In vivo hip joint loads and pedal forces during ergometer cycling

The rising prevalence of osteoarthritis and an increase in total hip replacements calls for attention to potential therapeutic activities. Cycling is considered as a low impact exercise for the hip joint and hence recommended. However, there are limited data about hip joint loading to support this claim. The aim of this study was to measure synchronously the in vivo hip joint loads and pedal forces during cycling. The in vivo hip joint loads were measured in 5 patients with instrumented hip implants. Data were collected at several combinations of power and cadence, at two saddle heights.Joint loads and pedal forces showed strong linear correlation with power. So the relationship between the external pedal forces and internal joint forces was shown. While cycling at different cadences the minimum joint loads were acquired at 60 RPM. The lower saddle height configuration results in an approximately 15% increase compared to normal saddle height.The results offered new insights into the actual effects of cycling on the hip joint and can serve as useful tools while developing an optimum cycling regimen for individuals with coxarthrosis or following total hip arthroplasty. Due to the relatively low contact forces, cycling at a moderate power level of 90 W at a normal saddle height is suitable for patients.     

Electromyographic analysis of rectus femoris activity during seated to standing position and walking in water and on dry land in healthy children and children with cerebral palsy

Purpose: To analyze rectus femoris activity during seated to standing position and walking in water and on dry land comparing a group of children with the spastic diparesis type of cerebral palsy (CP) and a group of children without neurological disorders. Methods: This study included a group of nine children with CP and a control group of 11 children. The study compared the electromyographic activity of the rectus femoris during seated to standing position and walking, in water and on land. Results: A greater activation of the rectus femoris was observed in the group of children with CP compared with the control group when moving from a seated position to a standing position in water (p = 0.0039) and while walking on land (p = 0.0014) or in the pool (p = 0.007). Conclusion: This study demonstrated the activation of the rectus femoris while walking or standing up from a seated position in water was greater in the group of children with CP. Further studies should be performed to better understand the extent of muscular activation during body immersion in individuals with neurological disorders.     

Endurance and strength training effects on physiological and muscular parameters during prolonged cycling

PurposeThis study investigated the effects of a combined endurance and strength training on the physiological and neuromuscular parameters during a 2-h cycling test.MethodsFourteen triathletes were assigned to an endurance-strength training group and an endurance-only training group. They performed three experimental trials before and after training: an incremental cycling test to exhaustion, a maximal concentric lower-limbs strength measurement and a 2-h cycling exercise. Physiological parameters, free cycling chosen cadence and the EMG of Vastus Lateralis (VL) and Rectus Femoris (RF) were analysed during the 2-h cycling task before and after a strength training programme of 5 weeks (three times per week).ResultsThe results showed that the maximum strength and the isometric maximal voluntary contraction (isoMVC) after training were significantly higher (P < 0.01) and lower (P < 0.01) than those before training, respectively, in endurance-strength training group and endurance-only group. The physiological variables measured during the cycling tests and the progressive increase (P < 0.01) in EMGi_(VL) and EMGi_(RF) throughout the 2-h cycling test did not differ between the two groups before and after training, except for the variation of EMGi_(VL) over the cycle time which was stabilized during the second hour of the 2-h cycling test due to training in endurance-strength training group. The decrease in free cycling chosen cadence observed in pre-training (P < 0.01) was also replaced by a steady free cycling chosen cadence for the endurance-strength training group during the second hour of exercise.ConclusionThis study confirmed the decrease in the free cycling chosen cadence with exercise duration and demonstrated that a specific combined endurance and strength training can prevent this decrease during a 2-h constant cycling exercise.     

Effect of changes in orientation and position of external loads on trunk muscle activity and kinematics in upright standing

Forces at different heights and orientations are often carried by hands while performing occupational tasks. Trunk muscle activity and spinal loads are likely dependent on not only moments but also the orientation and height of these forces. Here, we measured trunk kinematics and select superficial muscle activity of 12 asymptomatic subjects while supporting forces in hands in upright standing. Magnitude of forces in 5 orientations (−25°, 0°, 25°, 50° and 90°) and 2 heights (20 cm and 40 cm) were adjusted to generate flexion moments of 15, 30 and 45 N m at the L5-S1 disc centre. External forces were of much greater magnitude when applied at lower elevation or oriented upward at 25°. Spinal kinematics remained nearly unchanged in various tasks.Changes in orientation and elevation of external forces substantially influenced the recorded EMG, despite similar trunk posture and identical moments at the L5-S1. Greater EMG activity was overall recorded under larger forces albeit constant moment. Increases in the external moment at the L5-S1 substantially increased EMG in extensor muscles (p < 0.001) but had little effect on abdominals; e.g., mean longissimus EMG for all orientations increased by 38% and 75% as the moment level altered from 15 N m to 30 N m and to 45 N m while that in the rectus abdominus increased only by 2% and 4%, respectively. Under 45 N m moment and as the load orientation altered from 90° to 50°, 25°, 0° and −25°, mean EMG dropped by 3%, 12%, 12% and 1% in back muscles and by 17%, 17%, 19% and 13% in abdominals, respectively. As the load elevation increased from 20 cm to 40 cm, mean EMG under maximum moment decreased by 21% in back muscles and by 17% in abdominals.Due to the lack of EMG recording of deep lumbar muscles, changes in relative shear/compression components and different net moments at cranial discs despite identical moments at the caudal L5-S1 disc, complementary model studies are essential for a better comprehension of neuromuscular strategies in response to alterations in load height and orientation.     

Timing of muscle activation of the lower limbs can be modulated to maintain a constant pedaling cadence

This study investigated changes in muscle activity when subjects are asked to maintain a constant cadence during an unloaded condition. Eleven subjects pedaled for five loaded conditions (220 W, 190 W, 160 W, 130 W, 100 W) and one unloaded condition at 80 rpm. Electromyographic (EMG) activity of six lower limb muscles, pedal forces and oxygen consumption were calculated for every condition. Muscle activity was defined by timing (EMG onset and offset) and level (integrated values of EMGrms calculated between EMG onset and EMG offset) of activation, while horizontal and vertical impulses were computed to characterize pedal forces. Muscle activity, pedal forces and oxygen consumption variables measured during the unloaded condition were compared with those extrapolated to 0 W from the loaded conditions, assuming a linear relationship. The muscle activity was changed during unloaded condition: EMG onset and/or offset of rectus femoris, biceps femoris, vastus medialis, and gluteus maximus muscles were delayed (p < 0.05); iEMGrms values of rectus femoris, biceps femoris, gastrocnemius medialis and tibialis anterior muscles were higher than those extrapolated to 0 W (p < 0.05). Vertical impulse over the extension phase was lower (p < 0.05) while backward horizontal impulse was higher (p < 0.05) during unloaded condition than those extrapolated to 0 W. Oxygen consumptions were higher during unloaded condition than extrapolated to 0W (750 ± 147 vs. 529 ± 297 mLO₂.min^?1; p < 0.05). Timing of activation of rectus femoris and biceps femoris was dramatically modified to optimize pedal forces and maintain a constant cadence, while systematic changes in the activation level of the bi-articular muscles induced a relative increase in metabolic expenditure when pedaling during an unloaded condition.     

The influence of seat height on the mechanical function of the triceps surae muscles during steady-rate cycling

The purpose of this study was to manipulate bicycle seat height in order to perturbate muscle length, contraction velocity and excitation of soleus and medial gastrocnemius muscles. One group of female riders (n = 13) rode a stationary ergometer at 200 W and a cadence of 80 rpm. Individuals rode at a self-selected seat height, a 10% lowered and 5% raised seat position. It was hypothesized that because the two muscles would operate at decreased contraction velocities at the low seat, the integrated EMG would be less for the lowest seat position. The soleus and medial gastrocnemius muscles showed a significant decrease in integrated EMG value with decreased seat height (soleus F_2,24 = 5.4, p < 0.01, gastrocnemius F_2,24 = 51.6, p < 0.0001). The combined effect of the movement at the ankle and knee joints resulted in increased length of gastrocnemius rather than shortening at the lowered seat-height position as anticipated. This suggested that there was a greater role of knee-joint angle in determining the muscle excitation for medial gastrocnemius. The original hypothesis was accepted, confirming the importance of setting proper seat height.     

Alternating stimulation of synergistic muscles during functional electrical stimulation cycling improves endurance in persons with spinal cord injury

Therapeutic effects of functional electrical stimulation (FES) cycling for persons with spinal cord injury (SCI) are limited by high rates of muscular fatigue. FES-cycling performance limits and surface mechanomyography (MMG) of 12 persons with SCI were compared under two different stimulation protocols of the quadriceps muscles. One strategy used the standard “co-activation” protocol from the manufacturer of the FES cycle which involved intermittent simultaneous activation of the entire quadriceps muscle group for 400 ms. The other strategy was an “alternation” stimulation protocol which involved alternately stimulating the rectus femoris (RF) muscle for 100 ms and the vastus medialis (VM) and vastus lateralis (VL) muscles for 100 ms, with two sets with a 400 ms burst. Thus, during the alternation protocol, each of the muscle groups rested for two 100 ms “off” periods in each 400 ms burst. There was no difference in average cycling cadence (28 RPM) between the two protocols. The alternation stimulation protocol produced longer ride times and longer virtual distances traveled and used lower stimulation intensity levels with no differences in average MMG amplitudes compared to the co-activation protocol. These results demonstrate that FES-cycling performance can be enhanced by a synergistic muscle alternation stimulation strategy.     

The impact of localized fatigue on contralateral tremor and muscle activity is exacerbated by standing posture

Physiological tremor is an inherent feature of the motor system that is influenced by intrinsic (neuromuscular) and/or extrinsic (task) factors. Given that tremor must be accounted for during the performance of many fine motor skills; there is a requirement to clarify how different factors interact to influence tremor. This study was designed to assess the impact localized fatigue of a single arm and stance position had on bilateral physiological tremor and forearm muscle activity. Results demonstrated that unilateral fatigue produced bilateral increases in tremor and wrist extensor activity. For example, fatigue resulted in increases in extensor activity across both exercised (increased 8–10% MVC) and the non-exercised arm (increased 3–7% MVC). The impact of fatigue was not restricted to changes in tremor/EMG amplitude, with altered hand–finger coupling observed within both arms. Within the exercised arm, cross-correlation values decreased (pre-exercise r = 0.62–0.64; post-exercise r = 0.37–0.43) while coupling increased within the non-exercised arm (pre-exercise r = 0.51–0.55; post-exercise r = 0.62–0.67). While standing posture alone had no significant impact on tremor/EMG dynamics, the tremor and muscle increases seen with fatigue were more pronounced when standing. Together these results demonstrate that the combination of postural and fatigue factors can influence both tremor/EMG outputs and the underlying coordinative coupling dynamics.     

The impact of altered task mechanics on timing and duration of eccentric bi-articular muscle contractions during cycling

In order to understand muscle adaptations to altered task mechanics during cycling, this study investigated the impact of altered seat height and cadence on timing and duration of gastrocnemius (GAST), biceps femoris (BF) and vastus lateralis (VL) eccentric contractions and muscle activation patterns, and cycling economy. Ten male cyclists completed 9 × 5 min of cycling at 3 seat heights and 3 cadences. Three-dimensional leg kinematics and muscle activation patterns were recorded to estimate timing of eccentric muscle contractions. Onset, offset and duration of eccentric contractions and, onset, offset and duration of muscle activation were calculated, along with cycling economy. Duration of GAST and VL eccentric contractions decreased with increasing seat height due to earlier offset of eccentric muscle contractions. Duration of BF eccentric contractions significantly increased with seat height due to a later eccentric contraction offset. Offset of GAST and BF muscle activation occurred earlier with increasing cadence. Cycling economy was significantly affected by cadence but not seat height. The results suggest that as a consequence of altered seat height, proprioceptive feedback is used to fine-tune the timing of bi-articular eccentric muscle contractions. These results may have implications for seat height self-selection.     

Lower limb dynamics change for children while walking with backpack loads to modulate shock transmission to the head

Backpack load carriage increases ground reaction forces and increases the stiffness in the upper extremity that can cause transmission of higher amount of forces from the lower extremity to the head. This study investigated the effect of load carriage and placement of load on the back on the shock transmission mechanisms amongst children. Fifteen primary school boys with mean age 10.01 (±1.31) years, mean height 136.40 (±10.08) cm and mean mass 31.83 (±7.13) kg completed the study. Subjects carried 10%, 15% and 20% bodyweight (BW) loads on two locations on the back, namely upper and lower. Results showed a significant reduction in pelvic and trunk rotation in the transverse plane and an increase in the upper body stiffness for loads exceeding 15% of BW. The lower limb results showed a reduction in the first peak force and cadence and a significant change in the walking velocity and time to the first peak force for 20% load. No significant differences were found for the load configuration but the upper configuration showed slightly higher shock transmission. The changes in the lower limb dynamics indicated that there are locomotion mechanisms in place amongst children to modulate shock transmission to the head.     

Spatial reorganisation of muscle activity correlates with change in tangential force variability during isometric contractions

The aim of this study was to quantify the effects of spatial reorganisation of muscle activity on task-related and tangential components of force variability during sustained contractions. Three-dimensional forces were measured from isometric elbow flexion during submaximal contractions (50 s, 5–50% of maximal voluntary contraction (MVC)) and total excursion of the centre of pressure was extracted. Spatial electromyographic (EMG) activity was recorded from the biceps brachii muscle. The centroids of the root mean square (RMS) EMG and normalised mutual information (NMI) maps were computed to assess spatial muscle activity and spatial relationship between EMG and task-related force variability, respectively. Result showed that difference between the position of the centroids at the beginning and at the end of the contraction of the RMS EMG and the NMI maps were different in the medial–lateral direction (P < 0.05), reflecting that muscle regions modulate their activity without necessarily modulating the contribution to the task-related force variability over time. Moreover, this difference between shifts of the centroids was positively correlated with the total excursion of the centre of pressure at the higher levels of contractions (>30% MVC, R² > 0.30, P < 0.05), suggesting that changes in spatial muscle activity could impact on the modulation of tangential forces. Therefore, within-muscle adaptations do not necessarily increase force variability, and this interaction can be quantified by analysing the RMS EMG and the NMI map centroids.     

Epoch length to accurately estimate the amplitude of interference EMG is likely the result of unavoidable amplitude cancellation

Researchers and clinicians routinely rely on interference electromyograms (EMGs) to estimate muscle forces and command signals in the neuromuscular system (e.g., amplitude, timing, and frequency content). The amplitude cancellation intrinsic to interference EMG, however, raises important questions about how to optimize these estimates. For example, what should the length of the epoch (time window) be to average an EMG signal to reliably estimate muscle forces and command signals? Shorter epochs are most practical, and significant reductions in epoch have been reported with high-pass filtering and whitening. Given that this processing attenuates power at frequencies of interest (<250 Hz), however, it is unclear how it improves the extraction of physiologically relevant information. We examined the influence of amplitude cancellation and high-pass filtering on the epoch necessary to accurately estimate the “true” average EMG amplitude calculated from a 28 s EMG trace (EMG_ref) during simulated constant isometric conditions. Monte Carlo iterations of a motor-unit model simulating 28 s of surface EMG produced 245 simulations under two conditions: with and without amplitude cancellation. For each simulation, we calculated the epoch necessary to generate average full-wave rectified EMG amplitudes that settled within 5% of EMGref. For the no-cancellation EMG, the necessary epochs were short (e.g., <100 ms). For the more realistic interference EMG (i.e., cancellation condition), epochs shortened dramatically after using high-pass filter cutoffs above 250 Hz, producing epochs short enough to be practical (i.e., <500 ms). We conclude that the need to use long epochs to accurately estimate EMG amplitude is likely the result of unavoidable amplitude cancellation, which helps to clarify why high-pass filtering (>250 Hz) improves EMG estimates.     

The effects of cycling cadence on the phases of joint power,crank power,force and force effectiveness

We examined the influence of cadence in cycling technique by quantifying phase relationships for a number of important variables at the crank and lower extremity joints. Any difference in the effect of cadence on force, effectiveness, and power phases would indicate an essential change in coordination pattern. Cycle kinetics was recorded for 10 male competitive cyclists at five cadences (60–100 rpm) at submaximal load (260 W). Joint powers were calculated using inverse dynamics methods. All data were expressed as a function of crank position. The phase of the crank mechanical profiles (total force, crank and joint power, and effectiveness) was calculated using four methods: crank angle of maximum (MA) and minimum (MI), fitting a sine wave (SI) and by cross-correlation (XC). These methods, apart from the MA method, showed the same relative phase. The variables, however, showed different phases being expressed as time lag: force effectiveness: 0.131 (±0.034) s; total force: 0.149 (±0.021) s; power: 0.098 (±0.027) s. The phases in joint powers hip 0.071 (±0.008), knee 0.082 (±0.009), and hip 0.077 (±0.012) were only well described by XC, and were somewhat lower than the crank power phase. These differences indicate the potential effect of inertia of the lower limb in phase shifts from joints to crank. Furthermore, the differences between the various crank variables indicate a change of technique with cadence.     

Effect of seat positions on discomfort,muscle activation,pressure distribution and pedal force during cycling

The aim of this study was to measure and analyse discomfort and biomechanics of cycling, i.e., muscle activation, centre of pressure of seat pressure profiles and pedal forces as a function of seat position. Twenty-one recreationally active individuals cycled for 10 min at 100 W on an ergometer cycle using five different seat positions. The neutral position was considered as basic seat position and was compared with upward, downward, forward and backward seat positions. The initial bout was repeated at the end of the recording session. Discomfort increased for upward and backward condition compared with neutral (P < 0.05). Normalized surface electromyography from gastrocnemius decreased in the downward and forward position but increased in the upward and backward position. The minimum force became less negative for forward position compared with neutral seat position (P < 0.05). The degree of variability of centre of pressure increased in the upward and backward position and the entropy of the centre of pressure of sitting posture for backward position decreased compared with neutral seat position (P < 0.05). The present study revealed that consecutive changes of seat position over time lead to increase in discomfort as well as alterations of the biomechanics of cycling.     

Intra-operatively measured spastic semimembranosus forces of children with cerebral palsy

The knee kept forcibly in a flexed position is typical in cerebral palsy. Using a benchmark, we investigate intra-operatively if peak spastic hamstring force is measured in flexed knee positions. This tests the assumed shift of optimal length due to adaptation of spastic muscle and a decreasing force trend towards extension. Previously we measured spastic gracilis (GRA) and semitendinosus (ST) forces. Presently, we studied spastic semimembranosus (SM) and tested the following hypotheses: spastic SM forces are (1) high in flexed and (2) low in extended positions. We compared the data to those of GRA and ST to test (3) if percentages of peak force produced in flexed positions are different. During muscle lengthening surgery of 8 CP patients (9 years, 4 months; GMFCS levels = II–IV; limbs tested = 13) isometric SM forces were measured from flexion (120°) to full extension (0°). Spastic SM forces were low in flexed knee positions (only 4.2% (3.4%) and 10.7% (9.7%) of peak force at KA = 120° and KA = 90° respectively, indicating less force production compared to the GRA or ST) and high in extended knee positions (even 100% of peak force at KA = 0°). This indicates an absence of strong evidence for a shift of optimal muscle length of SM towards flexion.     

Effect of instruction,surface stability,and load intensity on trunk muscle activity

The aim of this study was to assess the effect of verbal instruction, surface stability, and load intensity on trunk muscle activity levels during the free weight squat exercise. Twelve trained males performed a free weight squat under four conditions: (1) standing on stable ground lifting 50% of their 1-repetition maximum (RM), (2) standing on a BOSU balance trainer lifting 50% of their 1-RM, (3) standing on stable ground lifting 75% of their 1-RM, and (4) receiving verbal instructions to activate the trunk muscles followed by lifting 50% of their 1-RM. Surface EMG activity from muscles rectus abdominis (RA), external oblique (EO), transversus abdominis/internal oblique (TA/IO), and erector spinae (ES) were recorded for each condition and normalized for comparisons. Muscles RA, EO, and TA/IO displayed greater peak activity (39–167%) during squats with instructions compared to the other squat conditions (P = 0.04–0.007). Peak EMG activity of muscle ES was greater for the 75% 1-RM condition than squats with instructions or lifting 50% of 1-RM (P = 0.04–0.02). The results indicate that if the goal is to enhance EMG activity of the abdominal muscles during a multi-joint squat exercise then verbal instructions may be more effective than increasing load intensity or lifting on an unstable surface. However, in light of other research, conscious co-activation of the trunk muscles during the squat exercise may lead to spinal instability and hazardous compression forces in the lumbar spine.     

EMG normalization to study muscle activation in cycling

The value of electromyography (EMG) is sensitive to many physiological and non-physiological factors. The purpose of the present study was to determine if the torque–velocity test (T–V) can be used to normalize EMG signals into a framework of biological significance. Peak EMG amplitude of gluteus maximus (GMAX), vastus lateralis (VL), rectus femoris (RF), biceps femoris long head (BF), gastrocnemius medialis (GAS) and soleus (SOL) was calculated for nine subjects during isometric maximal voluntary contractions (IMVC) and torque–velocity bicycling tests (T–V). Then, the reference EMG signals obtained from IMVC and T–V bicycling tests were used to normalize the amplitude of the EMG signals collected for 15 different submaximal pedaling conditions. The results of this study showed that the repeatability of the measurements between IMVC (from 10% to 23%) and T–V (from 8% to 20%) was comparable. The amplitude of the peak EMG of VL was 99 ± 43% higher (p < 0.001) when measured during T–V. Moreover, the inter-individual variability of the EMG patterns calculated for submaximal cycling exercises differed significantly when using T–V bicycling normalization method (GMAX: 0.33 ± 0.16 vs. 1.09 ± 0.04, VL: 0.07 ± 0.02 vs. 0.64 ± 0.14, SOL: 0.07 ± 0.03 vs. 1.00 ± 0.07, RF: 1.21 ± 0.20 vs. 0.92 ± 0.13, BF: 1.47 ± 0.47 vs. 0.84 ± 0.11). It was concluded that T–V bicycling test offers the advantage to be less time and energy-consuming and to be as repeatable as IMVC tests to measure peak EMG amplitude. Furthermore, this normalization method avoids the impact of non-physiological factors on the amplitude of the EMG signals so that it allows quantifying better the activation level of lower limb muscles and the variability of the EMG patterns during submaximal bicycling exercises.     

Intra-session and inter-day reliability of forearm surface EMG during varying hand grip forces

Surface electromyography (EMG) is widely used to evaluate forearm muscle function and predict hand grip forces; however, there is a lack of literature on its intra-session and inter-day reliability. The aim of this study was to determine reliability of surface EMG of finger and wrist flexor muscles across varying grip forces. Surface EMG was measured from six forearm flexor muscles of 23 healthy adults. Eleven of these subjects undertook inter-day test–retest. Six repetitions of five randomized isometric grip forces between 0% and 80% of maximum force (MVC) were recorded and normalized to MVC. Intra- and inter-day reliability were calculated through the intraclass correlation coefficient (ICC) and standard error of measurement (SEM).Normalized EMG produced excellent intra-session ICC of 0.90 when repeated measurements were averaged. Intra-session SEM was low at low grip forces, however, corresponding normalized SEM was high (23–45%) due to the small magnitude of EMG signals. This may limit the ability to evaluate finer forearm muscle function and hand grip forces in daily tasks. Combining EMG of functionally related muscles improved intra-session SEM, improving within-subject reliability without taking multiple measurements. Removing and replacing electrodes inter-day produced poor ICC (ICC < 0.50) but did not substantially affect SEM.     

Intramuscular fine-wire electromyography during cycling: Repeatability,normalisation and a comparison to surface electromyography

This study investigated (a) the feasibility and repeatability of intramuscular fine-wire electromyographic (fEMG) recordings from leg muscles during the repetitive, high-velocity cycling movement, (b) the influence of amplitude normalization technique on repeatability and statistical sensitivity, (c) the influence of test-retest interval duration on repeatability, and (d) differences between fEMG and surface EMG (sEMG) recordings of cycling. EMG activity of leg muscles was recorded using surface and fine-wire electrodes during one (n = 12, to investigate statistical sensitivity and compare sEMG and fEMG) or two sessions (T1 and T2, 5–20 days apart, n = 10, to investigate repeatability). fEMG recordings were feasible and there was high repeatability of fEMG recordings normalised to maximum measured EMG amplitude (MAX); mean coefficients of multiple correlation (CMC) ranged from .83 ± .13 to .88 ± .07. Data normalised to maximal (MVC) or submaximal contractions (sMVC) were less repeatable (p < .01). Statistical sensitivity was also greatest for data normalised to MAX (p < .01). Repeatability of fEMG increased with greater test-retest intervals (p < .01). The global pattern of muscle recruitment was consistent between sEMG and fEMG but sEMG recordings were characterized by additional myoelectric content. These findings support and guide the use of fEMG techniques to investigate leg muscle recruitment during cycling.     

Effects of the pelvic compression belt on gluteus medius,quadratus lumborum,and lumbar multifidus activities during side-lying hip abduction

The aims of this study were to assess the effect of the pelvic compression belt on the electromyographic (EMG) activities of gluteus medius (GM), quadratus lumborum (QL), and lumbar multifidus (LM) during side-lying hip abduction. Thirty-one volunteers (15 men and 16 women) with no history of pathology volunteered for this study. Subjects were instructed to perform hip abduction in side-lying position with and without applying the pelvic compression belt. The pelvic compression belt was adjusted just below the anterior superior iliac spines with the stabilizing pressure using elastic compression bands. Surface EMG data were collected from the GM, QL, and LM of the dominant limb. Significantly decreased EMG activity in the QL (without the pelvic compression belt, 60.19 ± 23.66% maximal voluntary isometric contraction [MVIC]; with the pelvic compression belt, 51.44 ± 23.00% MVIC) and significantly increased EMG activity in the GM (without the pelvic compression belt, 26.71 ± 12.88% MVIC; with the pelvic compression belt, 35.02 ± 18.28% MVIC) and in the LM (without the pelvic compression belt, 30.28 ± 14.60% MVIC; with the pelvic compression belt, 37.47 ± 18.94% MVIC) were found when the pelvic compression belt was applied (p < 0.05). However, there were no significant differences of the EMG activity between male and female subjects. The findings suggest that the pelvic compression belt may be helpful to prevent unwanted substitution movement during side-lying hip abduction, through increasing the GM and LM and decreasing the QL.