caa a22 4500 467941041 CHVBK 20180406153012.0 cr unu---uuuuu 170328e20060301xx s 000 0 eng 10.1007/s00421-005-0091-7 doi (NATIONALLICENCE)springer-10.1007/s00421-005-0091-7 Gajdosik Richard Clinical Kinesiology Laboratory, The School of Physical Therapy and Rehabilitation Science, The University of Montana, 59812-4680, Missoula, MT, USA aut Influence of a low-level contractile response from the soleus, gastrocnemius and tibialis anterior muscles on viscoelastic stress-relaxation of aged human calf muscle-tendon units [Elektronische Daten] [Richard Gajdosik] Measuring viscoelastic stress-relaxation (VSR) as the decline in passive tension over time when the skeletal muscle-tendon unit (MTU) is held in a lengthened position may be difficult in older people who may have difficulty relaxing. This study examined the VSR of the aged calf MTUs with a low-level involuntary contractile response from the soleus (S), gastrocnemius (G) and tibialis anterior (TA) muscles. Calf MTUs of 29 men and women (65-90years) were stretched to maximal dorsiflexion and held for 60s while torque (Nm) and surface electromyograms (SEMG) were recorded. Subjects with normalized SEMG (% of maximal voluntary contraction SEMG) of the S, G or TA <1% were assigned to Group 1 (n=14) and subjects with SEMG of the S or G ≥1% and <10%, or in the TA ≥1% were assigned to Group 2 (n=15). Although the mean total percent torque decline for Group 1 (17.9%) and Group 2 (16.6%) did not differ statistically, multiple regression analysis within Group 2 indicated that the G and TA SEMG accounted for 58% of its variation (R 2=0.581). The G SEMG from 0-15s accounted for 56% (r 2=0.563) of the variation in the percent decline normalized to total percent decline (100%). From 15-30s Group 2 had less percent decline (2%) than Group 1 (14%) (P=0.043) and the S and G SEMG accounted for 67% of its variation (R 2=0.673). The results indicated that a low-level involuntary contractile response from the S, G and TA muscles may be related to the VSR process of aged calf MTUs. Measuring VSR within time intervals normalized to the total percent decline offers a new method to study VSR, which should be measured with SEMG in the muscles <1% MVC SEMG to ensure valid measurements. Springer-Verlag, 2005 Aged calf muscle-tendon unit nationallicence Electromyography nationallicence Viscoelastic stress relaxation nationallicence European Journal of Applied Physiology Springer-Verlag 96/4(2006-03-01), 379-388 1439-6319 96:4<379 2006 96 421 https://doi.org/10.1007/s00421-005-0091-7 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00421-005-0091-7 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Gajdosik Richard Clinical Kinesiology Laboratory, The School of Physical Therapy and Rehabilitation Science, The University of Montana, 59812-4680, Missoula, MT, USA aut NATIONALLICENCE 773 0- European Journal of Applied Physiology Springer-Verlag 96/4(2006-03-01), 379-388 1439-6319 96:4<379 2006 96 421 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer