Effectiveness of knee pad as an additional device for wheelchairs in improving upper-limb dexterity during seated tasks: a pilot study.

[Purpose] This study aimed to examine how supporting the knee from the front with a knee pad affected upper-limb dexterity while sitting. [Participants and Methods] A total of 14 healthy adult males were included in the study. As a measure of upper-limb dexterity, the number of pins was counted when the Purdue pegboard test was performed for 60 seconds. In addition, the ease of task performance was assessed using the visual analogue scale. There were two experimental conditions, with and without knee pad. The paired t-test was used to detect differences between the two conditions. A p-value of 0.05 was considered statistically significant. [Results] The Purdue pegboard test was 29.4 ± 2.5 and 27.9 ± 3.6 pins with and without knee pad, respectively. The VAS was 76.1 ± 10.3 and 62.9 ± 14.1 with and without knee pad, respectively. Both measured values were significantly higher with knee pad than without. [Conclusion] Supporting the knees from the front with knee pad improves upper-limb functionality while sitting, making it easier to perform seated tasks.

Effect of shape of back support adjustment on shear force applied to buttocks when tilt-in-space and reclining functions are combined in wheelchairs.

PURPOSE: This study aimed to investigate the effect of the shape of the back support adjustment on the shear force applied to the buttocks when tilt-in-space and reclining functions are combined in wheelchairs. MATERIALS AND METHODS: Fourteen healthy adult men were included in the study. The force plate was used to measure the parallel force as shear force. The measurement posture, leaning against the back support of an experimental chair, was a comfortable sitting posture. The tilt-in-space angle was set to 15°. The back support was inclined at increasing angles, starting from the upright position (IUP), proceeding to a fully reclined position (FRP), and returning to the upright position (RUP). The experimental conditions were as follows: adjusting the back-support shape (aBS) and non-adjusting the back support shape (non-aBS). RESULTS: Positive values indicate a parallel force applied to the buttocks posteriorly. The average values in the aBS condition were 3.4 ± 2.3, 13.6 ± 2.2, and -7.1 ± 2.4% body weight in the IUP, FRP, and RUP, respectively. The average values in the non-aBS condition were 3.8 ± 2.5, 11.4 ± 2.1, and -6.2 ± 3.1% body weight in the IUP, FRP, and RUP, respectively. There were significant differences between the two conditions in FRP (p < 0.01). CONCLUSION: These findings suggest that the shape of the back support adjustment function increased the shear force applied to the buttocks posteriorly when the back support was inclined backwards using both the tilt-in-space and reclining functions.IMPLICATIONS FOR REHABILITATIONWhen utilizing both the tilt-in-space and reclining functions to incline the back support, the shear force applied to the buttocks is greatly affected by the shape of the back support.The shape of back support adjustment is a function that can stabilize elderly persons' sitting posture, but it may increase the external force applied to the buttocks and back.

An investigation into the effectiveness of a novel wheelchair seat-cover assembly for the reduction of forces exerted onto the buttocks.

PURPOSE: This purpose was to investigate developed seat-cover assemblies' effect on decreasing the fluctuation of the shear force exerted onto the buttocks as the factors causing decubitus ulcers when the back-support was inclined. MATERIALS AND METHODS: The participants were 10 wheelchair users. The force plate was used to measure the horizontal force as the shear force. The back-support was inclined at increasing angles, starting from the upright position (IUP), then proceeding to a fully reclined position (FRP), and returning to the upright position (RUP). The experimental conditions were two conditions; the seat-cover assembly conditions and without the seat-cover assembly as the control conditions. RESULTS: The average values in the seat-cover assembly condition were 14.4 ± 3.3, 13.9 ± 2.3, and 17.3 ± 3.3% body weight in the IUP, FRP, and RUP, respectively. The average values in the control condition were 14.8 ± 2.6, 11.4 ± 1.7, and 24.0 ± 6.7% body weight in the IUP, FRP, and RUP, respectively. In the FUP and the RUP, there were significant differences between two conditions (p < .01). CONCLUSION: These results suggested that the shear force exerted onto the buttocks may to be decreased by using novel seat-cover assembly.Implications for rehabilitationIt is possible to decrease the fluctuations in the shear force by moving the body up and down according the novel seat-cover assembly attached the back-support incline.Disabled, older individuals can be provided with a comfortable life on a reclining wheelchair while preventing decubitus ulcers.

Investigation of the effect of a 15-degree tilt-in-space on the fluctuation of shear forces exerted on the buttocks when the back support is reclined.

[Purpose] This study aimed to investigate the effect of the combination of 15° tilt-in-space and recline angles on the fluctuation of shear forces exerted on the buttocks. [Participants and Methods] The participants were 11 healthy adult males. The parameters of the shear forces were the parallel and perpendicular forces exerted on the buttocks as measured by a force plate. The two conditions tested were T0R100-130 and T15R100-130. The tilt-in-space angles were set to 0° and 15° in the T0R100-130 and T15R100-130 conditions, respectively. The reclining angles were determined to be 100° to 130° in both conditions. [Results] Upon comparing the two conditions, the parallel and the perpendicular forces exerted on the buttocks in the T15R100-130 condition were significantly lower than those in the T0R100-130 condition in all positions of back support. Upon comparing the fluctuation values of the parallel and perpendicular forces, those applied in the T15R100-130 condition were significantly higher than those in the T0R100-130 condition. [Conclusion] These results suggest that the fluctuation of shear forces exerted on the buttocks could be decreased by using a combination of 15° tilt-in-space and reclining functions.

Trunk muscle activation patterns during active hip abduction test during remission from recurrent low back pain: an observational study.

BACKGROUND: The active hip abduction test (AHAbd) is widely used to evaluate lumbopelvic stability, but the onset of trunk muscle activation during the test in individuals with recurrent low back pain (rLBP) has not been investigated so far. It is important to investigate the pattern of trunk muscle activation during the AHAbd test to provide insight into the interpretation of observation-based assessment results; this may help to create exercise therapy interventions, from a movement control perspective, for people seeking treatment for rLBP. The purpose of this study was to compare the timing of trunk muscle activation between individuals with and without rLBP and to assess potential differences. METHODS: Seventeen subjects in remission from rLBP and 17 subjects without rLBP were recruited. We performed surface electromyography of the transversus abdominis/internal abdominal oblique, external oblique, erector spinae, and gluteus medius muscles during the AHAbd test on both sides. The onset of trunk muscle activation was calculated relative to the prime mover gluteus medius. The independent-samples t- and Mann-Whitney U tests were used to compare the onset of trunk muscle activation between the two groups. RESULTS: The onset of transversus abdominis/internal abdominal oblique activation on the ipsilateral (right AHAbd: -3.0 ± 16.2 vs. 36.3 ± 20.0 msec, left AHAbd: -7.2 ± 18.6 vs. 29.6 ± 44.3 ms) and contralateral sides (right AHAbd: -11.5 ± 13.9 vs. 24.4 ± 32.3 ms, left AHAbd: -10.1 ± 12.5 vs. 23.3 ± 17.2 ms) and erector spinae on the contralateral side (right AHAbd: 76.1 ± 84.9 vs. 183.9 ± 114.6 ms, left AHAbd: 60.7 ± 70.5 vs. 133.9 ± 98.6 ms) occurred significantly later in individuals with rLBP than in individuals without rLBP (p < 0.01). During the left AHAbd test, the ipsilateral erector spinae was also activated significantly later in individuals with rLBP than in individuals without rLBP (71.1 ± 80.1 vs. 163.8 ± 120.1 ms, p < 0.05). No significant difference was observed in the onset of the external oblique activation on the right and left AHAbd tests (p > 0.05). CONCLUSIONS: Our results suggest that individuals with rLBP possess a trunk muscle activation pattern that is different from that of individuals without rLBP. These findings provide an insight into the underlying muscle activation patterns during the AHAbd test for people with rLBP and may support aggressive early intervention for neuromuscular control.

Immediate Effect of Restricted Knee Extension on Ground Reaction Force and Trunk Acceleration during Walking.

Gait parameters calculated from trunk acceleration reflect the features of gait; however, they cannot evaluate the gait pattern corresponding to the gait cycle. This study is aimed at investigating the differences in gait parameters calculated from trunk acceleration during gait corresponding to the gait cycle in healthy subjects with restricted knee extension. Participants included eight healthy volunteers who walked normally (NW) and with knee orthosis that restricted knee extension (ER). The ground reaction force (GRF), joint angles, and trunk acceleration during walking were measured using four force plates, a three-dimensional motion analysis system, and an inertial measurement unit. The peak GRF of the vertical components, joint ranges of motion, and moments of force were analyzed. The root mean square (RMS) and amplitude peak ratio (AR) of autocorrelation function were calculated from the trunk acceleration waveform. The first peak GRF and peak ankle dorsiflexion angles significantly increased during ER. The peak hip extension, knee flexion, knee extension angles, and the peak moment of knee extension significantly decreased during ER compared to that during NW. The acceleration AR significantly decreased during ER compared to that during NW. There was no significant difference in the RMS between the two conditions. The acceleration AR may show the temporal postural structure with restricted knee extension from the terminal stance phase for the ipsilateral limb to the initial stance phase for the contralateral limb. These results suggest that novel metrics for accelerometry gait analysis can reveal gait abnormalities, with restricted knee extension corresponding to the gait cycle.

Effect of asymmetrical buttock pressure on forces exerted in buttock movement when using a reclining chair.

[Purpose] To clarify the effect of asymmetrical buttock pressure on the shear forces exerted on a buttock. [Participants and Methods] Sixteen healthy adult males participated in this study. A cushion 0 or 2 cm high was placed on the left side of the seat for all participants. The 0- and 2-cm height conditions were called "without difference condition" and "difference condition", respectively. The back support was inclined at increasing angles, starting at the upright position, to a fully reclined position, and back to the upright position. [Results] With the "difference condition", the force on the left buttock was 147.4% body weight and that on the right buttock was 105.6% body weight. In contrast, with the "without difference condition", there was no significant difference in the force on the left buttock and right buttock in terms of percent body weight. [Conclusion] Our results suggest that asymmetrical buttock pressure while in the sitting position causes a difference in shear force exerted on the left and right buttocks when using a reclining chair.

Immediate changes in trunk muscle activation patterns during a lifting task following an abdominal drawing-in exercise in subjects with recurrent low back pain.

BACKGROUND: The abdominal drawing-in exercise could help improve delayed transversus abdominis (TrA) activation during limb movement in subjects with recurrent low back pain (rLBP). However, little is known about whether the same effect is observed during lifting tasks in subjects with rLBP. OBJECTIVE: This study aimed to clarify whether a single session of abdominal drawing-in exercise could correct the altered trunk muscle activation patterns during a lifting task in subjects with rLBP. METHODS: Fifteen subjects with rLBP performed lifting tasks before and immediately after three sets of 10 repetitions of isolated TrA voluntary contractions. The time of onset and activation amplitude during the lifting tasks were measured by surface electromyography (EMG) and compared between the trials before and immediately after exercise. RESULTS: During lifting, the onset of internal abdominal oblique/TrA (IO/TrA) and multifidus activation occurred earlier, the EMG amplitude of IO/TrA increased, and the EMG amplitude of erector spinae and multifidus decreased, compared with the pre-exercise data. CONCLUSIONS: These results suggest a possibility that the abdominal drawing-in exercise might be effective in improving the muscle recruitment pattern in people with rLBP.

Muscle activity during backward perturbation response in patients with clinical vertebral compression fractures.

The present study examined muscle activity in response to backward perturbation in patients with clinical vertebral compression fracture (CVCF). The subjects were 32 patients aged 65 years and above consisting of 16 each with (CVCF group) and without (control group) CVCF. The time to peak activity, and time of onset of muscle activity of the anterior tibial, vastus medialis, and rectus abdominis muscles when unexpected backward perturbation was applied were evaluated by surface electromyography. The strength of perturbation was 4% or 6% of the subject's body weight. In addition, the presence of the stepping reaction to perturbation, severity of low back pain, and vertebral alignment were evaluated. Each item was compared between the two groups. In the CVCF group, kyphosis and severity of low back pain were significantly more severe, the time to peak activity of the anterior tibial muscle after the application of perturbation at 6% of the body weight was significantly shorter, and the time of onset of activity of the rectus abdominis muscle was significantly delayed. This suggests that the time to peak activity of the anterior tibial muscle is shortened and the time of onset of activity of the rectus abdominis muscle is delayed in unexpected backward perturbation in patients with CVCF.

Tape measure-based real-time feedback during the abdominal draw-in maneuver facilitates isolated transverse abdominal contraction.

[Purpose] Although the abdominal draw-in maneuver improves delayed onset of transverse abdomen in patients with low back pain, it is difficult to perform. We investigated whether the maneuver with tape measure-based feedback was more effective in facilitating isolated transverse abdominal muscle contractions than that without feedback in healthy participants. [Participants and Methods] Twenty healthy males performed the maneuver without feedback (control condition) and then with feedback using a tape measure (tape measure condition) in the crook lying, sitting, and standing positions. A B-mode ultrasonography imaging system was used to determine lateral abdominal muscle thicknesses, the percent changes from before the maneuver were calculated for each condition, and the main effects and interactions for each tested muscle were determined. [Results] The percent change in the thickness of the transverse abdominal muscle was significantly greater under the tape measure condition than under the control condition. The percent change in internal oblique thickness during the maneuver was significantly greater in the standing position than in the crook lying or sitting positions. Significant condition-by-position interactions were not observed for any of the examined muscles. [Conclusion] The abdominal draw-in maneuver with tape measure-based feedback may be more effective at facilitating isolated transverse abdominal contractions in all the positions than that without feedback.

Altered trunk muscle recruitment patterns during lifting in individuals in remission from recurrent low back pain.

Changes in the recruitment pattern of trunk muscles may contribute to the development of recurrent or chronic symptoms in people with low back pain (LBP). However, the recruitment pattern of trunk muscles during lifting tasks associated with a high risk of LBP has not been clearly determined in recurrent LBP. The present study aimed to investigate potential differences in trunk muscles recruitment patterns between individuals with recurrent LBP and asymptomatic individuals during lifting. The subjects were 25 individuals with recurrent LBP and 20 asymptomatic individuals. Electromyography (EMG) was used to measure onset time, EMG amplitude, overall activity of abdominal muscles, and overall activity of back muscles during a lifting task. The onsets of the transversus abdominis/internal abdominal oblique and multifidus were delayed in the recurrent LBP group despite remission from symptoms. Additionally, the EMG amplitudes of the erector spinae, as well as the overall activity of abdominal muscles or back muscles, were greater in the recurrent LBP group. No differences in EMG amplitude of the external oblique, transversus abdominis/internal abdominal oblique, and multifidus were found between the groups. Our findings indicate the presence of an altered trunk muscle recruitment pattern in individuals with recurrent LBP during lifting.

Association between trunk acceleration during walking and clinically assessed balance in patients with stroke.

BACKGROUND: Accelerometers provide information regarding balance and gait, but they are rarely used in clinical settings for stroke patients. Clinically, balance is assessed with simple tests, but their relationships with accelerometry results after stroke are unknown. OBJECTIVE: We examined the relationship between accelerometry-assessed gait indices calculated from trunk acceleration and results of the Timed Up and Go (TUG) and Berg Balance Scale (BBS) tests in stroke patients. METHODS: Twenty-nine stroke patients completed assessments with the TUG, BBS, and trunk acceleration during walking using a tri-axial accelerometer. The root mean square (RMS), stride regularity (SR), and step symmetry (SS), which indicate gait fluctuations, regularity, and symmetry, respectively, were calculated based on trunk acceleration. These were calculated in the vertical (VT), anteroposterior, and mediolateral directions. A multiple linear regression analysis was performed to determine whether these gait indices contributed independently to TUG and BBS results. RESULTS: VT-RMS and VT-SS were significant determinants of TUG, and VT-SS, VT-RMS, and VT-SR were significant determinants of BBS. CONCLUSIONS: This study suggested that the gait indices calculated from trunk acceleration that were relevant to balance were those in the VT direction. These may be useful for evaluating dynamic gait balance in patients with stroke.

Intra-rater and inter-rater reliabilities of real-time acceleration gait analysis system.

PURPOSE: The purposes of this study were to construct a real-time acceleration gait analysis system equipped with software to analyse real-time trunk acceleration during walking and to examine the intra-rater and inter-rater reliabilities of the this system. METHODS: This system has been comprised of an accelerometer, an acceleration amplifier, a transmitter, two foot switches, a receiver and a personal computer installed with the real-time acceleration analysis software. The acceleration signals received were analysed using the real-time acceleration analysis software, and gait parameters were calculated. The subjects were 20 healthy individuals and two raters. The intra-rater and inter-rater reliabilities of the measurement results obtained from this system were examined by performing intraclass correlation coefficients (ICC) and Bland-Altman analysis. RESULTS: The intra-rater and inter-rater ICCs ranged from 0.61 to 0.92 in any gait parameters. In the Bland-Altman analysis, neither fixed nor proportional bias was found in any of the gait parameters. CONCLUSIONS: From the ICC and Bland-Altman analysis results, the gait measurement using this system clearly demonstrates that the intra-rater and inter-rater measurements had good reproducibility. Owing to this system, we can improve the clinical efficiency of gait analysis and gait training for physiotherapy. Implication for Rehabilitation This study focused on the advantage of a gait analysis method using an accelerometer and constructed a gait analysis system that calculates real-time gait parameters from trunk acceleration measurements during walking. The gait analysis using this system has good intra-rater and inter-rater reliabilities, and using this system can improve the clinical efficiency of gait analysis and gait training.

Investigation of effect of leg support elevation timing on the horizontal force acting on the buttocks in a reclining wheelchair.

[Purpose] The purpose of this study was to investigate the effect of the timing of leg support elevation on the horizontal force acting on the buttocks in a reclining wheelchair. [Subjects and Methods] The participants were 17 healthy men. Two experimental conditions were tested: the leg-down and leg-up conditions. The back support was reclined at increasing angles, from the initial upright position (IUP), proceeding to the fully reclined position (FRP), and returned to the upright position (RUP). The posterior inclination phase was from IUP to FRP, and the returning inclination phase was from FRP to RUP. [Results] The horizontal force under the leg-up condition was significantly higher than that under the leg-down condition in all positions of back support. [Conclusion] The leg supports should be positioned downward before reclining the back support of a wheelchair.

Individuals with chronic low back pain demonstrate delayed onset of the back muscle activity during prone hip extension.

Prone hip extension (PHE) is commonly used in the evaluation of the stability of the lumbopelvic region. There is little evidence of difference in muscle activity onset timing between healthy individuals and individuals with chronic low back pain (CLBP) during PHE. The purpose of this study was to determine if individuals with and without CLBP differ in the onset time of the trunk and hip extensor muscles activity during PHE. The participants were 20 patients with CLBP and 20 healthy individuals. Electromyography data of the erector spinae, multifidus, gluteus maximus, and semitendinosus were collected during PHE using a surface electromyograph. Relative differences in the onset times between each muscle and the prime mover (i.e., the semitendinosus) were calculated. The onsets of the bilateral multifidus and contralateral erector spinae were significantly delayed in the CLBP group compared with the healthy group (p<0.001), despite the onset timings of leg movement not being significantly different between the groups. The onset times of the gluteus maximus and ipsilateral erector spinae showed no significant differences between the groups. These results suggest that individuals with CLBP use an altered, and possibly inadequate, trunk muscle recruitment pattern.

Effect of abduction and external rotation of the hip joint on muscle onset time during prone hip extension with knee flexion.

[Purpose] This study investigated the effect of hip position on muscle onset time during prone hip extension with knee flexion. [Subjects] The study included 21 healthy male volunteers. [Methods] Muscle onset times of the right gluteus maximus, right hamstrings, bilateral lumbar erector spinae, and bilateral lumbar multifidus were measured using surface electromyography during right hip extension with knee flexion in the prone position. Measurements were made with the hip in 3 positions: (1) neutral, (2) abduction, and (3) abduction and external rotation. [Results] Gluteus maximus onset relative to the hamstrings was significantly earlier with hip abduction and with hip abduction and external rotation compared with that with the hip in the neutral position. Gluteus maximus onset relative to the hamstrings was significantly earlier with hip abduction and external rotation compared with that with hip abduction. The bilateral multifidus and left lumbar erector spinae onset times relative to the hamstrings were significantly earlier with hip abduction and external rotation compared with those with hip abduction and with the hip in the neutral position. [Conclusion] Abduction and external rotation of the hip during prone hip extension with knee flexion is effective for advancing the onset times of the gluteus maximus, bilateral multifidus, and contralateral lumbar erector spinae.

Excitability changes in intracortical neural circuits induced by differentially controlled walking patterns.

Our previous single-pulse transcranial magnetic stimulation (TMS) study revealed that excitability in the motor cortex can be altered by conscious control of walking relative to less conscious normal walking. However, substantial elements and underlying mechanisms for inducing walking-related cortical plasticity are still unknown. Hence, in this study we aimed to examine the characteristics of electromyographic (EMG) recordings obtained during different walking conditions, namely, symmetrical walking (SW), asymmetrical walking 1 (AW1), and asymmetrical walking 2 (AW2), with left to right stance duration ratios of 1:1, 1:2, and 2:1, respectively. Furthermore, we investigated the influence of three types of walking control on subsequent changes in the intracortical neural circuits. Prior to each type of 7-min walking task, EMG analyses of the left tibialis anterior (TA) and soleus (SOL) muscles during walking were performed following approximately 3 min of preparative walking. Paired-pulse TMS was used to measure short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the left TA and SOL at baseline, immediately after the 7-min walking task, and 30 min post-task. EMG activity in the TA was significantly increased during AW1 and AW2 compared to during SW, whereas a significant difference in EMG activity of the SOL was observed only between AW1 and AW2. As for intracortical excitability, there was a significant alteration in SICI in the TA between SW and AW1, but not between SW and AW2. For the same amount of walking exercise, we found that the different methods used to control walking patterns induced different excitability changes in SICI. Our research shows that activation patterns associated with controlled leg muscles can alter post-exercise excitability in intracortical circuits. Therefore, how leg muscles are activated in a clinical setting could influence the outcome of walking in patients with stroke.

Influence of rotational axis height of back support on horizontal force applied to buttocks in a reclining wheelchair.

BACKGROUND: Studies have not been conducted to investigate the influence of the height of the rotational axis of a wheelchair's back support on the shear force applied to the buttocks during the reclining motion. OBJECTIVES: The purpose of this study was to investigate the influence of the difference in the rotational axis position of back support in the vertical direction on the horizontal force applied to buttocks for preventing decubitus ulcers. STUDY DESIGN: Repeated measures design. METHODS: The subjects were 13 healthy adult men without leg and/or trunk diseases. The shear force was measured using a force plate. A comfortable sitting posture in the experimental chair was selected for measurement. The rotational axis was positioned 13 cm forward on the horizontal plane from the intersection between the seat and the back support. The axis positions on the vertical plane as two experimental conditions were the seat height and the 7.5-cm upward from the seat height which was nearer to the hip joint. RESULTS: In returning the back support to an upright position, the horizontal force was 12.4 ± 1.6 (percent body weight) under the seat height-axis condition and 10.1 ± 1.8 (percent body weight) under the upward-axis condition (p < 0.01). CONCLUSION: This result suggested that the wheelchair might have to be capable of adjusting the height of the rotational axis of the back support to reduce the horizontal force applied to buttocks. CLINICAL RELEVANCE: This study shows one of the suggestions regarding seating approach for the prevention of decubitus ulcers. There is a possibility of reducing horizontal force applied to buttocks after reclined back support, by adjusting the height of the rotational axis position of wheelchair back support.

Correlation between Peak Expiratory Flow and Abdominal Muscle Thickness.

[Purpose] The purpose of this study was to determine whether forced expiration is correlated with abdominal muscle thickness. [Subjects] Twenty-three healthy male volunteers participated in this study. [Methods] The peak expiratory flow (PEF) was obtained using a peak flow meter with subjects in the sitting position. The thicknesses of the right rectus abdominis, external oblique, internal oblique, and transverse abdominis muscles were measured using B-mode ultrasonography at the end of a relaxed expiration in the supine position. [Results] Among the abdominal muscles, only the thickness of the external oblique muscle displayed a significant correlation with PEF. [Conclusion] It appears that the thickness of the external oblique muscle might be associated with PEF during forced expiration.

Influence of Hip Joint Position on Muscle Activity during Prone Hip Extension with Knee Flexion.

[Purpose] This study investigated the selective activation of the gluteus maximus during a prone hip extension with knee flexion exercise, with the hip joint in different positions. [Subjects] The subjects were 21 healthy, male volunteers. [Methods] Activities of the right gluteus maximus, right hamstrings, bilateral lumbar erector spinae, and bilateral lumbar multifidus were measured using surface electromyography during a prone hip extension with knee flexion exercise. Measurements were made with the hip joint in each of 3 positions: (1) a neutral hip joint position, (2) an abduction hip joint position, and (3) an abduction with external rotation hip joint position. [Results] Gluteus maximus activity was significantly higher when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. Gluteus maximus activity was also significantly higher in the abduction hip joint position than in the neutral hip joint position. Hamstring activity was significantly lower when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. [Conclusion] Abduction and external rotation of the hip during prone hip extension with knee flexion exercise selectively activates the gluteus maximus.