement method used in previous studies. RESEARCH QUESTION: To compare ankle and knee co-contraction (CCI), calculated using an EMG-driven method, between the groups and to examine their relationship with NCw. METHODS: Nine young (YG = 25.2 +/- 3.3 years old) and nine older (OG = 68.7 +/5.9 years old) adults walked on a treadmill at five speeds (YG: 1; 1.2; 1.4; 1.6; 1.8 m/s; OG: 0.6; 0.8; 1; 1.2; 1.4 m/s) while electromyography (sEMG) and oxygen consumption were measured. CCI were calculated around the ankle and knee for different parts of the gait cycle (entire gait cycle 0-100 %, stance phase 0-60 %, swing phase 60-100 %). RESULTS: NCw was significantly higher (25 %, averaged over the walking speeds) in OG as were Knee_CCI, Knee_CCI_swing and Knee_CCI_stance. Multiple regression models in YG, OG and YG + OG highlighted Ankle_CCI as the main contributor in NCw (β = 0.08-0.188, p < 0.05) with a positive relation between the two variables. SIGNIFICANCE: The present findings provide a better understanding of the association between muscle co-contraction and metabolic cost in older adults. It may help scientists and clinicians to further develop strategies aimed at neuromuscular rehabilitation as a means of improving mobility and independence among older adults.
BACKGROUND: The net metabolic cost of walking (NCw) and the co-activation of leg muscles are both higher in old adults (OG) than in young adults (YG). Nevertheless, the relation between the two remains unresolved, mainly due to the controversial co-activation measurement method used in previous studies. RESEARCH QUESTION: To compare ankle and knee co-contraction (CCI), calculated using an EMG-driven method, between the groups and to examine their relationship with NCw. METHODS: Nine young (YG = 25.2 +/- 3.3 years old) and nine older (OG = 68.7 +/5.9 years old) adults walked on a treadmill at five speeds (YG: 1; 1.2; 1.4; 1.6; 1.8 m/s; OG: 0.6; 0.8; 1; 1.2; 1.4 m/s) while electromyography (sEMG) and oxygen consumption were measured. CCI were calculated around the ankle and knee for different parts of the gait cycle (entire gait cycle 0-100 %, stance phase 0-60 %, swing phase 60-100 %). RESULTS: NCw was significantly higher (25 %, averaged over the walking speeds) in OG as were Knee_CCI, Knee_CCI_swing and Knee_CCI_stance. Multiple regression models in YG, OG and YG + OG highlighted Ankle_CCI as the main contributor in NCw (β = 0.08-0.188, p < 0.05) with a positive relation between the two variables. SIGNIFICANCE: The present findings provide a better understanding of the association between muscle co-contraction and metabolic cost in older adults. It may help scientists and clinicians to further develop strategies aimed at neuromuscular rehabilitation as a means of improving mobility and independence among older adults.