M Koyanagi

Asymmetric load-carrying in young and elderly women: Relationship with lower limb coordination

This study investigates balance during asymmetric load-carrying and how asymmetric loading affects lower limb coordination during gait. Walking with and without a hand-held bag was analyzed in five young and six elderly women using a 6-camera VICON system and two force plates. Balance and lower limb coordination were compared when walking with and without a bag and also between age groups. While carrying a bag, the trunk, head, and upper arm were recruited in both young and elderly women. With the load, the contralateral hip abduction torque increased, whereas the ipsilateral hip torque decreased. Intralimb and interlimb coordinations did not vary with the different load conditions. The only difference observed between the groups was the contralateral shoulder abduction. The elderly group abducted their shoulders to a greater extent, even when walking without a bag.

MOTION ANALYSIS OF A SINGLE-LIMB SQUAT WITH ISOKINETIC RESISTANCE

Background Resistive lateral leg reach exercise (RLLR), a single-limb squat with resistance, increases load on the gluteal muscles and is effective for preventing knee valgus moment, a major factor in anterior cruciate ligament (ACL) injury. To enhance the load during RLLR, we devised a novel isokinetic exercise machine. Objective To investigate the biomechanical and electromyographic (EMG) characteristics of the support leg during RLLR with isokinetic resistance (RLLR-I). Design Quasi-experimental. Setting Controlled laboratory setting. Participants 8 asymptomatic recreational-level female college athletes. Intervention Participants performed RLLR-I and lateral leg reach without resistance (LLR). The resistance device was set to 25 cm/s during RLLR-I. A three-dimensional motion capture system and force plate were used for motion analysis. Surface electrodes recorded the EMG at each muscle site: gluteus maximus (GMa), gluteus medius (GMe), rectus femoris, vastus medialis (VM), biceps femoris, adductor longus, soleus, and gastrocnemius. Main outcome measurements The external knee valgus/varus moment and the internal joint moment of the support leg were calculated using software. EMG root mean squared amplitude was normalized as a percentage of maximum voluntary contraction (%MVC). Results RLLR-I was characterized by a significantly larger internal hip abduction moment (2.2±1.0 Nm/kg) and significantly larger VM (152±54 %MVC), GMa (92±47 %MVC), and GMe (97±33 %MVC) activity compared with LLR (hip abduction moment: 1.5±0.7 Nm/kg; VM: 102±40 %MVC; GMa: 35±25 %MVC; and GMe: 38±13 %MVC). No significant external knee valgus moment occurred during RLLR-I. Conclusion RLLR-I serves to increase the load on the VM and gluteal muscles and is effective for preventing external knee valgus moment. These findings suggest that this novel isokinetic exercise will be useful for preventing ACL injury and in rehabilitation after ACL reconstruction.

Motion analysis of a single-limb squat with resistance

Background The activity of the gluteal muscles is important in preventing external valgus moment of the knee, which is a major factor in anterior cruciate ligament injury. Therefore, for the prevention of external valgus moment of the knee, we devised the resistive lateral leg reach exercise (RLLR), a single-limb squat with resistance which increases the load placed on the gluteal muscles. Objective This study investigated the biomechanical and electromyographic characteristics of the support leg during RLLR by comparison to those during the lateral leg reach exercise (LLR), which is similar to RLLR but with no resistance applied. Design Quasi-experimental study. Setting Controlled research laboratory. Participants 10 asymptomatic male college students. Interventions A 3D motion capture system and force plate were used to perform motion analysis. Surface electrodes recorded Electromyography activity at each muscle site (gluteus maximus, gluteus medius, rectus femoris, vastus medialis, biceps femoris, adductor magnus) during the exercises. Main outcome measurements External knee valgus/varus moment and internal hip abduction/adduction moment of the support leg were calculated using a software suite. EMG root mean squared amplitude was normalised to a percentage of maximum voluntary contraction (%MVC). Results RLLR was characterised by a significantly larger internal hip abduction moment (43.7±16.0 Nm) and larger gluteus maximus activity (141±109%MVC) than those observed during LLR (26.1±12.7 Nm, 81±52%MVC, respectively).External knee valgus moment almost did not occur through the motion in RLLR, but did occur during LLR (12.6±9.0 Nm). Conclusion RLLR serves to increase the load on the gluteal muscles and can be effective for the prevention of external knee valgus moment. It appears to be a promising exercise to prevent anterior cruciate ligament (ACL) injury and to use in rehabilitation training after ACL reconstruction.

BIOMECHANICAL ANALYSIS OF SINGLE-LEG SQUAT WITH ISOKINETIC AND CONSTANT RESISTIVE FORCE USING CONTROLLABLE EXERCISE EQUIPMENT

Background We have reported that a resistive single-leg squat (RSLS) exercise using exercise equipment that generates various resistance forces was effective for increasing the load on the gluteus medius and preventing knee valgus moment. However, the biomechanical characteristics of RSLS with each resistance forces have not been compared. Objective To compare difference of the biomechanical characteristics of RSLS between isokinetic resistance force (IF) and constant resistance force (CF). Design Quasi-experimental. Setting Controlled laboratory setting. Participants Six asymptomatic female college students. Interventions Participants performed RSLS with IF and CF. A motion capture system and force plate were used for motion analysis. Surface electrodes recorded the EMG activity of the muscles of the support leg. Main Outcome Measurements Joint moment of the support leg were calculated from 20° to 60° of knee flexion at 10° intervals. EMG data were normalized as a percentage of maximum voluntary contraction. Results In both the tasks, external knee valgus moment was prevented. Peak internal hip abduction moment was larger in IF (2.3±0.4 Nm/kg) than in CF (1.91±0.3 Nm/kg). Internal hip abduction moment was significantly larger in CF (1.4±0.2 Nm/kg) than in IF (1.1±0.3 Nm/kg) at 20° knee flexion, but larger in IF than in CF at 50° and 60° knee flexion. No significant difference in internal hip abduction moment was found at 30° and 40° knee flexion. EMG activities were significantly larger in IF (rectus femoris, 56±16%; vastus medialis, 85±38%; gluteus medius, 85±17%) than in CF (rectus femoris, 34±10%; vastus medialis, 48±23%; gluteus medius, 59±12%). Conclusion: IF was more useful for augmenting the activity of major muscles in the support leg and internal hip abduction moment at large knee flexion angles, whereas CF was more useful for augmenting internal hip abduction moment at small knee flexion angles, where ACL injury frequently occurs.

THE EFFECTS OF FUNCTIONAL GARMENT ON THE JUMP LANDING TASK

Background The effectiveness of wearing a brace to prevent sports injuries of the knee remains controversial. We examined the impact of functional newly developed garments. Objective To investigate the biomechanics of the knee joint when wearing the functional garment with lines in the fabric of different elasticities. Design Quasi-experimental. Setting Controlled laboratory setting. Participants 22 healthy male and female college students who participated in recreational sports. Interventions A single-leg drop jump onto the force plate was performed from a height of 30 cm. Infrared-reflective markers were attached to a total of 39 points for each subject. Body movements were tracked using a high-speed (200 Hz) three-dimensional motion analyzer and a force plate (ground reaction force of 1000 Hz). Long garments were used: two types of garments with fabric lines of hard and soft elasticity and the same garment with no processing (NT) as a control. Main outcome measurements External knee and knee valgus-varus moments as well as joint angle of the support leg were calculated using computer software. Results At 40 ms after ground contact, a significant decrease in the knee valgus angle was observed when wearing the Hard garment (5.33±3.32°) compared to the NT garment (1.33±4.91°; P<.05). A significantly low knee valgus-varus moment was observed when wearing the Hard garment (–6.08±7.07 Nm/kg) compared with the NT garment (0.93±8.60 Nm/kg) (P<.05). Conclusion The developed functional garment is considered to have reduced the knee abduction moment by controlling the knee valgus moment in a single-leg drop jump.The garment has the potential to avoid malalignment of the lower extremity and prevent sports injury of the knee joint.

EVALUATION OF A NEW QUADRICEPS STRENGTHENING EXERCISE FOR THE PREVENTION OF SECONDARY CARTILAGE INJURY IN PATIENTS WITH PCL INSUFFICIENCY: COMPARISON OF TIBIAL MOVEMENT IN PRONE AND SITTING POSITIONS DURING THE EXERCISE

Background Quadriceps strengthening exercise is recommended for patients with PCL insufficiency (PCLI), but posterior sag may occur under the influence of gravity in general leg extension in the sitting position (LES). We hypothesized that leg extension in the prone position (LEP) would be a safe strengthening exercise because the tibia is repositioned in patients with PCLI. Objective To compare tibial displacement (step off: SO) between LEP and LES, in order to verify the safety of LEP. Design Quasi-experimental study. Setting Controlled laboratory research. Patients 6 patients with PCL insufficiency (SO 2.9±1.6 mm). Interventions: LEP and LES were performed for isometricstrengthening with a flexion angle of the knee of 60 degrees and consistent force of knee extension. SO was measured on lateral X-P images of the knee. Differences in tibial movement between LEP and LES were evaluated using a paired t-test (P<0.05). Main outcome measurement SO measured by digitized XP. Results At the start position of LES, the tibia of all subjects was displaced posteriorly, and the tibia moved anteriorly 7.1±3.1 mm upon contraction of the quadriceps. In contrast, at the start position of LEP, the tibia was not displaced posteriorly in any subjects (SO=− 2.9±2.7 mm). Furthermore, there was significantly less anterior movement of the tibia during LEP (2.8±3.5 mm) than during LES (P<.05). Conclusions Since LES produced excessive anterior movement of the tibia upon contraction of the quadriceps, secondary cartilage injury may occur because of increased compression and shear force. In contrast, the repositioning of the tibia in LEP by gravity indicates it could be a safe quadriceps strengthening exercise for PCL insufficiency.

Posterior shear force and posterior tibial displacement using a sling bridge in patients with posterior cruciate ligament insufficiency

Background Rehabilitation training of hamstring muscle with deep knee flexion should be restricted following the posterior cruciate ligament (PCL) reconstruction because it stresses the PCL graft. To perform rehabilitation training of the hamstring muscle without the stress to the PCL, we have developed a sling bridge exercise (SB), which is a hamstring exercise with a sling at a lower leg to lift the buttocks in a supine position. Our hypothesis is that anterior traction force generated by a sling decrease strain on the PCL during SB. Objective To analyze posterior shear force and amount of posterior tibial displacement by the SB and compare with those by the conventional bridge (CB) exercise. Design Quasi-experimental study. Setting Controlled laboratory research. Participants Five healthy male volunteers and one patient with PCL insufficiency. Intervention Position of physical segments and force on floor were analyzed by a 3D motion capture system and force plate. Posterior tibial displacement was measured by lateral XP view of the knee during the exercises. Main outcome measurements Posterior shear force of the knee was calculated by using a biomechanical musculoskeletal model. Posterior tibial displacement was measured by digitised XP. Results Posterior shear force of the healthy volunteers was 849.0 ± 322.5 N during CB and 360.6 ± 75.5 N during SB. In a patient with the PCL insufficiency, side-to side difference in posterior tibial displacement by SB (1.2 mm) was smaller than that of CB (3.3 mm). Conclusion The SB hamstring exercise causes less posterior shear force and resulted in less posterior tibial displacement than a CB exercise. Therefore, a sling hamstring exercise is safer than a CB exercise in rehabilitation training for the patients with PCL reconstruction of the knee.

Safe and effective quadriceps femoris muscle exercise of resisted front bridge with a leg support in patients with anterior cruciate ligament insufficiency

Background Muscle strengthen exercise of quadriceps femoris is important but risky to the anterior cruciate ligament (ACL) graft, because quadriceps muscle exercise near the knee extension may causes anterior tibial translation. We developed a new exercise method, ‘resisted front bridge exercise with a leg support at proximal tibia’ (RFBP) in a prone position to avoid a risk. Our hypothesis is that RFBP is safe for the ACL graft and effective for muscle strengthen exercise. Objective To test our hypothesis, we investigated the anterior tibial translation and muscle contraction of quadriceps femoris during RFBP and compared with a front bridge exercise with a leg support at distal tibia (FBD). Design Quasi-experimental study. Setting Controlled laboratory research. Patients Three patients with ACL insufficiency participated in this study approved by the institutional ethical committee. Interventions Patients lied in a prone position with a leg support at proximal tibia. Leg extension exercise was ordered with a 20% of body-weight load on the back thigh to perform ‘RFBP’. Main outcome measurements Anterior tibial translation at 15° knee flexion was measured by fluoroscopy according to Franklins method. Electromyography (EMG) of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) were recorded and normalised against the values of maximum voluntary contraction (%MVC) of the involved leg. Results Anterior tibial translation of the involved knee in RFBP was not statistically significantly different from that of the uninvolved knee, and was smaller than that of the uninvolved knee in FBD in all patients by 4.4 mm in average. The%MVC of VM, VL, and RF muscle activities in the involved knee were 101.8%, 68.2%, and 75.6% during RFBP, respectively. Conclusion The resisted front bridge exercise with a leg support at proximal tibia is safe and effective for the quadriceps femoris at 15° knee flexion following ACL reconstruction surgery.

Evaluation of Anterior Tibial Translation and Muscle Activity during “Front Bridge” Quadriceps Muscle Exercise

In a postoperative rehabilitation program following anterior cruciate ligament (ACL) reconstruction surgery, it is most important to avoid exerting excessive stress on the reconstructed graft. We have been using a quadriceps muscle exercise, “front bridge” which is carried out in the prone position.