Region‐dependent hamstrings activity in Nordic hamstring exercise and stiff‐leg deadlift defined with high‐density electromyography

Recent studies suggest region‐specific metabolic activity in hamstring muscles during injury prevention exercises, but the neural representation of this phenomenon is unknown. The aim of this study was to examine whether regional differences are evident in the activity of biceps femoris long head (BFlh) and semitendinosus (ST) muscles during two common injury prevention exercises. Twelve male participants without a history of hamstring injury performed the Nordic hamstring exercise (NHE) and stiff‐leg deadlift (SDL) while BFlh and ST activities were recorded with high‐density electromyography (HD‐EMG). Normalized activity was calculated from the distal, middle, and proximal regions in the eccentric phase of each exercise. In NHE, ST overall activity was substantially higher than in BFlh (d  =  1.06 ± 0.45), compared to trivial differences between muscles in SDL (d  =  0.19 ± 0.34). Regional differences were found in NHE for both muscles, with different proximal‐distal patterns: The distal region showed the lowest activity level in ST (regional differences, d range = 0.55‐1.41) but the highest activity level in BFlh (regional differences, d range = 0.38‐1.25). In SDL, regional differences were smaller in both muscles (d range = 0.29‐0.67 and 0.16‐0.63 in ST and BFlh, respectively) than in NHE. The use of HD‐EMG in hamstrings revealed heterogeneous hamstrings activity during typical injury prevention exercises. High‐density EMG might be useful in future studies to provide a comprehensive overview of hamstring muscle activity in other exercises and high‐injury risk tasks.     

Effects of muscle activation on shear between human soleus and gastrocnemius muscles

Lateral connections between muscles provide pathways for myofascial force transmission. To elucidate whether these pathways have functional roles in vivo, we examined whether activation could alter the shear between the soleus (SOL) and lateral gastrocnemius (LG) muscles. We hypothesized that selective activation of LG would decrease the stretch‐induced shear between LG and SOL. Eleven volunteers underwent a series of knee joint manipulations where plantar flexion force, LG, and SOL muscle fascicle lengths and relative displacement of aponeuroses between the muscles were obtained. Data during a passive full range of motion were recorded, followed by 20° knee extension stretches in both passive conditions and with selective electrical stimulation of LG. During active stretch, plantar flexion force was 22% greater (P < 0.05) and relative displacement of aponeuroses was smaller than during passive stretch (P < 0.05). Soleus fascicle length changes did not differ between passive and active stretches but LG fascicles stretched less in the active than passive condition when the stretch began at angles of 70° and 90° of knee flexion (P < 0.05). The activity‐induced decrease in the relative displacement of SOL and LG suggests stronger (stiffer) connectivity between the two muscles, at least at flexed knee joint angles, which may serve to facilitate myofascial force transmission.     

EMG power spectra of intercollegiate athletes and anterior cruciate ligament injury risk in females

PURPOSE: Females have a disproportionately high incidence of anterior cruciate ligament (ACL) injuries compared with males in analogous sports. Although the pathogenesis of this higher frequency has not been elucidated, gender differences in neuromuscular control of the knee may play an important role. This study evaluates EMG power spectra of the quadriceps and hamstring muscles during dynamic, fatiguing exercise to examine differences between male and female intercollegiate athletes. METHODS: Fifty-one collegiate basketball and soccer players (25 female, 26 male) were studied. Maximum voluntary contraction (MVC) was determined for knee flexion and extension. Three consecutive 2-min bouts of isokinetic knee flexion and extension exercise were performed at 40% MVC. EMG activity in the biceps femoris and vastus medialis obliquus was recorded using bipolar surface electrodes. RESULTS: MVC normalized to body weight was significantly greater in males than in females for the quadriceps (P< 0.01). Quadriceps coactivation ratios were significantly higher in females than in males during knee flexion exercises (P< 0.01). CONCLUSIONS: This study demonstrates differences in the EMG power spectra for females when compared with a matched group of males. Increased quadriceps coactivation in females may increase anterior tibial loads under dynamic conditions, thus placing the ACL at higher risk for injury in the female athlete.     

Cardiorespiratory and neuromuscular responses during water aerobics exercise performed with and without equipment

The aim of the study was to compare the cardiorespiratory and neuromuscular responses to water aerobics exercise performed with and without equipment. 15 women performed stationary jogging combined with elbow flexion/extension without equipment, with water-drag forces equipment and with water-floating equipment, at 2 submaximal cadences and at maximal cadence. Heart rate, oxygen uptake and electromyographic signal from biceps brachii, triceps brachii, biceps femoris and rectus femoris were collected during the exercise. The heart rate and oxygen uptake showed significantly higher values during the execution of the water aerobics exercise with either equipment compared to the execution without equipment. In addition, significant difference was found between submaximal cadences. For neuromuscular responses, no significant differences were found between the submaximal cadences for all muscles analyzed; however, significant differences were found between these submaximal cadences and the maximal cadence. Similarly, the results showed no significant differences between the execution of the exercise with or without equipment, except in the muscle activation of triceps brachii and biceps femoris, which was higher when using water-floating and water-drag forces equipment, respectively. In conclusion, the water aerobics exercise presented higher cardiorespiratory responses with equipment and also increased the cadence of execution. Nevertheless, neuromuscular responses were higher only at maximal cadence.     

Heavy‐resistance exercise‐induced increases in jump performance are not explained by changes in neuromuscular function

Post‐activation potentiation (PAP) is the increased involuntary muscle twitch response to stimulation following strong contraction. The enhancement to whole‐body explosive muscular performance (PE) after heavy‐resistance exercise is often attributed to modulations in neuromuscular function that are proposed to reflect PAP, but the evidence to support this is equivocal. We assessed the neuromuscular basis of PE using transcranial magnetic stimulation (TMS) of the primary motor cortex, and electrical stimulation of the femoral nerve. Eleven male athletes performed heavy‐resistance exercise with measures of countermovement jump (CMJ) pre‐ and 8 min post‐exercise. Pre‐exercise and after the final CMJ, single‐ and paired‐pulse TMS were delivered during submaximal isometric knee‐extensor contractions to measure corticospinal excitability, short‐interval intracortical inhibition (SICI), and intracortical facilitation (ICF), with motor evoked potentials recorded from rectus femoris. Twitch responses to motor nerve stimulation during and post maximum‐knee‐extensor contractions were studied to quantify voluntary activation (VA) and potentiated twitch (Q_tw,pot). The experimental protocol successfully induced PE (+4 ± 1% change in CMJ, P = 0.01), but no changes were observed for maximum voluntary force, VA, corticospinal excitability, SICI or ICF (all P > 0.05), and Q_tw,pot declined (P < 0.001). An enhancement of muscular performance after heavy‐resistance exercise was not accompanied by PAP, or changes in measures of neuromuscular function.     

Localization of muscle damage within the quadriceps femoris induced by different types of eccentric exercises

This study examined localization of muscle damage within the quadriceps femoris induced by different types of eccentric exercises by using transverse relaxation time (T ₂)‐weighted magnetic resonance imaging (MRI ). Thirty‐three young males performed either of the following three exercises: single‐joint eccentric contraction of the knee extensors (KE ), eccentric squat (S), or downhill walking (DW ) (n=11/exercise). KE and S consisted of 5‐set×10‐lowering of 90% one‐repetition maximum load. DW was performed for 60 minutes with −10% slope, 6 km/h velocity, and 20% body mass load carried. At pre‐ and 24‐, 48‐, and 72‐hours post‐exercise, T ₂‐MRI was scanned and T ₂ values for the rectus femoris (RF ), vastus intermedius (VI ), vastus lateralis (VL ), and vastus medialis (VM ) at proximal, middle, and distal sites were calculated. Additionally, soreness felt when static pressure was applied to these sites and maximal isometric knee extension torque were measured. Maximal torque significantly (P <.05) decreased (7%‐15%) at 24‐48 hours after all exercises. T ₂ significantly increased (3%‐9%) at 24‐72 hours after all exercises, with heterogeneities within the muscles found in each exercise. Effect size and peak change of T ₂, as well as soreness, overall indicated that the proximal RF after KE and middle VM after S and DW were most affected by these exercises. The VL did not show any significant T ₂ increase after all exercises. These results suggest that muscle damage specifically localizes at the proximal RF by KE and at the middle VM by S and DW , while the VL is least damaged regardless of the exercises.     

Effects of different pedalling techniques on muscle fatigue and mechanical efficiency during prolonged cycling

The present study aimed to test the influence of the pedalling technique on the occurrence of muscular fatigue and on the energetic demand during prolonged constant‐load cycling exercise. Subjects performed two prolonged (45 min) cycling sessions at constant intensity (75% of maximal aerobic power). In a random order, participants cycled either with their preferred technique (PT) during one session or were helped by a visual force‐feedback to modify their pedalling pattern during the other one (FB). Index of pedalling effectiveness was significantly (P<0.05) improved during FB (41.4±5.5%); compared with PT (36.6±4.1%). Prolonged cycling induced a significant reduction of maximal power output, which was greater after PT (?15±9%) than after FB (?7±12%). During steady‐state FB, vastus lateralis muscle activity was significantly (P<0.05) reduced, whereas biceps femoris muscles activities increased compared with PT. Gross efficiency (GE) did not significantly differ between the two sessions, except during the first 15 min of exercise (FB: 19.0±1.9% vs PT: 20.2±1.9%). Although changes in muscular coordination pattern with feedback did not seem to influence GE, it could be mainly responsible for the reduction of muscle fatigue after prolonged cycling.     

Mean arterial pressure following prolonged exercise in the heat: Influence of training status and fluid replacement

Prolonged exercise in the heat without fluid replacement represents a significant challenge to the regulation of mean arterial pressure (MAP). It is unknown, however, if MAP is equally challenged during the post‐exercise period, and whether regular endurance exercise training can provide any benefit to its regulation. We examined MAP (Finometer) in eight trained (T) and eight untrained (UT) individuals prior to, and following, 120 min of cycling at 42 °C with (HYD) and without (DEHY) fluid replacement. Exercise during DEHY induced significant hyperthermia (T: 39.20 ± 0.52 °C vs UT: 38.70 ± 0.36 °C, P = 0.941) and body weight losses (T: 3.4 ± 1.2% vs UT: 2.7 ± 0.9%, P = 0.332), which did not differ between groups. Although MAP was equally reduced 5 min into the post‐exercise period of DEHY (T: ?20 ± 11 mmHg vs UT: ?22 ± 13 mmHg, P = 0.800), its subsequent recovery was significantly different between groups (P = 0.037). While MAP returned to pre‐exercise values in UT (?1 ± 3 mmHg), it remained reduced in T (?9 ± 3 mmHg, P = 0.028). No differences in MAP post‐exercise were observed between groups during HYD. These data suggest that trained men exhibit a greater level of post‐exercise hypotension following prolonged exercise in the heat without fluid replacement. Furthermore, fluid replacement reverses the sustained post‐exercise hypotension observed in trained individuals.     

High‐density electromyography activity in various hamstring exercises

Proximal‐distal differences in muscle activity are rarely considered when defining the activity level of hamstring muscles. The aim of this study was to determine the inter‐muscular and proximal‐distal electromyography (EMG) activity patterns of hamstring muscles during common hamstring exercises. Nineteen amateur athletes without a history of hamstring injury performed 9 exercises, while EMG activity was recorded along the biceps femoris long head (BFlh) and semitendinosus (ST) muscles using 15‐channel high‐density electromyography (HD‐EMG) electrodes. EMG activity levels normalized to those of a maximal voluntary isometric contraction (%MVIC) were determined for the eccentric and concentric phase of each exercise and compared between different muscles and regions (proximal, middle, distal) within each muscle. Straight‐knee bridge, upright hip extension, and leg curls exhibited the highest hamstrings activity in both the eccentric (40%‐54%MVIC) and concentric phases (69%‐85%MVIC). Hip extension was the only BF‐dominant exercise (Cohen's d = 0.28 (eccentric) and 0.33 (concentric)). Within ST, lower distal than middle/proximal activity was found in the bent‐knee bridge and leg curl exercises (d range = 0.53‐1.20), which was not evident in other exercises. BFlh also displayed large regional differences across exercises (d range = 0.00‐1.28). This study demonstrates that inter‐muscular and proximal‐distal activity patterns are exercise‐dependent, and in some exercises are affected by the contraction mode. Knowledge of activity levels and relative activity of hamstring muscles in different exercises may assist exercise selection in hamstring injury management.     

Impact of salbutamol on muscle metabolism assessed by 31P NMR spectroscopy

The potential ergogenic effects of oral salbutamol intake were demonstrated for decades but the underlying mechanisms remain to elucidate. We hypothesized that improved exercise performance after acute oral salbutamol administration is associated with changes in muscle metabolism. Twelve healthy, nonasthmatic, moderately trained, male subjects were recruited to compare in a double‐blind crossover randomized study, an oral dose of salbutamol (4 mg) and a placebo. After treatment administration, subjects performed repetitive plantar flexions to exhaustion in a 3T magnet. Continuous ³¹P nuclear magnetic resonance spectroscopy assessment of the calf muscles was performed at rest, during exercise, and during recovery. No significant difference between treatments was detected in metabolite concentration at rest (P > 0.05). Creatine phosphate and inorganic phosphate changes during and immediately after exercise were similar between treatments (P > 0.05). Intramuscular pH (pHi) was significantly higher at rest, at submaximal exercise but not at exhaustion with salbutamol (pHi at 50% of exercise duration, 6.8 ± 0.1/6.9 ± 0.1 for placebo and salbutamol, respectively, P < 0.05). The maximal power (28 ± 7 W/23 ± 7 W; P = 0.001) and total work (1702 ± 442 J/1381 ± 432 J; P = 0.003) performed during plantar flexions were significantly increased with salbutamol. Salbutamol induced significant improvement in calf muscle endurance with similar metabolic responses during exercise, except slight differences in pHi. Other mechanisms than changes in muscle metabolism may be responsible for the ergogenic effect of salbutamol administration.     

Task‐specific neural adaptations to isoinertial resistance training

This study aimed to delineate the contribution of adaptations in agonist, antagonist, and stabilizer muscle activation to changes in isometric and isoinertial lifting strength after short‐term isoinertial resistance training (RT). Following familiarization, 45 men (23.2 ± 2.8 years) performed maximal isometric and isoinertial strength tests of the elbow flexors of their dominant arms before and after 3 weeks of isoinertial RT. During these tasks, surface electromyography (EMG) amplitude was recorded from the agonist (biceps brachii short and long heads), antagonist (triceps brachii lateral head), and stabilizer (anterior deltoid, pectoralis major) muscles and normalized to either M_max (agonists) or to maximum EMG during relevant reference tasks (antagonist, stabilizers). After training, there was more than a twofold greater increase in training task‐specific isoinertial than isometric strength (17% vs 7%). There were also task‐specific adaptations in agonist EMG, with greater increases during the isoinertial than isometric strength task [analysis of variance (ANOVA), training × task, P = 0.005]. A novel finding of this study was that training increased stabilizer muscle activation during all the elbow flexion strength tasks (P < 0.001), although these were not task‐specific training effects. RT elicited specific neural adaptations to the training task that appeared to explain the greater increase in isoinertial than isometric strength.     

Anterior cruciate ligament injury about 20 years post‐treatment: A kinematic analysis of one‐leg hop

Reduced dynamic knee stability, often evaluated with one‐leg hops (OLHs), is reported after anterior cruciate ligament (ACL) injury. This may lead to long‐standing altered movement patterns, which are less investigated. 3D kinematics during OLH were explored in 70 persons 23 ± 2 years after ACL injury; 33 were treated with physiotherapy in combination with ACL reconstruction (ACL_R) and 37 with physiotherapy alone (ACL_PT). Comparisons were made to 33 matched controls. We analyzed (a) maximal knee joint angles and range of motion (flexion, abduction, rotation); (b) medio‐lateral position of the center of mass (COM) in relation to knee and ankle joint centers, during take‐off and landing phases. Unlike controls, ACL‐injured displayed leg asymmetries: less knee flexion and less internal rotation at take‐off and landing and more lateral COM related to knee and ankle joint of the injured leg at landing. Compared to controls, ACL_R had larger external rotation of the injured leg at landing. ACL_PT showed less knee flexion and larger external rotation at take‐off and landing, and larger knee abduction at Landing. COM was more medial in relation to the knee at take‐off and less laterally placed relative to the ankle at landing. ACL injury results in long‐term kinematic alterations during OLH, which are less evident for ACL_R.     

Muscle activation patterns in the Nordic hamstring exercise: Impact of prior strain injury

This study aimed to determine: (a) the spatial patterns of hamstring activation during the Nordic hamstring exercise (NHE); (b) whether previously injured hamstrings display activation deficits during the NHE; and (c) whether previously injured hamstrings exhibit altered cross‐sectional area (CSA). Ten healthy, recreationally active men with a history of unilateral hamstring strain injury underwent functional magnetic resonance imaging of their thighs before and after six sets of 10 repetitions of the NHE. Transverse (T2) relaxation times of all hamstring muscles [biceps femoris long head (BFlh); biceps femoris short head (BFsh); semitendinosus (ST); semimembranosus (SM)] were measured at rest and immediately after the NHE and CSA was measured at rest. For the uninjured limb, the ST's percentage increase in T2 with exercise was 16.8%, 15.8%, and 20.2% greater than the increases exhibited by the BFlh, BFsh, and SM, respectively (P < 0.002 for all). Previously injured hamstring muscles (n = 10) displayed significantly smaller increases in T2 post‐exercise than the homonymous muscles in the uninjured contralateral limb (mean difference ?7.2%, P = 0.001). No muscles displayed significant between‐limb differences in CSA. During the NHE, the ST is preferentially activated and previously injured hamstring muscles display chronic activation deficits compared with uninjured contralateral muscles.     

Electromyographic activity of the rectus abdominis muscle during exercise performed with the AB Slider

Abstract Strengthening of abdominal muscles is often used in athletic training and in clinical rehabilitation of subjects with low back pain. Traditionally, it is performed by isometric or concentric abdominal contractions in supine position. Recently, the AB Slider has been introduced as a device to train abdominal muscles in quadrupedic position. The aim of this study was to assess the muscle activity and the type of contraction of the rectus abdominis while performing an exercise with the AB Slider and to compare it to a crunch exercise (CE). Sixteen subjects were trained to correctly perform both exercises. Muscle activity of the rectus abdominis was assessed using surface electromyography, and a stereophotogrammetric system Elite was used for the kinematic analysis. During exercise on the AB Slider, knee extension was 51.3°±9.1° (mean±SD) and the distance between the pelvis and the xiphoid process always increased. During CE, rectus abdominis activity was 73.4%±23.5% of the maximal voluntary (MVC) and during the AB Slider exercise it was 96.2%±23.0% of MVC (p=0.011, Wilcoxon’s test). During the exercise with AB Slider, there was greater activation of the rectus abdominis muscle than during CE. Kinematic analysis indicated that the activity occurs in eccentric conditions. The AB Slider seems to be a good device for strengthening the abdominal muscles.     

The biomechanics of running in athletes with previous hamstring injury: A case‐control study

Hamstring injury is prevalent with persistently high reinjury rates. We aim to inform hamstring rehabilitation by exploring the electromyographic and kinematic characteristics of running in athletes with previous hamstring injury. Nine elite male Gaelic games athletes who had returned to sport after hamstring injury and eight closely matched controls sprinted while lower limb kinematics and muscle activity of the previously injured biceps femoris, bilateral gluteus maximus, lumbar erector spinae, rectus femoris, and external oblique were recorded. Intergroup comparisons of muscle activation ratios and kinematics were performed. Previously injured athletes demonstrated significantly reduced biceps femoris muscle activation ratios with respect to ipsilateral gluteus maximus (maximum difference ?12.5%, P = 0.03), ipsilateral erector spinae (maximum difference ?12.5%, P = 0.01), ipsilateral external oblique (maximum difference ?23%, P = 0.01), and contralateral rectus femoris (maximum difference ?22%, P = 0.02) in the late swing phase. We also detected sagittal asymmetry in hip flexion (maximum 8°, P = 0.01), pelvic tilt (maximum 4°, P = 0.02), and medial rotation of the knee (maximum 6°, P = 0.03) effectively putting the hamstrings in a lengthened position just before heel strike. Previous hamstring injury is associated with altered biceps femoris associated muscle activity and potentially injurious kinematics. These deficits should be considered and addressed during rehabilitation.     

Electromyographic and kinematic analysis of cutting maneuvers. Implications for anterior cruciate ligament injury

The objective of this study was to qualitatively characterize quadriceps and hamstring muscle activation as well as to determine knee flexion angle during the eccentric motion of sidestep cutting, cross-cutting, stopping, and landing. Fifteen healthy collegiate and recreational athletes performed the four movements while knee angle and electromyographic activity (surface electrodes) of the vastus lateralis, vastus medialis obliquus, rectus femoris, biceps femoris, and medial hamstring (semimembranosus/semitendinosus) muscles were recorded. The results indicated that there is high-level quadriceps muscle activation beginning just before foot strike and peaking in mid-eccentric motion. In these maneuvers, the level of quadriceps muscle activation exceeded that seen in a maximum isometric contraction. Hamstring muscle activation was submaximal at and after foot strike. The maximum quadriceps muscle activation for all maneuvers was 161% maximum voluntary contraction, while minimum hamstring muscle activity was 14%. Foot strike occurred at an average of 22 degrees of knee flexion for all maneuvers. This low level of hamstring muscle activity and low angle of knee flexion at foot strike and during eccentric contraction, coupled with forces generated by the quadriceps muscles at the knee, could produce significant anterior displacement of the tibia, which may play a role in anterior cruciate ligament injury.     

Isometric fascicle behaviour of the biceps femoris long head muscle during Nordic hamstring exercise variations

ObjectivesTo compare biceps femoris long head (BFlh) muscle tendon unit and fascicle function during Nordic hamstring exercise (NHE) variations with different hip range of motion.DesignCross-sectional.MethodsTwelve healthy volunteers (age: 24 ± 4 years; mass: 77 ± 6 kg; height: 177 ± 4 cm) performed two NHE variations: NHE with hips in neutral (fixed) position (conventional NHE); and NHE with hip flexion/extension. BFlh fascicle length behaviour was assessed using a dual transducer ultrasound configuration. BFlh and semitendinosus muscle electromyography, lower limb kinematics and knee flexion moment were also recorded. A biomechanical model was used to estimate BFlh muscle-tendon unit (MTU) length. Statistical Parametric Mapping was used to assess timing differences in outcome variables across the movement.ResultsIn both variations, during much of the exercise (~30–80% of movement phase), BFlh fascicles undergo little length change (isometric) while the MTU lengthens. Fascicles stretched considerably just in the last ~20% of the exercise, and changes in fascicle length (<2 cm stretch) were smaller in comparison to changes in MTU length (<4 cm stretch). Hip flexion resulted in the muscle tendon unit and fascicles operating at longer lengths until approximately 80% of the movement phase.ConclusionsThe decoupling between fascicle and MTU length seen during the NHE variations suggests that stretch of the elastic tissue of the MTU has an important role in absorbing energy during Nordic hamstring exercises. This may be important when considering adaptations to BFlh muscle and connective tissues that might occur from NHE training.     

Relationship between lower limb EMG activity and knee frontal plane projection angle during a single-legged drop jump

ObjectivesTo assess a relationship between lower limb muscle activity and the frontal plane knee kinematics during a single-legged drop jump.DesignCorrelation study;SettingFunctional Anatomy Laboratory.Participants35 healthy collegiate male athletes.Main outcome measuresMuscle activity (%MVIC) of gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius and lateral gastrocnemius; peak knee frontal plane projection angle; and Pearson's correlation coefficients between muscle activity and peak knee frontal plane projection angle. All outcomes were assessed for both dominant and non-dominant limbs.ResultsSignificant correlations (r = 0.46–0.60, P < 0.05) were found between the muscle activities of the gluteus maximus, gluteus medius, biceps femoris, and semitendinosus, when compared to the knee frontal plane projection angle.ConclusionGluteal muscles and hamstring muscles are associated with the peak knee frontal plane projection angle during a single-legged drop jump test. Thus, gluteal and hamstring muscle activities should be considered when developing rehabilitation or injury prevention programs.     

恢复期脑卒中患者膝关节最大等长收缩时大腿肌群表面肌电信号特征研究

目的:探讨脑卒中恢复期偏瘫患者膝屈伸最大等长收缩(maximum isometric voluntary contraction,MIVC)时部分大腿肌肉表面肌电(surfaceelectromyography,sEMG)信号特征,为恢复期脑卒中患者的康复治疗提供客观依据。方法:28例脑卒中患者和20例年龄、性别相匹配的正常对照者。在膝关节屈伸MIVC时记录股内侧肌(vastus medialis,VM)、股直肌(rectus femoris,RF)、股外侧肌(vastus lateralis,VL)和股二头肌(biceps femoris,BF)sEMG信号,计算相应的积分肌电值(integrated EMG,iEMG)、协同收缩率(co-contraction ratio,CR)。结果:伸膝时,患侧VM、RF及VL的iEMG值显著小于正常对照及健侧iEMG(P<0.05);健侧RF的iEMG显著小于正常对照iEMG(P<0.05);屈膝时,患侧BF、VL及RF的iEMG显著小于正常对照(P<0.05)。患侧伸膝CR显著大于健侧及正常对照(P<0.05),患侧屈膝CR大于健侧及正常对照,但无统计学意义(P>0.05)。结论:恢复期脑卒中偏瘫患者双下肢肌肉收缩功能下降,患侧大腿伸肌存在轻度痉挛,肌力训练可作为患者康复训练的重点内容之一。     

Phosphorus‐31 magnetic resonance spectroscopy of skeletal muscle in maternally inherited diabetes and deafness A3243G mitochondrial mutation carriers

Purpose

To investigate high‐energy phosphate metabolism in striated skeletal muscle of patients with Maternally Inherited Diabetes and Deafness (MIDD) syndrome.

Materials and Methods

In 11 patients with the MIDD mutation (six with diabetes mellitus [DM] and five non‐DM) and eight healthy subjects, phosphocreatine (PCr) and inorganic phosphate (Pi) in the vastus medialis muscle was measured immediately after exercise using ³¹P‐magnetic resonance spectroscopy (MRS). The half‐time of recovery (t1/2) of monoexponentially fitted (PCr+Pi)/PCr was calculated from spectra obtained every 4 seconds after cessation of exercise. A multiple linear regression model was used for statistical analysis.

Results

Patients with the MIDD mutation showed a significantly prolonged t1/2 (PCr+Pi)/PCr after exercise as compared to controls (13.6±3.0 vs. 8.7±1.3 sec, P = 0.01). No association between the presence of DM and t1/2 (PCr + Pi)/PCr was found (P = 0.382).

Conclusion

MIDD patients showed impaired mitochondrial oxidative phosphorylation in skeletal muscle shortly after exercise, irrespective of the presence of DM. J. Magn. Reson. Imaging 2009;29:127–131. © 2008 Wiley‐Liss, Inc.