INFLUENCE OF KNEE FLEXION DURING SQUAT WITH AND WITHOUT LOAD USING AN INTEGRATED KNEE-FLEXION ANALYSIS SYSTEM (original) (raw)

A study of factors influencing muscle activity about the knee joint

Journal of Orthopaedic Research, 1983

Several factors influencing the myoelectric activity of muscles surrounding the knee joint were studied using fine-wire monopolar electrodes. The muscles studied included the vastus lateralis, vastus intermedius, rectus femoris, vastus medialis, gracilis, sartorius, biceps femoris, semimembranosus, semitendinosus, tensor fasciae latae, medial head of the gastrocnemius, and lateral head of the gastrocnemius. Muscle activity was measured in response to unidirectional loads tending to flex and extend the knee, and to combined loads of flexion-adduction, flexion-abduction, extension-adduction, and extension-abduction. Results indicate that the individual muscle responses are dependent upon the direction, magnitude, and combination of external moments, as well as on the flexion angle of the knee joint. Muscle response appeared to be influenced by certain intrinsic mechanical characteristics of the knee joint that tend to change the moment arms of the muscles as the knee moves. For example, the substantial changes in quadriceps myoelectric activity with knee flexion, with constant load applied, can be related to the movement of the tibial-femoral contact changing the lever arm of the quadriceps mechanism. This study indicates that the mechanics of the knee joint must be taken into consideration while attempting to interpret or predict the load response of muscles crossing the knee joint.

Effects of Hip Flexion on Knee Extension and Flexion Isokinetic Angle-Specific Torques and HQ-Ratios

Sports Medicine - Open, 2021

Background and Methods During isokinetic knee strength testing, the knee flexion angles that correspond to the measured torque values are rarely considered. Additionally, the hip flexion angle during seated testing diverges from that in the majority of daily life and sporting activities. Limited information concerning the influence of hip angle, muscle contraction mode, and velocity on the isokinetic knee strength over the entire range of motion (ROM) is available. Twenty recreational athletes (10 females, 10 males; 23.3 ± 3.2 years; 72.1 ± 16.5 kg; 1.78 ± 0.07 m) were tested for isokinetic knee flexion and extension at 10° and 90° hip flexion with the following conditions: (i) concentric at 60°/s, (ii) concentric at 180°/s, and (iii) eccentric at 60°/s. The effects of hip angle, contraction mode, and velocity on angle-specific torques and HQ-ratios as well as conventional parameters (peak torques, angles at peak torque, and HQ-ratios) were analyzed using statistical parametric mapp...

Comparison of Common Methodologies for the Determination of Knee Flexor Muscle Strength

International Journal of Sports Physical Therapy, 2021

Background Knee flexion strength may hold important clinical implications for the determination of injury risk and readiness to return to sport following injury and orthopedic surgery. A wide array of testing methodologies and positioning options are available that require validation prior to clinical integration. The purpose of this study was to 1) investigate the validity and test-retest reliability of isometric knee flexion strength measured by a fixed handheld dynamometer (HHD) apparatus compared to a Biodex Dynamometer (BD), 2) determine the impact of body position (seated versus supine) and foot position (plantar- vs dorsiflexed) on knee flexion peak torque and 3) establish the validity and test-retest reliability of the NordBord Hamstring Dynamometer. Study Design Validity and reliability study, test-retest design. Methods Forty-four healthy participants (aged 27 ± 4.8 years) were assessed by two raters over two testing sessions separated by three to seven days. Maximal isome...

Dependency of knee extension torque on different types of stabilisation

International Journal of Human Factors Modelling and Simulation, 2012

Can isolated single-joint torque measurements be used for every practical use case concerning strength prediction or does the possibility of support and stabilisation influence the results? Some studies show that, for example, using or not using handgrips influences maximum knee extension joint torques. This suggests that a muscle can transmit a higher force than it can generate. This would have incisive consequences on digital human modelling. In this case, a strength prediction model would need the information about possible contact points that could increase the resulting joint torque by recruiting further muscle groups. In this study, three stabilisation methods (waist belt, upper body restraint, handgrips and waist belt) were used for maximum isometric knee joint torque measurements using 21 young, male subjects. The results show that in contrast to some earlier studies no significant differences could be obtained. Based on the results recommendations for appropriate stabilisation are given.

Observations on the knee functional axis during active movements

Estimating the knee functional axis (KFA) is crucial to both correctly implanting the prosthesis and accessing the joint kinematics. Researchers have mainly reported KFA by manual management of flexion–extension movements, which are passively performed without any voluntary movements. Active touch and movement refers to what is ordinarily called as touching, which is defined as variations in skin stimulation caused by variations in a person’s motor activity. The difference is very important for the individual. However, it has not been emphasized in the biomechanical literatures. This study aims to confirm the distinction between touching and being touched. We are particularly interested in measuring the instantaneous axes of the knee (IAK) during locomotion. This geometrical “pattern” of the IAK is altered along with the touch pattern by the mechanical necessities of terrestrial movement.

Knee joint kinetics in relation to commonly prescribed squat loads and depths

Cotter, JA, Chaudhari, AM, Jamison, ST, and Devor, ST. Knee joint kinetics in relation to commonly prescribed squat loads and depths. J Strength Cond Res 27 : 1765-1774, 2013-Controversy exists regarding the safety and performance benefits of performing the squat exercise to depths beyond 908 of knee flexion. Our aim was to compare the net peak external knee flexion moments (pEKFM) experienced over typical ranges of squat loads and depths. Sixteen recreationally trained men (n = 16; age, 22.7 6 1.1 years; body mass, 85.4 6 2.1 kg; height, 177.6 6 0.96 cm; mean 6 SEM) with no previous lower-limb surgeries or other orthopedic issues and at least 1 year of consistent resistance training experience while using the squat exercise performed single-repetition squat trials in a random order at squat depths of above parallel, parallel, and below parallel. Less than 1 week before testing, 1RM values were found for each squat depth. Subsequent testing required the subjects to perform squats at the 3 depths with 3 different loads: unloaded, 50% 1RM, and 85% 1RM (9 total trials). Force platform and kinematic data were collected to calculate pEKFM. To assess the differences among loads and depths, a 2-factor (load and depth) repeated measures analysis of variance with significance set at the p , 0.05 level was used. Squat 1RM significantly decreased 13.6% from the aboveparallel to the parallel squat and another 3.6% from the parallel to the below-parallel squat (p , 0.05). Net peak external knee flexion moments significantly increased as both squat depth and load were increased (p # 0.02). Slopes of pEKFM were greater from unloaded to 50% 1RM than when progressing from 50% to 85% 1RM (p , 0.001). The results suggest that typical decreases in squat loads used with increasing depths are not enough to offset increases in pEKFM.

Experimental measurement of flexion-extension movement in normal and osteoarthritic human knee

Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie, 2013

The paper presents a comparative experimental study of flexion-extension movement in normal and osteoarthritic human knee. Measurements were performed on a group of seven healthy subjects and on a group of five patients with OA knees, for which experimental data were acquired for walking cycles on treadmill. Using an electrogoniometer-based acquisition system, the data were collected during the experimental gait on a treadmill with the speed equal to 3.6 km/h. The flexion angle during the gait cycle revealed differences with respect to flexion magnitude between the OA patients and the healthy subjects group. Statistical analysis demonstrated that the knee flexion angles were significantly different for experimental measurements of the OA patients' knees and healthy knees, but, also, the healthy knees of the patients were on average less flexed than gait cycle of the healthy subjects.

Relative torque contribution of vastus medialis muscle at different knee angles

Acta Physiologica, 2008

Aim: We investigated the relative contribution of the vastus medialis (VM) muscle to total isometric knee extension torque at 10°, 30°, 60°and 90°knee flexion. In the past a more prominent role of the VM muscle at more extended knee angles has been put forward. However, different components of the quadriceps muscle converge via a common distal tendon. We therefore hypothesized that the relative contribution of the VM to total knee extension torque would be similar across angles. Methods: At each knee angle the EMG isometric torque relations [20%, 25%, 30%, 35% maximal voluntary contraction (MVC)] of the rectus femoris (RF), vastus lateralis (VL) and VM muscle were established in 10 healthy male subjects; rectified surface EMG was normalized to M-wave area. Subsequently, the VM was functionally eliminated by selective electrical surface stimulation with occluded blood flow. Results: There was no evidence for preferential activation of VM at any of the knee angles. Following VM elimination, total knee extension torque during maximal femoral nerve stimulation (three pulses at 300Hz) at 10°, 30°, 60°and 90°, respectively, decreased (P < 0.05) to (mean AE SD): 75.7 AE 12.2, 75.1 AE 9.3, 78.2 AE 7.2 and 76.0 AE 5.8% (P > 0.05 among knee angles). In addition, during voluntary contractions at 20% MVC the increases in torque output of RF and VL compensating for the loss of VM function were calculated from the increases in EMG and found to be similar (P > 0.05) at 10°, 30°, 60°and 90°values (%MVC), respectively, were: 9.1 AE 6.8, 7.5 AE 2.9, 5.9 AE 3.7 and 6.9 AE 3.4. Conclusion: The present findings support our hypothesis that the VM contributes similarly to total knee extension torque at different knee angles.