In-cheol Jeon

Lower Extremity Strength and the Range of Motion in Relation to Squat Depth

Abstract The purpose of this study was to determine which variables of the range of motion (ROM) and strength of the hip, and ankle are associated with squat depth. In total, 101 healthy subjects (64 males, 37 females) participated in the study. Outcome measures consisted of the ROM of hip flexion, hip internal rotation, external rotation, ankle dorsiflexion with an extended and flexed knee joint, and strength of the hip flexor and ankle dorsiflexor. Squat depth was measured using SIMI motion analysis software. Pearson correlation was used to determine the relationship between variables and squat depth. Multiple stepwise regression analysis was performed to determine variables associated with squat depth. The multiple regression model indicated that ankle dorsiflexion with a flexed knee and the hip flexion ROM were significantly associated with squat depth in male subjects (R2 = 0.435) and ankle dorsiflexion with an extended knee and dorsiflexor strength were significantly associated with squat depth in female subjects (R2 = 0.324). Thus, exercises to increase the ROM of the ankle dorsiflexion, hip flexion, and dorsiflexor strength can be recommended to improve squat performance. Future studies should assess an increased ROM of the ankle dorsiflexion, hip flexion, or dorsiflexor strength effect on deep squat performance.

Ankle-Dorsiflexion Range of Motion After Ankle Self-Stretching Using a Strap

CONTEXT A variety of ankle self-stretching exercises have been recommended to improve ankle-dorsiflexion range of motion (DFROM) in individuals with limited ankle dorsiflexion. A strap can be applied to stabilize the talus and facilitate anterior glide of the distal tibia at the talocrural joint during ankle self-stretching exercises. Novel ankle self-stretching using a strap (SSS) may be a useful method of improving ankle DFROM. OBJECTIVE To compare the effects of 2 ankle-stretching techniques (static stretching versus SSS) on ankle DFROM. DESIGN Randomized controlled clinical trial. SETTING University research laboratory. PATIENTS OR OTHER PARTICIPANTS Thirty-two participants with limited active dorsiflexion (<20°) while sitting (14 women and 18 men) were recruited. MAIN OUTCOME MEASURE(S) The participants performed 2 ankle self-stretching techniques (static stretching and SSS) for 3 weeks. Active DFROM (ADFROM), passive DFROM (PDFROM), and the lunge angle were measured. An independent t test was used to compare the improvements in these values before and after the 2 stretching interventions. The level of statistical significance was set at α = .05. RESULTS Active DFROM and PDFROM were greater in both stretching groups after the 3-week interventions. However, ADFROM, PDFROM, and the lunge angle were greater in the SSS group than in the static-stretching group (P < .05). CONCLUSIONS Ankle SSS is recommended to improve ADFROM, PDFROM, and the lunge angle in individuals with limited DFROM.

Effect of Humeral Elevation Angle on Electromyographic Activity in the Serratus Anterior During the Push-up Plus Exercise.

CONTEXT The push-up-plus (PP) exercise has been recommended for strengthening of the serratus anterior (SA). Previous studies have investigated the effect of different stability properties of the base of support to adjust the difficulty level of SA muscle-strengthening exercises in the PP position. However, the optimal humeral-elevation angle (HEA) for selective activation and maximum contraction of the SA during PP has not been investigated. OBJECTIVES To assess the effects of HEA during PP on electromyographic (EMG) activity in the SA, upper trapezius (UT), and pectoralis major (PM) and on the UT:SA and PM:SA activity ratios. DESIGN Comparative, repeated-measures design. SETTING University research laboratory. PARTICIPANTS 29 healthy men. MAIN OUTCOME MEASURES The subjects performed PP at 3 different HEAs (60°, 90°, and 120°); EMG activity in the SA, UT, and PM was measured, and the UT:SA and PM:SA activity ratios were calculated. Differences in muscle activity and ratios between the 60°, 90°, and 120° HEAs were assessed using 1-way repeated-measures analysis of variance; the Bonferroni correction was applied. RESULTS SA muscle activity was significantly increased, in order of magnitude, at the 120°, 90°, and 60° HEAs. UT:SA and PM:SA activity ratios were significantly greater during performance of the PP at an HEA of 60° than at HEAs of 120° and 90°. CONCLUSION The results suggest that an HEA of 120° should be used during performance of the PP because it produces greater SA activation than HEAs of 60° and 90°.

Effect of treadmill walking with ankle stretching orthosis on ankle flexibility and gait.

[Purpose] The purpose of this study was to evaluate the kinematics of the ankle in the lunge to estabilish effectiveness of an ankle stretching orthosis (ASO) on the ankle dorsiflexion range of motion (ROM) of individuals with limited dorsiflexion ROM. [Subjects and Methods] Forty ankles with decreased dorsiflexion ROM of 20 participants were evaluated in this study. After wearing the ASO, participants walked on a treadmill for 15 minutes. Participants walked on the treadmill at a self-selected comfortable speed. Ankle dorsiflexion ROM, maximum dorsiflexion ROM before heel-off, and time to heel-off during the stance phase of gait were measured before and after 15 minutes of treadmill walking with the ASO. The differences in all variables between before and after treadmill walking with ASO were analyzed using the paired t-test. [Results] Ankle active and passive ROM, and dorsiflexion ROM during lunge increased significantly after treadmill walking with ASO. Treadmill walking with the ASO significantly increased the angle of maximal dorsiflexion before heel-off and time to heel-off during the stance phase. [Conclusion] The results of this study show that treadmill walking with the ASO effectively improved ankle flexibility and restored the normal gait pattern of the ankle joint by increasing dorsiflexion ROM, maximal angle of dorsiflexion, and time to heel-off in the stance phase.

The effects of surface condition on abdominal muscle activity during single-legged hold exercise

To treat low-back pain, various spinal stability exercises are commonly used to improve trunk muscle function and strength. Because human movement for normal daily activity occurs in multi-dimensions, the importance of exercise in multi-dimensions or on unstable surfaces has been emphasized. Recently, a motorized rotating platform (MRP) for facilitating multi-dimensions dynamic movement was introduced for clinical use. However, the abdominal muscle activity with this device has not been reported. The purpose of this study was to compare the abdominal muscle activity (rectus abdominis, external and internal oblique muscles) during an active single-leg-hold (SLH) exercise on a floor (stable surface), foam roll, and motorized rotating platform (MRP). Thirteen healthy male subjects participated in this study. Using electromyography, the abdominal muscle activity was measured while the subjects performed SLH exercises on floor (stable surface), foam roll, and MRP. There were significant differences in the abdominal muscle activities among conditions (P<.05), except for left EO (P>.05) (Fig. 2). After the Bonferroni correction, however, no significant differences among conditions remained, except for differences in both side IO muscle activity between the floor and foam roll conditions (padj<0.017). The findings suggest that performing the SLH exercises on a foam roll and MRP is more effective increased activities of both side of RA and IO, and Rt. EO compared to floor condition. However, there were no significant differences in abdominal muscles activity in the multiple comparison between conditions (mean difference were smaller than the standard deviation in the abdominal muscle activities) (padj>0.017), except for differences in both side IO muscle activity between the floor (stable surface) and foam roll (padj<0.017) (effect size: 0.79/0.62 (non-supporting/supporting leg) for foam-roll versus floor).

Reliability and criterion validity of measurements using a smart phone-based measurement tool for the transverse rotation angle of the pelvis during single-leg lifting

ABSTRACT Objective: The purposes of this study were to determine the intra-rater test–retest reliability of a smart phone-based measurement tool (SBMT) and a three-dimensional (3D) motion analysis system for measuring the transverse rotation angle of the pelvis during single-leg lifting (SLL) and the criterion validity of the transverse rotation angle of the pelvis measurement using SBMT compared with a 3D motion analysis system (3DMAS). Method: Seventeen healthy volunteers performed SLL with their dominant leg without bending the knee until they reached a target placed 20 cm above the table. This study used a 3DMAS, considered the gold standard, to measure the transverse rotation angle of the pelvis to assess the criterion validity of the SBMT measurement. Intra-rater test–retest reliability was determined using the SBMT and 3DMAS using intra-class correlation coefficient (ICC) [3,1] values. The criterion validity of the SBMT was assessed with ICC [3,1] values. Result: Both the 3DMAS (ICC = 0.77) and SBMT (ICC = 0.83) showed excellent intra-rater test–retest reliability in the measurement of the transverse rotation angle of the pelvis during SLL in a supine position. Moreover, the SBMT showed an excellent correlation with the 3DMAS (ICC = 0.99). Conclusion: Measurement of the transverse rotation angle of the pelvis using the SBMT showed excellent reliability and criterion validity compared with the 3DMAS.

An immediate effect of axial neck rotation training with real time visual feedback using a smartphone inclinometer on improvement in axial neck rotation function

ABSTRACT Objectives: The purpose of this study was to compare the immediate effects of axial neck rotation training (Axi-NRT) with and without real-time visual feedback (VF) using a smartphone inclinometer on the range of motion (ROM) for axial neck rotation and the onset of compensatory neck lateral bending and extension during active neck rotation.Methods: Twenty participants with restricted ROM for neck rotation but no neck pain (21.1 ± 1.6 years and 8 males, 12 females) were recruited for Axi-NRT with VF, and twenty age- and gender-matched participants with restricted ROM for neck rotation were recruited for Axi-NRT without VF. Changes in ROM for neck rotation and the onset time of compensatory neck movement during active neck rotation were measured using an electromagnetic tracking system. Results: Axi-NRT with VF was more effective in increasing ROM for neck rotation and decreasing and delaying the onset of compensatory neck movements during active neck rotation compared with Axi-NRT without VF. Conclusions: Repeated Axi-NRT using VF is useful to educate participants in maintaining the axis of the cervical spine and to increase ROM for axial neck rotation with less compensatory neck motion in participants with a restricted range of neck rotations.

Comparison of Hip and Back Muscle Activity and Pelvic Compensation in Healthy Subjects During Three Different Prone Table Hip Extension Exercises

CONTEXT Prone hip extension has been recommended for strengthening the back and hip muscles. Previous studies have investigated prone hip extension conducted with subjects on the floor in the prone position. However, no study has compared 3 different table hip-extension (THE) positions in terms of the activities of the back- and hip-joint muscles with lumbopelvic motion. OBJECTIVE To identify more effective exercises for strengthening the gluteus maximus (GM) by comparing 3 different exercises (THE alone, THE with the abdominal drawing-in maneuver [THEA], and THEA with chair support under the knee [THEAC]) based on electromyographic muscle activity and pelvic compensation. DESIGN Repeated-measure within-subject intervention. SETTING University research laboratory. PARTICIPANTS 16 healthy men. MAIN OUTCOME MEASURES Surface electromyography (EMG) was used to obtain data on the GM, erector spinae (ES), multifidus, biceps femoris (BF), and semitendinosus (ST). Pelvic compensation was monitored using an electromagnetic motion-tracking device. Exertion during each exercise was recorded. Any significant difference in electromyographic muscle activity and pelvic motion among the 3 conditions (THE vs THEA vs THEAC) was assessed using a 1-way repeated-measures analysis of variance (ANOVA) with Bonferroni post hoc test. RESULTS The muscle activities recorded by EMG differed significantly among the 3 exercises (P < .01). GM activity was increased significantly during THEAC (P < .01). There was a significant difference in lumbopelvic kinematics in terms of anterior tilting (F = 19.49, P < .01) and rotation (F= 27.38, P < .01) among the 3 exercises. CONCLUSIONS The THEAC exercise was the most effective for strengthening the GM without overactivity of the ES, BF, and ST muscles and lumbopelvic compensation compared with THE and THEA.

Reliability of ultrasonography measurement for the longus colli according to inward probe pressure

[Purpose] To investigate the intra- and inter-rater reliability of the cross-sectional area (CSA) and muscle thickness (MT) of the longus colli according to the inward pressure of an ultrasonography (US) probe (0.5 and 1 kg). [Subjects] Thirteen subjects (11 males and 2 females; age, 23.1 ± 2.9 years) were recruited via convenience sampling of university students. [Methods] Real-time US measurements of the CSA and MT of the longus colli were recorded. Repeated US measurements using a standard protocol were performed on the same day 1 hour apart to assess intra- and inter-rater reliability. Intra-class correlation coefficients (ICC; 2, 1) were used to determine the intra- and inter-rater reliability of the CSA and MT measurements. [Results] This study demonstrated that the US measurements (0.5 and 1 kg) of the CSA and MT of the longus colli give reliable and consistent results. [Conclusion] Based on these results, a consistent inward pressure of the probe is needed to ensure precise US measurement of the longus colli muscle.