Effect of high-intensity intermittent cycling sprints on neuromuscular activity

High-intensity intermittent sprints induce changes in metabolic and mechanical parameters. However, very few data are available about electrical manifestations of muscle fatigue following such sprints. In this study, quadriceps electromyographic (EMG) responses to repeated all-out exercise bouts of short duration were assessed from maximal voluntary isometric contractions (MVC) performed before and after sprints. Twelve men performed ten 6-s maximal cycling sprints, separated by 30-s rest. The MVC were performed pre-sprints ( pre), post-sprints ( post), and 5 min post-sprints ( post5). Values of root-mean-square (RMS) and median frequency (MF) of vastus lateralis (VL) and vastus medialis (VM) were recorded during each MVC. During sprints, PPO decreased significantly in sprints 8, 9, and 10, compared to sprint 1 (- 8 %, - 10 %, and - 11 %, respectively, p < 0.05). Significant decrements were found in MVC post (- 13 %, p < 0.05) and MVC post5 (- 10.5 %, p < 0.05) compared to MVC pre. The RMS value of VL muscle increased significantly after sprints (RMS pre vs. RMS post: + 15 %, p < 0.05). Values of MF decreased significantly in both VL and VM after sprints. In conclusion, our results indicate that the increase in quadriceps EMG amplitude following high-intensity intermittent short sprints was not sufficient to maintain the required force output. The concomitant decrease in frequency components would suggest a modification in the pattern of muscle fiber recruitment, and a decrease in conduction velocity of active fibers.     

Using surface electrodes for the evaluation of the rectus femoris, vastus medialis and vastus lateralis muscles in children with cerebral palsy

The purpose of this study was to determine if surface electrodes are adequate in the determination of the activity patterns of the rectus femoris, vastus medialis and vastus lateralis in children with cerebral palsy (CP). Ninety patients with a diagnosis of CP underwent electromyography (EMG) testing. Surface electrodes were placed on the rectus femoris (RF), hamstrings, vastus medialis (VM) and vastus lateralis (VL). Muscle isolation tests revealed no cross-talk of the RF muscle on the vastii electrodes in any subject indicating surface EMG is sufficient for testing RF, VM and VL function in children. Muscle activation patterns during gait showed that the RF and not the VM or VL was active in mid-swing in the majority of cases.     

Effect of knee joint angle on neuromuscular activation of the vastus intermedius muscle during isometric contraction

The purpose of this study was to compare the relationship between surface electromyography (EMG) and knee joint angle of the vastus intermedius muscle (VI) with the synergistic muscles in the quadriceps femoris (QF) muscle group. Fourteen healthy men performed maximal voluntary contractions during isometric knee extension at four knee joint angles from 90°, 115°, 140°, and 165° (180° being full extension). During the contractions, surface EMG was recorded at four muscle components of the QF muscle group: the VI, vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles. The root mean square of the surface EMG at each knee joint angle was calculated and normalized by that at a knee joint angle of 90° for individual muscles. The normalized RMS of the VI muscle was significantly lower than those of the VL and RF muscles at the knee joint angles of 115° and 165° and those of the VL, VM, and RF muscles at the knee joint angle of 140° (P<0.05). The present results suggest that the neuromuscular activation of the VI muscle is regulated in a manner different from the alteration of the knee joint angle compared with other muscle components of the QF muscle group.     

EMG threshold determination in eight lower limb muscles during cycling exercise: a pilot study

The first aim of this study was to verify the occurrence of the EMG threshold (EMG (Th)) in each of eight lower limb muscles (vastus lateralis [VL], vatus medialis [VM], rectus femoris [RF], semimembranosus [SM], biceps femoris [BF], gastrocnemius lateralis [GL] and medialis [GM], and tibialis anterior [TA]) during incremental cycling exercise. The second aim was to investigate the test-retest reproducibility of the EMG (Th) occurrence. Six sedentary male subjects (27 +/- 1 years) performed the same incremental cycling test until exhausted, (workload increments of 25 W/min starting at 100 W) twice. During the tests, the EMG Root Mean Square (RMS) response was studied in the aforementioned muscles. The EMG (Th) was detected mathematically from the RMS vs. workload relationship. All the subjects showed an EMG (Th) in the VL muscle, and the response was reliable in both tests (246 +/- 33 W and 254 +/- 33 W for the first and second test, respectively; coefficient of variation: 9.6 %, standard error of measurement: 28.9). However, few of them showed an EMG (Th) in the other muscles, especially in RF, SM or GM. When present, the EMG (Th) occurred at 75 - 80 % of the peak power output obtained during the tests. Our results suggest that EMG (Th) determination can be used as a reliable method for studying neuromuscular adjustments in the VL of untrained individuals, but not in other lower limb muscles.     

The effects of ice application over the vastus medialis on the activity of quadriceps femoris assessed by muscle function magnetic resonance imaging

AIM: The purpose of this study was to investigate the effect of ice application for the muscle vastus medialis (VM) on the activation pattern of the quadriceps femoris muscle during repetitive knee extensions using muscle function magnetic resonance imaging (mfMRI) technique. METHODS: Seven men underwent transverse relaxation time (T2)-weighted magnetic resonance imaging (spin echo, TR/TE=1500/25, 80 ms, 10 mm slice thickness and gap) of their right thigh at rest and immediately after isotonic knee extension exercise with 5 sets of 10 repetitions at a load equal to 70% of their 10 repetitions with and without skin cooling. Cooling over surface skin of the VM was carried out for 3 min before and during 60-s of each rest interval between the knee extension exercise. RESULTS: The relative change in T2 of the muscle vastus intermedius increased significantly more by skin cooling than the control (p<0.01), but not the muscle rectus femoris (RF), muscle vastus lateralis, and VM. CONCLUSION: These results suggest that selective skin cooling combined with repeated muscle contraction facilitates the activation of other synergistic muscles, making this technique useful for activating the agonist muscles expected for injured muscle in training and rehabilitation.     

Quadriceps EMG/force relationship in knee extension and leg press

PURPOSE: This study compared the relationship between surface electromyographic (EMG) activity and isometric force of m. quadriceps femoris (QF) in the single-joint knee extension (KE) and the multi-joint leg press (LP) exercises. METHODS: Nine healthy men performed unilateral actions at a knee angle of 90 degrees at 20, 40, 60, 80, and 100% of maximal voluntary contraction (MVC). EMG was measured from m. vastus lateralis (VL), m. vastus medialis (VM), m. rectus femoris (RF), and m. biceps femoris (BF). RESULTS: There were no differences in maximum EMG activity of individual muscles between KE and LP. The QF EMG/force relationship was nonlinear in each exercise modality. VL showed no deviation from linearity in neither exercise, whereas VM and RF did. BF activity increased linearly with increased loads. CONCLUSIONS: The EMG/force relationship of all quadricep muscles studied appears to be similar in isometric multi-joint LP and single-joint KE actions at a knee angle of 90 degrees. This would indicate the strategy of reciprocal force increment among muscles involved is comparable in the two models. Furthermore, these data suggest a nonuniform recruitment pattern among the three superficial QF muscles and surface EMG recordings from VL to be most reliable in predicting force output.     

Muscle deoxygenation and neural drive to the muscle during repeated sprint cycling

PURPOSE: To investigate muscle deoxygenation and neural drive-related changes during repeated cycling sprints in a fatiguing context. METHODS: Nine healthy male subjects performed a repeated-sprint test (consisting of 10 x 6-s maximal sprints interspaced by 30 s of recovery). Oxygen uptake was measured breath-by-breath; muscle deoxygenation of the vastus lateralis was assessed continuously using the near-infrared spectroscopy technique. Surface electromyograms (RMS) of both vastus lateralis and biceps femoris were also recorded. Furthermore, before and after the repeated-sprint test, the percentage of muscle activation by voluntary drive (twitch-interpolated method) was measured during a maximal voluntary contraction. RESULTS AND DISCUSSION: Consistent with previous research, our data showed a significant power decrement during repeated-sprint exercise. There was also a progressive muscle deoxygenation, but our data showed that the ability of the subjects to use available O2 throughout the entire repeated-sprint test was well preserved. Our data displayed a significant decrement in the RMS activity during the acceleration phase of each sprint across the repeated-sprint exercise. Moreover, decrement in motor drive was confirmed after exercise by a significant decrease in both percentage of voluntary activation and RMS/M-wave ratio during a maximal voluntary contraction. CONCLUSION: In this experimental design, our findings suggest that the ability to repeat short-duration (6 s) sprints was associated with the occurrence of both peripheral and central fatigue.     

Heterogeneous recruitment of quadriceps muscle portions and fibre types during moderate intensity knee-extensor exercise: effect of thigh occlusion

The involvement of quadriceps femoris muscle portions and fibre type recruitment was studied during submaximal knee-extensor exercise without and with thigh occlusion (OCC) and compared with responses during intense exercise. Six healthy male subjects performed 90-s of moderate exercise without (MOD; 29±4 W) and with thigh OCC, and moderate exercise followed by 90-s of intense exercise (HI; 65±8 W). Temperatures were continuously measured in m. vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) and successive muscle biopsies were obtained from VL. During MOD, muscle temperature increase (Δ T _m) in RF was 0.52±0.09 °C, which was 57% and 73% higher ( P <0.05) than in VL and VM, respectively. During OCC, Δ T _m in RF was 0.39±0.05 °C, which was not different from VM but 54% higher ( P <0.05) than in VL. After MOD, muscle CP in slow twitch (ST) and fast twitch (FT) fibres was 81% and 91% of resting levels, respectively, with lower ( P <0.05) values after OCC (15% and 22%) and HI (24% and 13%). After MOD, OCC and HI, a total of 48%, 93% and 96% of the ST fibres had CP levels below mean-1 SD, respectively, with corresponding values for FT fibres being 41%, 89% and 100%, respectively. In conclusion, a heterogeneous recruitment of the quadriceps muscle portions and muscle fibres was observed during submaximal knee-extensor exercise, whereas recruitment pattern was homogenous during intense exercise. Thigh OCC caused an altered recruitment of fibres and muscle portions, suggesting a significant afferent response affecting the activation of fibres in the contracting muscles.     

Muscle activation during lower body resistance training

This study evaluated the biceps femoris (BF), rectus femoris (RF), and vastus lateralis (VL) activation and activation ratios of a variety of resistance training exercises characterized by knee extension, and determined if subject strength or gender affects these variables. The exercises evaluated included the leg extension, squat, deadlift, lunge, and step up. Subjects included 20 athletes and recreationally active college students. Electromyography (EMG) of the muscles expressed as a percentage of maximum voluntary isometric contraction (MVIC), as well as the BF to RF and BF to VL EMG ratio, were determined for each exercise. There was no significant interaction between gender and exercise type for the RMS EMG of the BF (p = 0.67), RF (p = 0.53), or VL (p = 0.06). Main effects were found for the RMS EMG of the BF (p = 0.00), RF (p = 0.00), and VL (p = 0.00), as well as the RMS EMG of the BF to RF activation ratio (p = 0.00) and BF to VL activation ratios (p = 0.003), between exercises. Peak RMS EMG was also assessed. Post hoc analysis identified specific differences in muscle activation and ratios between exercises. Clinicians should consider the magnitude of muscle activation and activation ratios when prescribing hamstring and quadriceps exercises.     

Assessment of magnetic resonance techniques to measure muscle damage 24 h after eccentric exercise

The study examined which of a number of different magnetic resonance (MR) methods were sensitive to detecting muscle damage induced by eccentric exercise. Seventeen healthy, physically active participants, with muscle damage confirmed by non‐MR methods were tested 24 h after performing eccentric exercise. Techniques investigated whether damage could be detected within the quadriceps muscle as a whole, and individually within the rectus femoris, vastus lateralis (VL), vastus medialis (VM), and vastus intermedius (VI). Relative to baseline values, significant changes were seen in leg and muscle cross‐sectional areas and volumes and the resting inorganic phosphate concentration. Significant time effects over all muscles were also seen in the transverse relaxation time (T2) and apparent diffusion coefficient (ADC) values, with individually significant changes seen in the VL, VM, and VI for T2 and in the VI for ADC. A significant correlation was found between muscle volume and the average T2 change (r = 0.59) but not between T2 and ADC or Pi alterations. There were no significant time effects over all muscles for magnetization transfer contrast images, for baseline pH, phosphocreatine (PCr), phosphodiester, or ATP metabolite concentrations or the time constant describing the rate of PCr recovery following exercise.     

Effets d'une complémentation nutritionnelle en vitamines et minéraux sur la chute de force et les marqueurs biologiques consécutifs à un exercice excentrique chez des personnes âgées

Purpose

The effects of vitamins and minerals complex supplementation on maximal voluntary contraction decrease (FMV) and biological markers following an eccentric exercise at old people.

Method

Sixteen elderly subjects took either placebo (Pl group) or vitamins and minerals (Isoxan Senior, NHS, Rungis, France) (group S) for 21 d before an eccentric exercise and for 3 d after the exercise. The FMV and surface EMG activity (RMS) of the vastus lateralis (VL), vastus médialis (VM) and rectus fémoris (RF) were recorded before (Pre), immediately after (Post), 24 h (Post 24) and 48 h (Post 48) after the exercise. CCVThe creatine kinase (CK), lactate déshydrogénase, malondialdéhyde, and tumor necrosis Factor (TNFα) levels were analyzed.

Results

The reduced MVC (S: 11,2 ± 4,8%; Pl: 17,8 ± 10,4%, P < 0,01) after exercise was associated with a significant reduction in RMS VL, RMS VM and RMS RF values for both groups. A faster FMV recovery appeared at 48 h for the S group (P < 0.05). CK and TNFα values increased in post-exercise.

Conclusion

A dietary supplementation of a vitamin and mineral complex does not attenuate the loss of contractile function immediately after the running exercise, and it may accelerate the recovery of maximal force capacity after 48 h by limiting the post-exercise pro-inflammatory processes.     

The effects of a prolonged running exercise on strength characteristics

The aim of this study was to examine concentric, isometric, and eccentric strength reductions in the quadriceps muscle following a prolonged running exercise. Before and after a 2 h run (28.4+/-1.4 km) peak torque (PT) of the knee extensors at angular velocities of -120, -90, -60, 0, 60, 120, 180, 240 degrees x s(-1) using an isokinetic dynamometer, electromyographic (EMG) activity of the vastus lateralis (VL) and vastus medialis (VM) muscles and height of a counter movement jump were recorded in twelve well-trained triathletes. Counter movement jump performances decreased by 10% and PT values were all significantly lower (p < 0.01) at each angular velocity following the run. The torque loss was significantly (p < 0.01) greater under eccentric contractions (from 18 to 21%) than under concentric ones (from 11 to 14%). EMG activity (RMS) was lower in both VL and VM muscles after the 2 h run but no difference existed in RMS losses between concentric and eccentric contractions. The present results demonstrate that 1) a prolonged running exercise more greatly affects eccentric force production in the quadriceps muscle, and 2) this specificity seems to be due to an impairment of the muscular contractile mechanism rather than a modification to the neural input.     

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.     

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。     

The effects of rest interval and resistance training on quadriceps femoris muscle. Part II: EMG and perceived exertion

AIM: The purpose of this study was to examine the effects of rest interval on quadriceps femoris muscle activation and perceived exertion, during short-term resistance training. METHODS: Vastus medialis (VM) and vastus lateralis (VL) muscle electromyograms (EMG) were assessed in 15 males during a sustained 80% maximal voluntary contraction (MVC). During the pre-training evaluation, the absolute value of the 80% MVC (N.m) and contraction duration (s) was performed at 2, 4, and 6 weeks during the training period. Perceived exertion was measured via the Borg category-ratio scale every 5 s during the 80% MVC. Subjects were randomly assigned to 3 groups: group 1 received a 40 s rest interval in between exercise sets, group 2 received a rest period of 160 s, and the control group did not participate in training. Groups 1 and 2 performed isokinetic knee extensions at 180 deg.s(-1) 2 days per week for 6 weeks. RESULTS: The results demonstrated a significant decrease in VM EMG within the initial portion of the 80% MVC across the training period in the short rest interval group. The long rest interval and control groups showed no significant changes in VM EMG during 1st part of the contraction across the training period, whereas the control group exhibited a significant reduction in VL EMG across weeks 4 to 6. VL EMG increased during the 80% MVC in the control group across the training period. VM EMG increased during the sustained contractions in the long rest interval and control groups across the training period. The perceived exertion response was lower in the 1st part of the 80% MVC in the short and long rest interval groups, but not in the control group, across the training period. The results also showed a significant decrease in perceived exertion at the end of the sustained contraction in the short rest interval group, but not in the long rest interval group or the control group. CONCLUSIONS: The findings from this study suggest that the application of relatively short rest intervals in between sets of resistance exercise induced a greater neuromuscular response of the VM muscle during short-term training.     

Prior muscular exercise affects cycling pattern

The aim of this study was to investigate the effect of concentric or eccentric fatiguing exercise on cycling pattern. Eleven well trained cyclists completed three sessions of cycling (control cycling test [CTRL], cycling following concentric [CC] or eccentric [ECC] knee contractions) at a mean power of 276.8 +/- 26.6 Watts. Concentric and eccentric knee contractions were performed at a load corresponding to 80 % of one repetition maximum with both legs. Before and after CTRL, CC or ECC knee contractions and after cycling, a maximal voluntary contraction (MVC) test was performed. Cardiorespiratory, mechanical and electromyographic activity (EMG) of the rectus femoris, vastus lateralis and biceps femoris muscles were recorded during cycling. A significant decrease in MVC values was observed after CC and ECC exercises and after the cycling. ECC exercise induced a significant decrease in EMG root mean square during MVC and a decrease in pedal rate during cycling. EMG values of the three muscles were significantly higher during cycling exercise following CC exercise when compared to CTRL. The main finding of this study was that a prior ECC exercise induces a greater neuromuscular fatigue than a CC exercise, and changes in cycling pattern.     

Effects of lidocaine into knee on QF strength and EMG in patients with ACL lesion

PURPOSE: In our previous study, we found that injection of lidocaine into intact knees reduced the maximal voluntary contraction (MVC) and integrated electromyogram (I-EMG) of the quadriceps femoris (QF). This study was designed to investigate changes in the MVC and I-EMG of the QF in response to lidocaine, in patients with anterior cruciate ligament (ACL) lesion, to evaluate alpha-motoneuron activity innervating the QF. METHODS: The MVC of knee extension and I-EMG of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles were measured in eight patients with ruptured ACL, before and after lidocaine injection into the knee. RESULTS: There were no significant differences between preinjection and postinjection values of MVC (preinjection: 167 +/- 49 N.m; postinjection: 164 +/- 55 N.m) and I-EMG (preinjection: VL: 0.11 +/- 0.06, VM: 0.13 +/- 0.10, RF: 0.09 +/- 0.04) (postinjection: VL: 0.12 +/- 0.07, VM: 0.13 +/- 0.10, RF: 0.09 +/- 0.05). CONCLUSION: Our results indicated that hindrance of afferent feedback from the knee in patients with ACL rupture did not significantly change alpha-motoneuron activity. Lidocaine injection into the knee joint of the subjects in this study only attenuated afferent feedback from mechanoreceptors in the knee joint cavity, but not in the ACL, as afferent feedback from ACL was already lost due to ACL rupture. This indicated that attenuation of afferent feedback from mechanoreceptors in the knee joint cavity other than the ACL did not significantly decrease the activity of alpha-motoneurons innervating the QF during MVC exertion. Therefore, our findings provide evidence that afferent feedback from the ACL has a major influence on the MVC exertion of the QF.     

Possible mechanism of quadriceps femoris weakness in patients with ruptured anterior cruciate ligament

PURPOSE: The purpose of this study was to test the hypothesis that loss of afferent feedback due to rupture of anterior cruciate ligament (ACL) is the cause of quadriceps femoris (QF) weakness through gamma loop. Two experiments were designed to prove our hypothesis. METHODS: In experiment 1, the maximal voluntary contraction (MVC) of knee extension and integrated electromyogram (I-EMG) of vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) were measured in 13 patients with ruptured ACL and 7 healthy volunteers before and after injection of anesthetic agent into the knee. In experiment 2, MVC of knee extension and I-EMG of the VM, VL, and RF were measured in 13 patients with ruptured ACL, 7 knee-anesthetized healthy subjects, and 12 normal subjects, before and after 20-min vibration stimulation applied to the infrapatellar tendon. RESULTS: The results of experiment 1 revealed that injection of anesthetic agent into the knee capsule resulted in significant decrease of MVC and I-EMGs. In experiment 2, the mean percentage change of MVC in the control group was significantly lower than that in the other two groups. There was no significant difference between knee-anesthetized group and patients with ruptured ACL. The mean percentage change of I-EMG showed a pattern similar to that of MVC. CONCLUSION: Our results suggest that loss of feedback from mechanoreceptors in ACL is the underlying mechanism of weakness of QF in patients with ACL lesion. This conclusion is based on chronic suppression of recruitment of high-threshold motor units during voluntary contraction because ACL lesion leads to chronic reduction in Ia-feedback to muscles around the knee due to a lack of feedback from ACL to gamma motor neurons.     

Gender, muscle, and velocity comparisons of mechanomyographic and electromyographic responses during isokinetic muscle actions

The purpose of this study was to examine the responses of peak torque (PT), mean power output (MP), mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) in males and females during maximal, concentric isokinetic muscle actions. Subjects performed maximal leg extensions at 60 degrees s(-1), 120 degrees s(-1), 180 degrees s(-1), 240 degrees s(-1), 300 degrees s(-1), 360 degrees s(-1), 420 degrees s(-1), and 480 degrees s(-1). No gender differences were observed, but there were muscle-specific differences for the patterns of MMG MPF, EMG amplitude, and EMG MPF. The MP and MMG amplitude increased to 180-240 degrees s(-1), plateaued, and then decreased to 480 degrees s(-1). MMG MPF for the VL and VM remained unchanged to 300 degrees s(-1), but then increased to 480 degrees s(-1). The EMG amplitude for the RF and EMG MPF for the VL decreased across velocity. Overall, these findings indicated that there were muscle-specific, velocity-related differences in the associations among motor control strategies (EMG amplitude and MPF) and the mechanical aspects of isokinetic muscular activity (MMG amplitude and MPF).     

New insights into the function of the vastus medialis with clinical implications

PURPOSE: To investigate the gross anatomy of the distal portion of the quadriceps, and to compare the relative contributions of the vastus medialis oblique (VMO) and vastus lateralis (VL) during dynamic weight-bearing conditions. METHODS: Dissection was carried out on 10 cadavers by a longitudinal incision from the anterior superior iliac spine to the patella and completed with upper and lower transverse cuts to reinvestigate the gross anatomy and innervation patterns of the quadriceps femoris. A biomechanical test of knee kinematics was conducted on 10 healthy male volunteers. Maximal isometric force, squat jump, and drop movement jump exercises were performed on a force plate and filmed using a Saga-3 3D system, and surface EMG activity was recorded for the VMO and the VL. RESULTS: The oblique fibers of the vastus medialis (VM) are not only attached to the medial border of the patella, but they also have a small region of direct continuity with the patellar tendon. Furthermore, VMO fibers in the middle and proximal thirds of the thigh attached to vastus intermedius, whereas distally, the fibers were independent. Both parts of the VM (proximal and distal) had independent motor points. During jumping exercises, the VMO and VL were activated in a coordinated manner in a squat jump using both legs. However, in a single-leg squat jump (which challenged the stability of the knee joint more acutely), VMO activation was higher during landing. CONCLUSION: VMO activity was pronounced during the weight-bearing conditions, with increased medial and lateral knee movements. This suggests that the VM should not be considered simply as a knee extensor or as a muscle whose main role is to maintain normal patellar tracking.