Lateral Hamstrings Research Articles

Efficacy of Cold-Water Immersion in Treating Delayed Onset Muscle Soreness in Male Distance Runners

PURPOSE:Cold-water immersion (CWI) is a frequently used modality to treat Delayed-Onset Muscle-Soreness (DOMS); however its effectiveness in attenuating performance decrements remains unclear. Therefore we examined CWI effectiveness in reducing the negative effects of DOMS on single-leg triple hop performance (SLTH) in competitive distance runners. METHODS:Twelve male distance runners (Age: 19.25±1.14yrs, Height: 177.91±3.96cm, Weight: 65.44±4.77kg) participated in four consecutive days of testing. Baselines (D1) on single leg triple hops for total distance (SLTH, cm) and surface electromyography muscle activation (sEMG, mV) on the lateral gastrocnemius (LG), medial and lateral hamstrings (MH, LH) and lateral quadriceps (LQ) were established on Day 1. Bilateral DOMS was then induced with a drop jump protocol. Next, subjects randomly received CWI therapy (13°C for 20 minutes) on one leg (Tr) with the contralateral leg being the control (Cr). On Days 2, 3, and 4 subjects repeated SLTH and sEMG on each leg and received CWI on the same leg (Tr). Separate 2×4 repeated measures ANOVAs examined SLTH and sEMG differences across interventions and days with separate one-way repeated measures ANOVAs examining sEMG differences across days (p≤0.05). RESULTS: SLTH distances improved slightly between D1 and D4 (233.06±24.96, 244.55±21.17) (P=.028) in Cr after DOMS was induced. In Tr SLTH distances increased significantly between D1 and D4 (226.39±21.07, 255.18±24.92) (P=0.004). Comparisons between Cr and Tr over 4 days found significant differences at D3 (P=.037) and D4 (P=.042). In Tr, muscle activation amplitudes were significantly different across the days in all muscles (LG: p<.001, MH: p<.001, LH: p<.001, LQ: p<.001), with the amplitudes consistently lower than baseline on D2 but recovering to baseline by D3 in all muscles. However, in Cr activation amplitudes were not different in the muscle except in the LQ (p<.001) where amplitudes on D3 were lower than on D1 and D4. CONCLUSIONS: Using CWI appeared to successfully help recovery as seen on the SLTH and muscle activation amplitudes. Therefore, CWI is a positive treatment modality to improve subsequent performances following DOMS.

PNF의 Sprinter Pattern을 통한 하지의 근 활성도가 균형능력에 미치는 영향

In this study, for examining an effect of lower limbs` muscle activity on balance capability when applying sprinter pattern among the PNF, the experiment was conducted as followed. Under the object of 24 people diagnosed by hemiplegia, they were divided into control group and experimental group and the experiment was conducted on the experimental group, three times per a week for six weeks. Experimental group received Sprinter pattern of combined PNF upper extremity and lower extremity pattern. For the lower limbs` muscle activity, effective values of Vastus medialis laterails, medial lateral hamstrings, lateral gastrocnemius` action potential were analyzed. The balance ability tests was conducted with FICSIT-4, FSST and MTD-Balance system. For the significance test of control group and experimental group for measuring time by exercise application method, two-way repeated measure ANOVA was conducted and for the significance test among the groups by each measuring time, independent t-test was conducted. Also, for examining the correlation among the measuring item, pearson correlation was used for the analysis. As the result, the application of sprinter pattern increased muscle activity of lower limbs in paretic side and improve static and dynamic balance ability effectively. Therefore, it will be necessary to develop new intervention by combining active application of the therapeutic intervention program for lower limbs` effective muscle mobilizing in paretic side with various exercising patterns.

Hamstring Musculotendon Dynamics during Stance and Swing Phases of High-Speed Running

Hamstring strain injuries are common in sports that involve high-speed running. It remains uncertain whether the hamstrings are susceptible to injury during late swing phase, when the hamstrings are active and lengthening, or during stance, when contact loads are present. In this study, we used forward dynamic simulations to compare hamstring musculotendon stretch, loading, and work done during stance and swing phases of high-speed running. Whole-body kinematics, EMG activities, and ground reactions were collected as 12 subjects ran on an instrumented treadmill at speeds ranging from 80% to 100% of maximum (avg max speed = 7.8 m·s(-1)). Subject-specific simulations were then created using a whole-body musculoskeletal model that included 52 Hill-type musculotendon units acting about the hip and the knee. A computed muscle control algorithm was used to determine muscle excitation patterns that drove the limb to track measured hip and knee sagittal plane kinematics, with measured ground reactions applied to the limb. The hamstrings lengthened under load from 50% to 90% of the gait cycle (swing) and then shortened under load from late swing through stance. Although peak hamstring stretch was invariant with speed, lateral hamstring (biceps femoris) loading increased significantly with speed and was greater during swing than stance at the fastest speed. The biarticular hamstrings performed negative work on the system only during swing phase, with the amount of negative work increased significantly with speed. We concluded that the large inertial loads during high-speed running appear to make the hamstrings most susceptible to injury during swing phase. This information is relevant for scientifically establishing muscle injury prevention and rehabilitation programs.

Tibial Tuberosity Osteotomy for Patellofemoral Realignment Alters Tibiofemoral Kinematics

Background: Tibial tuberosity realignment surgery is performed to improve patellofemoral alignment, but it could also alter tibiofemoral kinematics. Hypothesis: After tuberosity realignment in the malaligned knee, the reoriented patellar tendon will pull the tuberosity back toward the preoperative position, thereby altering tibiofemoral kinematics. Study Design: Controlled laboratory study. Methods: Ten knees were tested at 40°, 60°, and 80° of flexion in vitro. The knees were loaded with a quadriceps force of 586 N, with 200 N divided between the medial and lateral hamstrings. The position of the tuberosity was varied to represent lateral malalignment, with the tuberosity 5 mm lateral to the normal position; tuberosity medialization, with the tuberosity 5 mm medial to the normal position; and tuberosity anteromedialization, with the tuberosity 10 mm anterior to the medial position. Tibiofemoral kinematics were measured using magnetic sensors secured to the femur and tibia. A repeated measures analysis of variance with a post hoc Student-Newman-Keuls test was used to identify significant (P < .05) differences in the kinematic data between the tuberosity positions at each flexion angle. Results: Medializing the tibial tuberosity primarily rotated the tibia externally compared with the lateral malalignment condition. The largest average increase in external rotation was 13° at 40° of flexion, with the increase significant at each flexion angle. The varus orientation also increased significantly by an average of 1.5° at 40° and 80°. The tibia shifted significantly posteriorly at 40° and 60° by an average of 4 mm and 2 mm, respectively. Shifting the tuberosity from the medial to the anteromedial position translated the tibia significantly posteriorly by an average of 2 mm at 40°. Conclusion: After tibial tuberosity realignment in the malaligned knee, the altered orientation of the patellar tendon alters tibiofemoral kinematics. Clinical Relevance: The kinematic changes reduce the correction applied to the orientation of the patellar tendon and could alter the pressure applied to tibiofemoral cartilage.

Effects of Bridging Exercise Methods on the Muscular Activity of the Neck, Trunk and Lower Limbs

[Purpose] The purpose of this study was to investigate the effects of different bridging exercise methods, varied by the position of the lower limbs, on the muscular activity of the neck, trunk, thigh and lower limbs. [Subjects] The subjects of this study were 14 males in their twenties. [Methods] The muscular activities of the longissimus capitis and sternocleidomastoid in the neck, the erector spinae and rectus abdominis in the trunk, the rectus femoris and lateral hamstring in the thigh, and the tibialis anterior and lateral head of the gastrocnemius in the lower leg were measured using a surface electromyography. [Results] The comparison of the muscular activities showed significant differences in the longissimus capitis, rectus abdominis, erector spinae, rectus femoris, biceps femoris and gastrocnemius muscles among the bridging exercise methods. [Conclusion] Action and activity of muscle groups varies according to the position of the lower limbs during the bridging exercise.

Neuromuscular alterations exist with knee osteoarthritis presence and severity despite walking velocity similarities

Background Neuromuscular strategies during walking in individuals with knee osteoarthritis are being explored for diagnostic information; however, isolating differences to disease progression is difficult given walking velocity decreases with osteoarthritis severity. This study investigated lower extremity electromyograms during walking in asymptomatic individuals and individuals with different severities of knee osteoarthritis who walked with similar self-selected velocities. Methods Muscle activity in lateral and medial gastrocnemius, vastus lateralis and medialis, rectus femoris and the lateral and medial hamstrings was monitored during self-selected walking in 230 subjects with asymptomatic knees, moderate and severe knee osteoarthritis. Sixteen asymptomatic individuals, 16 individuals with moderate and 15 individuals with severe knee osteoarthritis were identified based on similarities in average walking velocity. Principal component analysis was employed to derive amplitude and temporal characteristics of the electromyographic (EMG) waveforms. Analysis of variance models tested for group and muscle differences in principal pattern scores (α = 0.05). Bonferroni post hoc testing was utilized on all significant findings. Findings Despite similar walking velocities, individuals with moderate knee OA had elevated and prolonged quadriceps and elevated lateral hamstring activity compared to asymptomatic individuals (P < 0.05). A diminished phase shift between medial and lateral gastrocnemius muscle activation, greater and prolonged lateral compared to medial hamstring activation were found in the severe group compared to asymptomatic and moderate knee OA groups (P < 0.05). Interpretation Lower extremity neuromuscular function during walking is altered with the presence and severity of knee osteoarthritis and not simply a direct function of walking velocity.

Lower Body Stiffness and Muscle Activity Differences Between Female Dancers and Basketball Players During Drop Jumps

Background:Anterior cruciate ligament (ACL) injuries often occur during landing, with female athletes at higher injury risk than male athletes. Interestingly, female dancers have lower ACL injury rates than do female athletes in general.Hypothesis:Female dancers will have earlier and greater lower extremity muscle activity and higher sagittal knee joint and leg stiffness than will female basketball players.Study Design:Cross-sectional group comparison.Methods:Fifty-five healthy female athletes (35 dancers, 20 basketball players) performed 5 double-leg drop jumps from a 45-cm box. Surface electromyography (onsets and amplitudes; prelanding and postlanding) was recorded from the lateral gastrocnemius, medial and lateral hamstrings, lateral quadriceps muscles with a 3-dimensional electromagnetic tracking system, and forceplates recording biomechanics (leg spring stiffness and knee joint stiffness).Results:Compared with basketball players, dancers had greater leg spring stiffness (P = 0.047) but similar knee joint stiffness (P = 0.44). Although no significant differences were observed in overall muscle onset times (P = 0.22) or activation amplitudes (prelanding, P = 0.60; postlanding, P = 0.78), small to moderate effect sizes (ESs) suggest trends in dancers toward earlier (ES = 0.53) and higher medial hamstrings activation pre- (ES = 0.55) and post- (ES = 0.41) landing and lower lateral quadriceps (ES = 0.30) and higher gastrocnemius (ES = 0.33) postlanding muscle activation.Conclusions:In dancers, the higher leg spring stiffness and trends toward higher hamstrings prelanding and postlanding, as well as lower quadriceps and higher gastrocnemius activation postlanding with similar knee joint stiffness, indicate lower extremity neuromechanical differences across other joints.Clinical Relevance:Female dancers may have lower extremity neuromechanics that are different from those of basketball players during drop jumps. If dancers use ACL-protective strategies during activity, then their training routines should be further investigated to improve ACL injury prevention programs.

The role of neural tension in hamstring flexibility

Resistance to stretch, electromyographic (EMG) response to stretch, stretch discomfort and maximum range of motion (ROM) were measured during passive hamstring stretches performed in the slump test position (neural tension stretch) and in the upright position (neutral stretch) in eight healthy subjects. Stretches were performed on an isokinetic dynamometer at 5°/s with the test thigh flexed 40° above the horizontal, and the seat back at 90° to the horizontal. Surface EMG signals were recorded from the medial and lateral hamstrings during stretches. Knees were passively extended to maximum stretch tolerance with test order (neural tension vs neutral) alternated between legs. For neural tension stretches, the cervical and thoracic spine were manually flexed. Maximum ROM was 8° less for the neural tension stretch vs the neutral stretch (P<0.01). Resistance to stretch was 14-15% higher for the neural tension stretch vs the neutral stretch (P<0.001) at common joint angles in the final third of ROM. Stretch discomfort and EMG response were unaffected by neural tension. In conclusion, an increased passive resistance to stretch with the addition of neural tension during passive hamstring stretch despite no change in the EMG response indicates that passive extensibility of neural tissues can limit hamstring flexibility.

An electromyographic exploratory study comparing the difference in the onset of hamstring and quadriceps contraction in patients with anterior knee pain

Idiopathic anterior knee pain in teenagers and young adults is a common condition. Patellar maltracking has been considered as a causative factor. The aim of our study was to investigate whether there was a difference in the timing of electromyographic (EMG) activity in the medial and lateral hamstring and quadriceps muscles of patients with anterior knee pain compared to asymptomatic control participants. This was a cross sectional observational study measuring EMG activation patterns. Two groups of participants were tested, one patient (mean age 15 years, n = 20) and one asymptomatic control (mean age 16 years, n = 17). Surface EMG (sampling rate 1000 Hz) was recorded from vastus medialis obliqus, vastus lateralis, and the medial and lateral hamstrings during three repetitions of maximal voluntary isometric contractions. The relative timing of the medial and lateral quadriceps and hamstrings was evaluated. The mean (95% confidence interval) difference between the groups in the lateral–medial hamstring onset timing was 53.8 (1.9 to 105.6) ms during the maximal contraction. An independent t test showed that this difference was statistically significant (p = 0.043). The differences between the groups in the relative VMO to VL onset did not reach statistical significance. The results of this study suggest that the lateral hamstrings contract significantly earlier in patients with AKP compared to healthy controls for this small cohort. This altered activation pattern could produce external rotation of the tibia on the femur and cause lateral patella tracking.

Changing filtering parameters affects lower extremity pre-landing muscle activation onset times

Surface electromyography(sEMG) is extensively used to examine muscle activation. Although raw sEMG signals are often filtered using Root-Mean-Square(RMS) algorithms, little agreement exists as to the time window over which signals should be processed. We examined the effects of differing RMS filtering windows on muscle onset times. Fifty-five participants performed 5 drop jumps from a 45 cm box and lateral gastrocnemius(LG), medial and lateral hamstring(MH, LH) and lateral quadriceps(LQ) muscle activity were acquired. Signals were collected at 1000 Hz and RMS filtered using 3 ms, 10 ms, 20 ms and 25 ms windows. Muscle onset times differed by RMS windows for the LG(p= 0.01), MH(p= 0.002), and LH(p= 0.000), but not for the LQ(p=0.14). Pairwise comparisons indicated that LG onsets were earlier with the 3 ms vs. 20 ms window, MH onsets were earlier with the 3 ms vs. 20 ms and 25 ms windows, and LH onsets were earlier with the 3 ms, 10 ms, and 20 ms windows than the 25 ms window. Gastrocnemius and hamstring muscle onset times were substantially earlier when filtering raw sEMG data with 3 ms versus wider RMS windows(> 20 ms) during landing. Changing filtering parameters affects data interpretation when analyzing sEMG data using differing window widths. Additional research should determine optimal RMS window widths that maximize signal fidelity but still retain meaningful time differences.

Muscle Activation of the Uninjured Leg During an Acute Achilles Tendon Rupture

The purpose of this study was to describe muscle activation of the uninjured leg during an acute Achilles tendon rupture. Electromyographic (EMG) data were collected on the following muscles: medial hamstring, biceps femoris, gluteus medius, gluteus maximus, and the gastrocnemius while the participant was performing a round-off dismount type of maneuver in which she sustained an Achilles tendon rupture. Electromyographic data analysis suggested that the participant fell into a knee valgus flexed hip position on the uninjured leg immediately after the injury. Vastus medialis obliqueous activity indicated a position of knee valgus, whereas the shutdown of the gluteus medius and gluteus maximus indicated the patient's hip was falling into hip collapse. The lateral hamstring activity indicated an attempt to catch the falling pelvis and that the medial hamstrings were most likely caught in the reflex arc of the gluteals. If the decreased EMG activity in the uninjured limb occurred subsequently to the rupture, the resultant kinetic chain activity displays the way the body adapts because of a traumatic injury of the lower extremity. Reproduction of the muscular pattern of activity in landing maneuvers and subsequent training intervention may reveal targeting muscle groups that have been shown to fail early. Targeting the muscle groups through training interventions may have an impact on injury reduction patterns.

Normative EMG activation patterns of school-age children during gait

Gait analysis is widely used in clinics to study walking abnormalities for surgery planning, definition of rehabilitation protocols, and objective evaluation of clinical outcomes. Surface electromyography allows the study of muscle activity non-invasively and the evaluation of the timing of muscle activation during movement. The aim of this study was to present a normative dataset of muscle activation patterns obtained from a large number of strides in a population of 100 healthy children aged 6–11 years. The activity of Tibialis Anterior, Lateral head of Gastrocnemius, Vastus Medialis, Rectus Femoris and Lateral Hamstrings on both lower limbs was analyzed during a 2.5-min walk at free speed. More than 120 consecutive strides were analyzed for each child, resulting in approximately 28,000 strides. Onset and offset instants were reported for each observed muscle. The analysis of a high number of strides for each participant allowed us to obtain the most recurrent patterns of activation during gait, demonstrating that a subject uses a specific muscle with different activation modalities even in the same walk. The knowledge of the various activation patterns and of their statistics will be of help in clinical gait analysis and will serve as reference in the design of future gait studies.

Lower Extremity Muscle Activation Changes Following a Standard 6-week Neuromuscular Training Program

Sex-dimorphic neuromuscular control patterns evident during landings are proposed to increase female anterior cruciate ligament (ACL) injury risk compared to males. Training programs aimed at modifying these high-risk patterns have been demonstrated to be an effective intervention for reducing ACL injury rates. It is unclear, however, how such programs lead explicitly to fewer ACL injuries. We propose that females adopt control strategies following training that more effectively counter potentially hazardous impact-induced external loads. PURPOSE: To examine the effects of a 6-week neuromuscular training program (NTP) on lower extremity muscle activation during a single-leg land and cut task. METHODS: Twenty three (12 trained, 11 control) recreational female athletes had lower extremity muscle electromyography (EMG) data quantified during 10 single-leg land-and-cut trials before (Base), immediately (Post 0), and six weeks (Post 6) after a six-week NTP. Surface EMG electrodes were secured over the muscle bellies of the medial (MH) and lateral hamstrings (LH), vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), and medial (MG) and lateral gastrocnemius (LG) of the dominant limb. The average RMS amplitudes were calculated for each muscle during two jump landing phases; 100 ms prior to ground contact (Pre) and ground contact to 50% of stance (Re). Pre and Re co-contraction indices were also quantified for thigh muscle pairs (VL-LH and VM-MH). Subject based means of the dependent variables were submitted to two-way repeated measures (time) ANOVAs to test for the main and interaction effects of time and group. RESULTS: Subjects demonstrated significantly (p < 0.05) greater Pre and Re LH and MH muscle activation, Re LG muscle activation, and Pre and Re VL-LH and VM-MH co-contraction at both Post 0 and Post 6 time points. Increases in Pre VM (p = 0.014) and Re MG (p = 0.006) activation were only noted at the Post 6 follow-up. CONCLUSION: Lower extremity muscle activation increased during dynamic single-leg landings following a 6-week NTP. Specifically, females increased hamstring and gastrocnemius activation magnitudes, and relative activation of the hamstrings to quadriceps, which may reduce ACL injury risk. Importantly, these beneficial adaptations may even be retained six weeks following training.

Neuromuscular Timing during Drop Jumps Between Healthy Women And Women With Semitendinosus-gracilis ACL Reconstruction

Anterior Cruciate Ligament (ACL) reconstruction with hamstring-gracilis (SG) autograft is one of the preferred surgical options in women advocating the return of knee stability. These women have shown neuromuscular compensatory strategies to maintain knee stability during landing tasks. PURPOSE: To identify neuromuscular timing imbalances of the quadriceps and hamstrings muscle groups during landing from a bilateral and single-legged drop jumps between women 1-5 years post SG ACL reconstruction and non-injured women. METHODS: Twenty-nine young women (non-injured = 15, SG = 14) performed five trials of a double-legged and single-legged drop jumps from a 60-cm and 40-cm height box, respectively. Participants had five bipolar Ag pre-amplified surface electromyography (EMG) electrodes attached on the skin over the vastus medialis, vastus lateralis, rectus femoris, medial and lateral hamstrings on the dominant leg for the non-injured women and in the reconstructed leg for women with ACL surgery. EMG data was collected at 1kHz. Data from all the quadriceps and hamstring muscles were averaged to represent each muscle group in its entirety. The time taken in seconds to reach peak EMG activity (latency) during the ground contact phase after landing was the variable of interest. Data was screened for normality and outliers previous to analyses. After data screening, independent t-tests were used to compare latency of the quadriceps and hamstrings between groups for both tasks. RESULTS: Twenty-seven participants were included for the double drop jump comparisons; a total of 26 participants were included in single-leg drop jump comparisons. No statistically significant differences during the double drop jump for latency of the quadriceps (control:.1709 ±.11805, SG:.1498 ±.17775; p = 0.734) and hamstrings (control:.2233 ±.13017, SG:.1990 ±.21555; p = 0.744) were found. Neither quadriceps (control:.3204 ±.16475, SG:.2175 ±.14024; p = 0.098) or hamstrings (control:.3692 ±.21629, SG:.2373 ±.16549; p = 0.091) latency comparisons reached statistical significance during the single leg drop jump. CONCLUSIONS: It appears that women with SG ACL reconstruction possess similar neuromuscular timing patterns for the quadriceps and hamstrings than women without knee surgery during double and single legged landings.

The Effects of Imagery on Performance and Pain Perception Associated with Delayed-Onset Muscle Soreness

Research has indicated that the use of imagery may aid in recovery from injuries and reduce the perception of pain in athletes during and after competitions. There is little research concerning acute pain and soreness, such as delayed-onset muscle soreness (DOMS). PURPOSE: To determine whether the use of guided imagery for healing will affect soreness, pressure pain threshold (PPT), and performance associated with DOMS. It was hypothesized that those who listen to a healing imagery script would report less soreness, higher pain threshold, and better performance following DOMS than a control group. METHODS: Participants (38) completed two days of testing with 48 hours between them. At the end of the first day, DOMS was induced by performing 6 sets of 15 reps of isokinetic eccentric exercise at -1.05 rad/sec. Each day consisted of tests of soreness, PPT, vertical jump, isokinetics at 6 speeds, and a Wingate test. 20 participants listened to a healing imagery script 10 times within the 48 hours after inducement of DOMS while 18 listened to relaxing music. RESULTS: Perception of muscle soreness was worse for the front and back of the leg (p<.01) regardless of group and the control group reported greater pain perception both before and after the intervention than the imagery group (p<.05). PPT was lower after treatment in the lateral hamstring regardless of group (p<.05). Peak torque for knee extension at 1.05 rad/sec was reduced after treatment for both groups (p<.01). Peak torque for knee flexion at 2.09, 3.14, 5.24, & 6.28 rad/sec was better after treatment for both groups (p<.05) and peak torque for flexion was better at 6.28 rad/sec (p<.05) for both groups. While the Power Drop percentage on the Wingate test appeared better for the imagery group and worse for the control group following treatment, this failed to reach statistical significance (p=.07). CONCLUSION: Healing imagery had no significant impact on perception of soreness, PPT, isokinetic measures, or anaerobic power testing. Based on the actual, but non-significant, changes in power drop results from the Wingate test, it appears that imagery could impact longer duration anaerobic performance as opposed to short duration performance. Further research is needed to determine if healing imagery can improve performance on longer anaerobic and possibly aerobic activities.

Knee Injury - Football

HISTORY: A 21 year old collegiate punter presents with persistent left knee pain after hyperextending it one week prior. The patient originally had complained of pain medially and over the lateral hamstring tendon which had improved with conservative treatment. On the day prior to presentation, he had increased pain after punting. He now complains of pain lateral to the patella and again over the lateral hamstring tendon. He reports pain only with punting, but not on kickoff. He denies any locking, clicking or weakness. He does report being unable to flex his knee fully. PHYSICAL EXAMINATION: Examination in the athletic training room revealed a 2+ left knee effusion. There is decreased knee flexion due to effusion, but full extension. The patient is able to squat and ambulate normally. There is no joint line tenderness, a negative McMurray's, negative patellar grind test. Lachmans, anterior drawer and varus/valgus stress are negative for laxity. There is tenderness laterally over the biceps femoris tendon. No palpable defects along muscle. There is no fibular head pain. He is neurovascularly intact distally. He has increased pain with resisted knee flexion. Knee aspiration was performed under sterile technique to alleviate discomfort from the effusion. The knee aspirate contained 20 ml of bloody fluid. DIFFERENTIAL DIAGNOSIS: Cruciate ligament injury Collateral ligament injury Meniscal injury Intra-articular fracture Chondral fracture Patellar dislocation Tear in deep portion of joint capsule TESTS AND RESULTS: Knee x-ray: Suprapatellar joint effusion MRI Left Knee: Fluid signal within the proximal popliteus muscle representing a small intramuscular tear at the myotendinous junction. Mild strain of semimembranosus muscle. FINAL/WORKING DIAGNOSIS: Popliteal strain/incomplete tear TREATMENT AND OUTCOMES: Compression, Ice and NSAID therapy Monitor knee effusion Activity as tolerated

The neuromuscular demands of altering foot progression angle during gait in asymptomatic individuals and those with knee osteoarthritis

To determine the immediate effects of a toe-out foot progression angle modification during gait on the major lower limb muscle activation characteristics and to establish whether asymptomatic individuals and those with moderate knee OA have similar responses. Seventeen patients with knee OA and 20 asymptomatic control subjects participated. Informed consent was obtained. Electromyographic (EMG) recordings were acquired from the lateral and medial gastrocnemii, vastus lateralis, vastus medialis, rectus femoris and the lateral and medial hamstrings during neutral and toe-out walking conditions. The EMG waveforms were amplitude normalized to maximal voluntary isometric contractions and time normalized to the gait cycle. Principal component analysis extracted principal waveform features. Analysis of variance models tested for main effects and interactions. Bonferroni post hoc testing was employed (alpha=0.05). Both groups altered foot progression angle by approximately 15 degrees during toe-out walking (P<0.05). A shift in gastrocnemius activation towards later stance (P<0.05) and increased magnitude and duration of quadriceps activation (P<0.05) was found. A differential activation occurred in the overall magnitude and principal shape of the lateral and medial hamstring musculature in the asymptomatic group only (P<0.05). Significant group differences were shown in each muscle analysis (P<0.05). Neuromuscular demands of adopting a toe-out gait differ from a neutral foot progression angle. Demands also differ between asymptomatic controls and patients with moderate knee OA. These findings have relevance for altered joint loading and changes in metabolic cost of this gait modification in individuals with knee OA.

Gender-Based Analysis of Hamstring and Quadriceps Muscle Activation During Jump Landings and Cutting

This study evaluated gender differences in the magnitude and timing of hamstring and quadriceps activation during activities that are believed to cause anterior cruciate ligament (ACL) injuries. Twelve men (age = 21.0 +/- 1.2 years; body mass = 81.61 +/- 13.3 kg; and jump height = 57.61 +/- 10.15 cm) and 12 women (age = 19.91 +/- 0.9 years; body mass = 64.36 +/- 6.14 kg; and jump height = 43.28 +/- 7.5) performed 3 repetitions each of the drop jump (jump) normalized to the subject's vertical jump height, and a sprint and cut at a 45-degree angle (cut). Electromyography (EMG) was used to quantify rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), lateral hamstring (LH), and medial hamstrings (MH) activation, timing, activation ratios, and timing ratios before and after foot contact for the jump and cut and normalized to each subject's hamstring and quadriceps maximum voluntary isometric contraction. Data were analyzed using an analysis of variance with results demonstrating that during the postcontact phase of the cut, men demonstrated greater LH and MH activation than women. In the precontact phase of the jump, men showed earlier activation of the VL and VM, than women. Women produced longer RF and VM muscle bursts during the postcontact phase of the cut. Additionally, men showed a trend toward higher hamstring to quadriceps activation ratio than women for the postcontact phase of the cut. This study provides evidence that men are LH dominant during the postcontact phase of the cut compared with women, whereas women sustain RF activation longer than men during this phase. Men activate quadriceps muscles earlier than women in the precontact phase of the jump. Training interventions may offer the potential for increasing the rate and magnitude of hamstring muscle activation. These outcomes should be evaluated using EMG during movements that are similar to those that cause ACL injuries to determine if gender differences in muscle activation can be reduced.

Hamstring To Quadriceps Timing And Activation Ratios Of High School Athletes During Cutting And Jumping

This study assessed hamstring and quadriceps timing and hamstring to quadriceps activation ratios (H:Q), and gender differences therein, during jump landings and cutting maneuvers. Subjects included 6 boys (age = 17.1 ± 0.9 years) and 6 girls (age = 15.7 ± 1.2 years). All subjects provided informed and parental consent and the study was approved by the university review board. Subjects performed 2 repetitions each of the drop jump from a height equal to their maximum vertical jump (J) as well as a sprint and cut at a 45 degree angle (C). Electromyographic (EMG) data were collected for the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), lateral hamstring (LH), and medial hamstring (MH). Root mean square (RMS) signal processing was used on all EMG data which were analyzed to assess the magnitude and timing of the muscles bursts pre and post landing for the J and C, using the average of 2 trials and normalized to maximal voluntary isometric contraction. The H:Q were calculated from the collective average of the hamstring muscles divided by the collective average of the quadriceps muscles. The timing of the foot contact was synchronized with the EMG system using a switch mat. Data were evaluated using an independent samples t-test to assess differences in muscle timing and H:Q for the pre and post foot contact for the J and C, for all muscles assessed. Significant gender differences were found for the timing of the MH activation (p ≤ 0.05) pre and post contact during the J, with boys demonstrating 24.4% earlier MH activation and a 19.8% longer burst after foot contact. Compared to boys, girls demonstrated 17.2% earlier MH activation during the C (p ≤ 0.05). Significant gender differences were also found in the H:Q activation ratios with boys demonstrating a 56.3% higher H:Q ratio after J landing (p ≤ 0.05). No other significant gender differences in the timing of muscle activation or the H:Q ratios were found. Counter-movement jump height was assessed as a measure of gender difference in training status. Girls demonstrated 73.7% of the jumping ability of the boys. This study confirms the existence of gender differences in the timing and magnitude of activation of MH during movements that are similar to those that cause ACL injuries. Strength and conditioning professionals are encouraged to prescribe hamstring training to their female athletes in an attempt to remediate gender differences in hamstring activation during J landings.

Do High Hamstring To Quadriceps Activation Ratios Impair Jumping Performance?

Recent reports suggest that training to increase the amount of hamstring activation and hamstring to quadriceps activation ratios (H:Q) may stabilize the knee during jump landings and cutting, and potentially prevent anterior cruciate ligament injuries. However, the potential effect of increased antagonist activation may impair the agonist, including the performance of activities involving knee extension. This study evaluated the relationship between H:Q and countermovement jump (CMJ) height. Subjects included 43 female high school and college students (age = 19.14 ± 1.8 years). All subjects provided informed consent, as well as parental consent for those who were less than 18 years old. The study was approved by the university review board. Subjects performed 2 repetitions of maximum voluntary isometric contractions (MVIC) for the quadriceps and hamstring muscles. Subjects also performed 2 repetitions each of the drop jump from a height equal to their countermovement jump (DJ). Electromyographic (EMG) data were collected for the rectus femoris, vastus lateralis, vastus medialis, lateral hamstring, and medial hamstring. Root mean square (RMS) signal processing was used on all EMG data which were analyzed to assess the magnitude and timing of the muscles' bursts pre and post landing for the DJ using the average of both trials and normalized to MVIC. The timing of the foot contact was synchronized with the EMG data using a switch mat. The H:Q were calculated from the collective average of the hamstring muscles divided by the collective average of the quadriceps muscles. Data were evaluated using a Pearson's correlation coefficient in order to examine the relationship between the subject's H:Q and CMJ height for both the pre and post foot contact phase of the DJ. Results revealed that pre landing H:Q was positively correlated to CMJ height (r = .35, p = 0.02). Post-landing H:Q was not correlated to CMJ height (r = .21, p = 0.18) This study demonstrates that high levels of hamstring activation, relative to the quadriceps, do not impair, and may be positively associated with CMJ performance. The prescription of additional hamstring training for female athletes appears unlikely to impair performance of exercises that involve dynamic knee and hip extension, such as the countermovement jump.