TY - JOUR

T1 - The role of agonist and antagonist muscles in explaining isometric knee extension torque variation with hip joint angle

AU - Bampouras, Theodoros M.

AU - Reeves, Neil D.

AU - Baltzopoulos, Vasilios

AU - Maganaris, Constantinos N.

N1 - The final publication is available at Springer via http://dx.doi.org/10.1007/s00421-017-3693-y

PY - 2017/10

Y1 - 2017/10

N2 - PurposeThe biarticular rectus femoris (RF), operating on the ascending limb of the force–length curve, produces more force at longer lengths. However, experimental studies consistently report higher knee extension torque when supine (longer RF length) compared to seated (shorter RF length). Incomplete activation in the supine position has been proposed as the reason for this discrepancy, but differences in antagonistic co-activation could also be responsible due to altered hamstrings length. We examined the role of agonist and antagonist muscles in explaining the isometric knee extension torque variation with changes in hip joint angle.MethodMaximum voluntary isometric knee extension torque (joint MVC) was recorded in seated and supine positions from nine healthy males (30.2 ± 7.7 years). Antagonistic torque was estimated using EMG and added to the respective joint MVC (corrected MVC). Submaximal tetanic stimulation quadriceps torque was also recorded.ResultJoint MVC was not different between supine (245 ± 71.8 Nm) and seated (241 ± 69.8 Nm) positions and neither was corrected MVC (257 ± 77.7 and 267 ± 87.0 Nm, respectively). Antagonistic torque was higher when seated (26 ± 20.4 Nm) than when supine (12 ± 7.4 Nm). Tetanic torque was higher when supine (111 ± 31.9 Nm) than when seated (99 ± 27.5 Nm).ConclusionAntagonistic co-activation differences between hip positions do not account for the reduced MVC in the supine position. Rather, reduced voluntary knee extensor muscle activation in that position is the major reason for the lower MVC torque when RF is lengthened (hip extended). These findings can assist standardising muscle function assessment and improving musculoskeletal modelling applications.

AB - PurposeThe biarticular rectus femoris (RF), operating on the ascending limb of the force–length curve, produces more force at longer lengths. However, experimental studies consistently report higher knee extension torque when supine (longer RF length) compared to seated (shorter RF length). Incomplete activation in the supine position has been proposed as the reason for this discrepancy, but differences in antagonistic co-activation could also be responsible due to altered hamstrings length. We examined the role of agonist and antagonist muscles in explaining the isometric knee extension torque variation with changes in hip joint angle.MethodMaximum voluntary isometric knee extension torque (joint MVC) was recorded in seated and supine positions from nine healthy males (30.2 ± 7.7 years). Antagonistic torque was estimated using EMG and added to the respective joint MVC (corrected MVC). Submaximal tetanic stimulation quadriceps torque was also recorded.ResultJoint MVC was not different between supine (245 ± 71.8 Nm) and seated (241 ± 69.8 Nm) positions and neither was corrected MVC (257 ± 77.7 and 267 ± 87.0 Nm, respectively). Antagonistic torque was higher when seated (26 ± 20.4 Nm) than when supine (12 ± 7.4 Nm). Tetanic torque was higher when supine (111 ± 31.9 Nm) than when seated (99 ± 27.5 Nm).ConclusionAntagonistic co-activation differences between hip positions do not account for the reduced MVC in the supine position. Rather, reduced voluntary knee extensor muscle activation in that position is the major reason for the lower MVC torque when RF is lengthened (hip extended). These findings can assist standardising muscle function assessment and improving musculoskeletal modelling applications.

KW - Electrical muscle stimulation

KW - Muscle activation capacity

KW - Quadriceps function

KW - Seated torque

KW - Supine torque

U2 - 10.1007/s00421-017-3693-y

DO - 10.1007/s00421-017-3693-y

M3 - Journal article

VL - 117

SP - 2039

EP - 2045

JO - European Journal of Applied Physiology

JF - European Journal of Applied Physiology

SN - 1439-6319

IS - 10

ER -