Hui-Lien Chien

Effects of severity of degeneration on gait patterns in patients with medial knee osteoarthritis

This study tested the hypothesis that patients with mild and severe medial knee osteoarthritis (OA) adopt different compensatory gait patterns to unload the deseased knee, in not only the frontal plane but also the sagittal plane. Fifteen patients with mild and 15 with severe bilateral medial knee OA, and 15 normal controls walked while the kinematic and kinetic data were measured. Compared to the normal group, both OA groups had significantly greater pelvic anterior tilt, swing-pelvis list, smaller standing knee abduction, as well as smaller standing hip flexor and knee extensor moments during stance. The severe group also had greater hip abduction, knee extension and ankle plantarflexion. The mild group successfully reduced the extensor moment and maintained normal abductor moment at the diseased knee mainly through listing and anterior tilting the pelvis. With extra compensatory changes at other joints and increased hip abductor moment, the severe group successfully reduced the knee extensor moment but failed to reduce the abductor moment. These results suggest that, apart from training of the knee muscles, training of the hip muscles and pelvic control are essential in the rehabilitative intervention of patients with knee OA, especially for more severe patients.

Control of the motion of the body's center of mass in relation to the center of pressure during high-heeled gait.

High-heeled shoes are associated with instability and falling, leading to injuries such as fracture and ankle sprain. Knowledge of the motion of the bodys center of mass (COM) with respect to the center of pressure (COP) during high-heeled gait may offer insights into the balance control strategies and provide a basis for approaches that minimize the risk of falling and associated adverse effects. The study aimed to investigate the influence of the base and height of the heels on the COM motion in terms of COM-COP inclination angles (IA) and the rate of change of IA (RCIA). Fifteen females who regularly wear high heels walked barefoot and with narrow-heeled shoes with three heel heights (3.9cm, 6.3cm and 7.3cm) while kinematic and ground reaction force data were measured and used to calculate the COM and COP, as well as the temporal-distance parameters. The reduced base of the heels was found to be the primary factor for the reduced normalized walking speed and the reduced frontal IA throughout the gait cycle. This was achieved mainly through the control of the RCIA during double-leg stance (DLS). The heel heights affected mainly the peak RCIA during DLS, which were not big enough to affect the IA. These results suggest young adults adopt a conservative strategy for balance control during narrow-heeled gait. The results will serve as baseline data for future evaluation of patients and/or older adults during narrow-heeled gait with the aim of reducing the risk of falling.

Effects of long-term wearing of high-heeled shoes on the control of the body's center of mass motion in relation to the center of pressure during walking

High-heeled shoes are associated with instability and falling, leading to injuries such as fracture and ankle sprain. This study investigated the effects of habitual wearing of high-heeled shoes on the bodys center of mass (COM) motion relative to the center of pressure (COP) during gait. Fifteen female experienced wearers and 15 matched controls walked with high-heeled shoes (7.3cm) while kinematic and ground reaction force data were measured and used to calculate temporal-distance parameters, joint moments, COM-COP inclination angles (IA) and the rate of IA changes (RCIA). Compared with inexperienced wearers, experienced subjects showed significantly reduced frontal IA with increased ankle pronator moments during single-limb support (p<0.05). During double-limb support (DLS), they showed significantly increased magnitudes of the frontal RCIA at toe-off and contralateral heel-strike, and reduced DLS time (p<0.05) but unaltered mean RCIA over DLS. In the sagittal plane experienced wearers showed significantly increased mean RCIA (p<0.05) and significant differences in the RCIA at toe-off and contralateral heel-strike (p<0.05). Significantly increased hip flexor moments and knee extensor moments at toe-off (p<0.05) were needed for forward motion of the trailing limb. The current results identified the change in the balance control in females after long-term use of high-heeled shoes, providing a basis for future design of strategies to minimize the risk of falling during high-heeled gait.

THE EFFECTS OF PEDAL RATES ON PEDAL REACTION FORCES DURING ELLIPTICAL EXERCISE

Despite the growing popularity in recent years of elliptical exercise (EE), little is known regarding the loadings applied to the body during EE. Since overloading to the body may lead to early fatigue of the muscles and increase the incidence of overuse injuries, such information is necessary for safe use of the elliptical trainer (ET) as a fitness tool. The current study aimed to determine the typical patterns and loading rates of the measured pedal reaction forces (PRF), and to quantify their differences from those during level walking, and the effects of pedaling rate. Fifteen male adults performed level walking and EE while 3D marker data, right PRFs and ground reaction forces (GRF) were measured. The parameters of the ET were set for two different pedal rates: 50 rpm and 70 rpm. For each pedal rate, the parameters were set to match the variables measured during level walking, with a mean step length of 55% leg length and no workload. During early stance the vertical PRF was smaller than the GRF, while the medial and posterior PRF were greater. PRFs also occurred during swing. Loading rates around heelstrike during EE were all smaller than those during walking. The medial, anterior and posterior PRF, as well as the medial and vertial loading rates increased with increasing pedal rates. The basic force patterns of EE and the effects of pedal rate were established in order to determine the true potential for such instrumentation in locomotion analysis. The results will be helpful for future related studies.

Inter-joint sharing of total support moments in the lower extremities during gait in narrow-heeled shoes of different heights

The study aimed to investigate the influence of the base and height of shoe heels on the total support moment (Ms) and individual joint contributions during gait. Fifteen healthy females walked barefoot and with narrow-heeled shoes (heel heights: 3.9, 6.3 and 7.3 cm) while kinematic and kinetic data were measured. Compared with the barefoot condition, the subjects maintained unaltered Ms in the sagittal plane in shod conditions. This was achieved by increasing the knee extensor moment to compensate for the diminished ankle plantarflexor moments in medium and high heel conditions. In the frontal plane, subjects in shod conditions had to sustain an increased Ms for balance control during late single-leg stance with increased knee abductor and ankle pronator moments as a result of the reduced base of the heels. The results will be helpful for future shoe designs to reduce fall risks and prevent relevant musculoskeletal problems Practitioner Summary: Knowledge of the influence of narrow-heeled shoes on lower limb support moments helps in shoe design to address fall risks. Gait analysis showed that females in narrow-heeled shoes maintained unaltered sagittal total support moments but sustained an increased demand in the frontal plane during late single-leg stance.

Gait changes in individuals with bilateral hallux valgus reduce first metatarsophalangeal loading but increase knee abductor moments.

Hallux valgus (HV), one of the most common foot pathologies in modern society, affects not only the foot itself, but also the other lower limb joints. The purpose of the study was to investigate the kinematic and kinetic changes in the lower limb joints in patients with bilateral HV during level walking. Twelve female patients with bilateral HV and 12 healthy female controls walked while three-dimensional kinematic and kinetic data were measured. Patients with HV were found to shift their center of pressure (COP) laterally away from the 1st metatarsophalangeal joint (MPJ), which helped unload the joint during late stance. The lateral shift of the COP in these patients was associated with the reduced toe-out angles of the foot as a result of increased internal rotation of the hip. However, this strategy increased the abductor moments at the knee, an index closely correlated with the medial load at the knee and a predictor of the onset and progression of medial OA. Early treatment of HV may be helpful not only for reducing foot pain and deformity, but also for preventing the potentially harmful loading at the knee, especially in those at risk of medial knee OA.

Enhancing the examiner's resisting force improves the validity of manual muscle strength measurements: application to knee extensors and flexors.

Abstract Lu, TW, Chien, HL, Chang, LY, and Hsu, HC. Enhancing the examiners resisting force improves the validity of manual muscle strength measurements: Application to knee extensors and flexors. J Strength Cond Res 26(9): 2364–2371, 2012—The purposes of this study were to test whether an examiners strength may affect the validity of the knee muscle strength measurements using a hand-held dynamometer (HHD) and whether enhancing the forces applied by an examiner using a resistance-enhanced dynamometer (RED) would improve measurement validity. Twenty-five young male volunteers (mean [±SD] age: 22.5 ± 1.7 years) without a history of injury to the test limb and 6 male and 6 female experienced examiners participated in this study. Maximum resisting forces of the knee flexors and extensors were measured using RED, HHD, and a dynamometer (Kin-Com). For all testing conditions, poor to moderate associations were found between the HHD and Kin-Com, whereas there was a good to excellent relationship between RED and Kin-Com. The systematic variations between RED and Kin-Com were also smaller than those between HHD and Kin-Com. The force values measured by RED were very close to those measured by Kin-Com. An examiners strength affects the validity of the measurements using HHD. Enhancing the forces applied by the examiner to the tested segment using RED appeared to improve the validity of muscle strength measurements.

KINEMATIC AND KINETIC ADAPTATIONS IN THE LOWER EXTREMITIES OF EXPERIENCED WEARERS DURING HIGH-HEELED GAIT

High-heeled shoes are associated with falling, leading to injuries such as fracture and ankle sprain. The study aimed to investigate the kinematic and kinetic adaptations in the lower extremities resulting from habitual use of high-heeled shoes. A total of 15 female experienced wearers and 15 matched controls walked with high-heeled shoes (7.3 cm) while kinematic and ground reaction force data were measured and used to calculate the joint angles and moments, as well as the temporal-distance parameters. Compared with inexperienced wearers, experienced wearers appeared to adopt a specific control strategy to improve the stability of the support ankle and knee while preventing excessive loading at the knee and hip. Increased hip abduction during early stance phase and increased pelvis rotation toward the ipsilateral side at contralateral heel-strike appeared to contribute toward the reduced step width for a better adjustment of the medio-lateral motion of the bodys center of mass in order to maintain stability. At the hip, increased abductor moments may help to increase the pelvis stability and prevent excessive loading at the knee, and reduced internal rotator moments may reduce the torsional loading at the hip. At the knee, reduced ranges of flexion-extension and adduction-abduction motions may increase its stability. At the ankle, increased external rotation angles, together with increased pronator and external rotator moments through increased ground reaction force, may enhance the ankle stability. The current results identified the changes in the kinematics and kinetics of the lower extremities in females after long-term use of high-heeled shoes, providing a basis for future development of training programs and design of new high-heeled shoes to help those who have higher risks of falling and injuries during high-heeled gait.

Effects of shoe heel height on the end-point and joint kinematics of the locomotor system when crossing obstacles of different heights

Abstract High-heeled shoes increase the risk of falling during walking, especially in the presence of obstacles. The study aimed to compare the end-point (foot/shoe) trajectories and joint angles of the lower extremities in 12 healthy females crossing obstacles of different heights while barefoot and when wearing narrow-heeled shoes (heel heights: 3.9, 6.3 and 7.3 cm). During obstacle-crossing, young females in narrow-heeled shoes maintained the same leading toe-clearance as when barefoot, irrespective of the heel height, primarily through increased plantarflexion of the leading swing ankle. However, the shoe heel-clearance was significantly reduced when compared with barefoot, presumably related to the difficulty in precisely sensing the position of the shoe-heel tip. With an increasing obstacle height, the toe-clearance, heel-clearance and shoe heel-clearance were reduced linearly, indicating an increasing risk of tripping over the obstacle. The results will be helpful for the design and development of strategies to reduce the risk of falling when wearing narrow-heeled shoes. Practitioner Summary: Knowledge of the influence of narrow-heeled shoes and obstacles on lower limb joint and end-point kinematics helps in shoe design to address fall risks. Compared to barefoot, narrow-heeled shoes reduced shoe heel-clearances, which were further reduced linearly with increasing obstacle height, indicating an increasing risk of tripping over the obstacle.

MUSCLE RECRUITMENT PATTERNS AND CONSISTENCY, AND THEIR CORRELATION WITH MOTOR TIME DURING A KARATE FRONT KICK

Adequate muscle recruitment patterns and their consistency are essential to achieve effective posture and force exertion during a karate front kick. The purpose of this study was to evaluate the reaction time (RT), motor time (MT) and total response time (TRT), as well as their correlation during a front kick, and to investigate the muscle recruitment patterns and their consistency during motor time. Fourteen professional karate athletes (age: 23.7 ± 2.6 years; height: 174.6 ± 7.1 cm; mass: 72.8 ± 10.7 kg) participated in the current study. Each subject was instructed to pose in combat stance first and then to use their right leg to kick at an instrumented kicking target as soon as they saw the start signal. Surface electromyograms (EMG) were recorded from 16 muscles. Start and stop signals from the instrumented target were also recorded synchronously to obtain the TRT. Significant correlation between MT and TRT indicated that MT was a primary determinant for the TRT of the kick. The muscle recruitment synergies during karate front kicks were identified. When performing a front kick, the athletes initiated the postural adjustments of the supporting leg prior to the onset of the voluntary kick. A successful motion of the karate front kick was dependent not only on the kicking leg, but also on the supporting leg. Tibialis anterior, biceps femoris and gluteus maximus of the supporting leg were the primary muscles providing stabilization, while the ankle and knee flexors, and tensor fasciae latae of the kicking leg were dominant muscles for the kicking movement. These results provide important information on the patterns and the consistencies of the muscle recruitment for coaching a karate front kick, which should be helpful for a better understanding of the motor control strategies of a karate front kick and for developing a suitable training protocol.