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PubMed1997

EMG analysis of lower extremity muscle recruitment patterns during an unloaded squat.

During an unloaded squat, hamstring and quadriceps co-contraction has been documented and explained via a co-contraction hypothesis. This hypothesis suggests that the hamstrings provide a stabilizing force at the knee by producing a posteriorly-directed force on the tibia to counteract the anterior tibial force imparted by the quadriceps. Research support for this hypothesis, however, is equivocal. Therefore, the purposes of this study were 1) to determine muscle recruitment patterns of the gluteus maximus, hamstrings, quadriceps, and gastrocnemius during an unloaded squat exercise via EMG and 2) to describe the amount of hamstring-quadriceps co-contraction during an unloaded squat. Surface electrodes were used to monitor the EMG activity of six muscles of 41 healthy subjects during an unloaded squat. Each subject performed three 4-s maximal voluntary isometric contractions (MVIC) for each of the six muscles. Electrogoniometers were applied to the knee and hip to monitor joint angles, and each subject performed three series of four complete squats in cadence with a metronome (50 beats.min-1). Each squat consisted of a 1.2-s eccentric, hold, and concentric phase. A two-way repeated measures ANOVA (6 muscles x 7 arcs) was used to compare normalized EMG (percent MVIC) values during each arc of motion (0-30 degrees, 30-60 degrees, 60-90 degrees, hold, 90-60 degrees, 60-30 degrees, 30-0 degrees) of the squat. Tukey post-hoc analyses were used to quantify and interpret the significant two-way interactions. Results revealed minimal hamstring activity (4-12% MVIC) as compared with quadriceps activity (VMO: 22-68%, VL: 21-63% of MVIC) during an unloaded squat in healthy subjects. This low level of hamstring EMG activity was interpreted to reflect the low demand placed on the hamstring muscles to counter anterior shear forces acting at the proximal tibia.

Adult↗

PubMed1986

Voluntary supraspinal suppression of spinal reflex activity in paralyzed muscles of spinal cord injury patients.

Having previously demonstrated that residual facilitatory brain influence on segmental structures occurs in paralyzed spinal cord injury patients, we sought evidence of suprasegmental suppression in such patients. By recording EMG activity from leg muscles, we studied changes in segmental excitability of the plantar reflex elicited by cutaneous stimulation of the plantar surface. Using surface EMG recordings, 50 paralyzed spinal cord injury patients were examined for their ability to volitionally suppress the plantar reflex on three repeated trials after three baseline trials. The patients, who had no voluntary EMG activity in the monitored muscles, were able to volitionally suppress the plantar reflex responses by 45% in the tibialis anterior, hamstring, and triceps surae muscles and to suppress the quadriceps response by 72%. In this patient group, 73 of 100 tibialis anterior muscle groups showed suppression of more than 20% compared with the control response. On reexamination, these findings were consistent during a period of 2 years in six patients. We conclude that suprasegmental suppression of segmental activity does occur in paralyzed spinal cord injury patients, and that in clinically complete patients, neurological evaluation should include assessment of the degree of preservation of suprasegmental neurocontrol on segmental activity below the lesion.

Adolescent↗

PubMed2004

[Delayed post effort muscle soreness].

Muscle intolerance to exercise may result from different processes. Diagnosis involves confirming first the source of pain, then potential pathological myalgia. Delayed-onset muscle soreness (DOMS), commonly referred as tiredness, occurs frequently in sport. DOMS usually develops 12-48 h after intensive and/or unusual eccentric muscle action. Symptoms usually involve the quadriceps muscle group but may also affect the hamstring and triceps surae groups. The muscles are sensitive to palpation, contraction and passive stretch. Acidosis, muscle spasm and microlesions in both connective and muscle tissues may explain the symptoms. However, inflammation appears to be the most common explanation. Interestingly, there is strong evidence that the progression of the exercise-induced muscle injury proceeds no further in the absence of inflammation. Even though unpleasant, DOMS should not be considered as an indicator of muscle damage but, rather, a sign of the regenerative process, which is well known to contribute to the increased muscle mass. DOMS can be associated with decreased proprioception and range of motion, as well as maximal force and activation. DOMS disappears 2-10 days before complete functional recovery. This painless period is ripe for additional joint injuries. Similarly, if some treatments are well known to attenuate DOMS, none has been demonstrated to accelerate either structural or functional recovery. In terms of the role of the inflammatory process, these treatments might even delay overall recovery.

Exercise↗

PubMed2000

Muscle volume, MRI relaxation times (T2), and body composition after spaceflight.

Postflight changes in muscle volume, calf muscle transverse relaxation time, and total body composition were measured in 4 crewmembers after a 17-day mission and in 14-16 crewmembers in multiple shuttle/Mir missions of 16- to 28-wk duration. During the 17-day mission, all muscle regions except the hamstrings significantly decreased 3-10% compared with baseline. During the shuttle/Mir missions, there were significant decreases in muscle volume (5-17%) in all muscle groups except the neck. These changes, which reached a new steady state by 4 mo of flight or less, were reversed within 30-60 days after landing. Postflight swelling and elevation of calf muscle transverse relaxation time persisted for several weeks after flight, which suggests possible muscle damage. In contrast to the 17-day flight, in which loss in fat, but not lean body mass, was found (25), losses in bone mineral content and lean body mass, but not fat, were seen after the longer shuttle/Mir missions. The percent losses in total body lean body mass and bone mineral content were similar at approximately 3.4-3.5%, whereas the pelvis demonstrated the largest regional bone loss at 13%.

Adult↗

PubMed2000

Mechanisms of anterior cruciate ligament injury.

This study examined the mechanisms of anterior cruciate ligament (ACL) injury. In the first part of the study, using a comprehensive, standardized questionnaire, 89 athletes (100 knees) were interviewed about the events surrounding their ACL injury. A noncontact mechanism was reported in 71 (72%) knees and a contact injury in 28 (28%) knees; one patient was unsure if there was any contact. Most of the injuries were sustained at footstrike with the knee close to full extension. Noncontact mechanisms were classified as sudden deceleration prior to a change of direction or landing motion, while contact injuries occurred as a result of valgus collapse of the knee. Hamstring flexibility parameters revealed a statistically higher level of laxity in the injured athletes compared with a matched group of 28 controls. In the second part of the study, videotapes of 27 separate ACL disruptions were reviewed and confirmed that most noncontact injuries occur with the knee close to extension during a sharp deceleration or landing maneuver. Because the knee is in a position to allow the extensor mechanism to strain the ACL and maximum, eccentric muscle force conditions usually apply, the quadriceps may play an important role in ACL disruption. Passive protection of the ACL by the hamstring muscles may be reduced in patients with above-average flexibility.

Anterior Cruciate Ligament Injuries↗

PubMed2005

The effect of physical training on workload, upper leg muscle function and muscle areas in patients with chronic heart failure.

OBJECTIVE: To investigate the effect of physical training (PTr) on upper leg muscle area, muscle strength and muscle endurance expressed as upper leg muscle function (ULMF) in relation to exercise performance in CHF. DESIGN: Randomised to a training (TG) or control group (CG). SETTING: Outpatient cardiac rehabilitation centre of community hospital. PATIENTS: 77 CHF patients (59 men and 18 women), NYHA class II/III, age 59.8+/-9.3 years, LVEF 27+/-8%. Sixteen patients dropped out during the intervention period, 61 patients (M/F:46/15) completed the study. INTERVENTION: PTr (combined strength and endurance exercises) four times per week, twice supervised and twice at home, during 26 weeks. MAIN OUTCOME MEASURES: LVEF, body composition, daily physical activity, exercise performance, upper leg muscle area and isokinetic leg muscle variables. RESULTS: Workload and peak oxygen consumption decreased in the CG (-4.1% and -4%) but increased in the TG (+5% and +4%) following PTr (p<0.05, ANOVA repeated measures). Hamstrings area decreased in the CG and did not change in the TG (p<0.05, ANOVA repeated measures). ULMF improved in the TG, but remained unchanged in the CG (+13.0% and 0.0, respectively, p<0.05; ANOVA repeated measures). At baseline and after intervention nearly 60% of the variance in maximal workload was explained by ULMF and quadriceps muscle area (multiple regression analysis). CONCLUSIONS: In CHF patients, home-based training in conjunction with a supervised strength and endurance training program is safe, feasible and effective and does not require complex training equipment. Physical training prevented loss of hamstrings muscle mass and improved exercise performance by enhancing muscle strength and endurance.

Exercise↗

PubMed2004

Effects of Plyometric Training on Muscle-Activation Strategies and Performance in Female Athletes.

OBJECTIVE: To evaluate the effects of plyometric training on muscle-activation strategies and performance of the lower extremity during jumping exercises. SUBJECTS: Twenty healthy National Collegiate Athletic Association Division I female athletes. DESIGN AND SETTING: A pretest and posttest control group design was used. Experimental subjects performed plyometric exercises 2 times per week for 6 weeks. MEASUREMENTS: We used surface electromyography to assess preparatory and reactive activity of the vastus medialis and vastus lateralis, medial and lateral hamstrings, and hip abductors and adductors. Vertical jump height and sprint speed were assessed with the VERTEC and infrared timing devices, respectively. RESULTS: Multivariate analyses of variance revealed significant (P <.05) increases in firing of adductor muscles during the preparatory phase, with significant interactions for area, mean, and peak. A Tukey honestly significant difference post hoc analysis revealed significant increases in preparatory adductor area, mean, and peak for experimental group. A significant (P =.037) increase in preparatory adductor-to-abductor muscle coactivation in the experimental group was identified, as well as a trend (P =.053) toward reactive quadriceps-to- hamstring muscle coactivation in the experimental group. Pearson correlation coefficients revealed significant between-groups adaptations in muscle activity patterns pretest to posttest. Although not significant, experimental and control subjects had average increases of 5.8% and 2.0% in vertical jump height, respectively. CONCLUSIONS: The increased preparatory adductor activity and abductor-to-adductor coactivation represent preprogrammed motor strategies learned during the plyometric training. These data strongly support the role of hip-musculature activation strategies for dynamic restraint and control of lower extremity alignment at ground contact. Plyometric exercises should be incorporated into the training regimens of female athletes and may reduce the risk of injury by enhancing functional joint stability in the lower extremity.

Journal Article↗

PubMed2001

Quadriceps and hamstring strength changes as a function of selective dorsal rhizotomy surgery and rehabilitation.

PURPOSE: Objective measures of strength in children with cerebral palsy (CP) are needed to determine the effect that selective dorsal rhizotomy surgery (SDR) and subsequent rehabilitation have on muscle strength. This investigation quantified quadriceps and hamstring strength in children with CP pre-SDR and eight months post-SDR. METHOD: Nineteen children with CP and 20 children without disabilities (WD group) were tested with an isokinetic dynamometer. The children performed a maximum concentric contraction of the quadriceps muscles as the dynamometer moved the knee from a flexed position to an extended position at 10 degrees per second. A maximum concentric contraction of the hamstring muscles was then performed as the knee was moved from extension to flexion. Four variables were recorded from the torque-angle data; peak extension and flexion torque and extension and flexion work. RESULTS: Children with CP, both pre- and post-SDR were significantly weaker in all strength measures compared with the WD group. Children with CP post-SDR and rehabilitation had significantly greater peak torque and work values compared with their pre-SDR values. The results agreed with previous studies indicating that children with CP are weaker than their peers without disabilities. Previous studies on strength changes after SDR remain controversial. CONCLUSIONS: The results of this study showed a significant increase in strength at the knee after rhizotomy and rehabilitation.

Journal Article↗

PubMed1984

Crossed actions of group I muscle afferents in the cat.

Reflex actions evoked by electrical stimulation of contralateral quadriceps, hamstring and gastrocnemius-soleus muscle afferents were investigated using intracellular recording from motoneurones, in chloralose-anaesthetized, acute, low spinal cats. Contralateral group I afferents were found to evoke excitatory post-synaptic potentials only occasionally. Contralateral group II afferents evoked post-synaptic potentials (excitatory to extensor motoneurones and inhibitory to flexor motoneurones) from the quadriceps nerve, whereas contralateral group III afferents evoked post-synaptic potentials (with the same pattern as quadriceps group II) from all muscles tested. Contralateral group I afferents were found to facilitate Ia reciprocal inhibition, and both the excitatory and inhibitory reflex actions from Ib afferents. This is taken to indicate an action of these afferents on interneurones interposed in ipsilateral reflex pathways.

Action Potentials↗

PubMed2000

Passive energy absorption by human muscle-tendon unit is unaffected by increase in intramuscular temperature.

The present study measured hamstring intramuscular temperature and muscle-tendon unit viscoelastic properties in healthy young men before and after 10 and 30 min of running with (day S) or without stretch (day NS). On day NS, passive energy absorption and intramuscular temperature were measured before running (Preex), after 10 min of running at 70% of maximum O(2) uptake (Postex10), and after 30 min of running at 75% of maximum O(2) uptake (Postex30). On day S, the protocol was repeated with three stretches (stretches 1-3) added after Postex10. Intramuscular temperature was elevated Postex10 (P < 0.01) and further Postex30 (P < 0.05). On day NS, the total energy absorbed Preex (14.3 +/- 2.3 J), Postex10 (14.5 +/- 3.2 J), and Postex30 (13.5 +/- 2.4 J) was not different. On day S, the total energy absorbed in stretch 3 (10.8 +/- 1.8 J) was lower than that Preex (14.5 +/- 1.7 J, P < 0.01) and Postex10 (13.5 +/- 1.9 J, P < 0.05) but not Postex30 (13.3 +/- 1.8 J). The total energy absorbed Postex30 did not differ from Preex. In conclusion, warm-up and continuous running elevated intramuscular temperature but did not affect the passive energy absorption. Repeated passive stretching reduced the energy absorption immediately; however, the effect did not remain after 30 min of running. These data suggest that passive energy absorption of the human skeletal muscle is insensitive to physiological increases in intramuscular temperature.

Adult↗

PubMed1998

The role of afferent feedback in the control of hamstrings activity during human gait.

In vertebrates, possibly also in man, the pattern of activation of muscles during locomotion can be generated by the spinal cord (locomotor CPG, central pattern generator). However, sensory feedback is crucial to adapt the functioning of the CPG to the external requirements during gait. It is postulated that afferent input from skin and muscles can contribute to the EMG activation patterns as observed in various limb muscles during gait. The activity of the hamstrings at end swing may be partially due to stretch reflexes of these muscles. At end stance the hamstring activity may be assisted by reflexes from natural skin activation from the dorsum of the foot. In addition, more specific actions are also incorporated. For example, sural nerve stimulation induces an activation of biceps femoris (BF) whereas a suppression is usually obtained for semitendinosus (ST), indicating that the induced activation is aimed at exorotation of the lower leg. Similarly, the preferential activation of medial versus lateral gastrocnemius (GM versus GL) in sural nerve induced reflexes could favor such exorotation. It is concluded that the present evidence points towards a possible contribution of various reflexes to the motor output seen during gait for movements both inside and outside the sagittal plane.

Afferent Pathways↗

PubMed2001

Timing of activation of the erector spinae and hamstrings during a trunk flexion and extension task.

STUDY DESIGN: Timing of activation of the hamstrings and erector spinae was assessed using surface electromyography. OBJECTIVES: To investigate the influence of posture and movement speed during trunk flexion-extension on the flexion-relaxation response and trunk muscle activation patterns. SUMMARY OF BACKGROUND DATA: The literature contains numerous reports on coactivity and synergistic behavior of major muscle groups during trunk flexion-extension. There are few reports on the timing of muscle activation. METHODS: Six subjects were recruited for a training session and six biweekly test sessions. Ten surface electromyogram electrodes and a lordosimeter were used to record timing of lumbar motion and muscle recruitment in the hamstrings and at four sites in the thoracolumbar region. A 3 x 2 within-subject factorial design was used to test the effects of posture and speed on activation patterns. RESULTS: Patterns of muscle activation were found to be dependent on posture and the direction of movement. The flexion-relaxation response was pervasive in the lumbar region but was less consistent at the T9 and hamstring sites. Significant differences in the delay between electromyogram activation and lumbar motion were found for the standing postures at initiation of extension, in which activation progressed in the caudad-to-cephalad direction. CONCLUSIONS: The flexion-relaxation response is ubiquitous in the lumbar erector spinae and is present in the hamstrings and lower thoracic erector spinae, although not consistently in all subjects. In standing, timing of activation differed significantly by site in extension but not in flexion. Muscle activation patterns and flexion-relaxation were consistent over six biweekly test sessions.

Adult↗

PubMed1985

Surface EMG profiles during different walking cadences in humans.

The ensemble electromyogram (EMG) patterns associated with different walking cadences were examined in 11 normal subjects. Five muscle groups were studied: the rectus femoris, vastus lateralis, lateral hamstring, tibialis anterior and soleus muscles of the right lower extremity. The myoelectric signals were telemetered, full-wave rectified and smoothed. Subjects walked at cadences of 115, 95 and 75 steps/min. Footswitches indicated the different phases of the stride. Six or more strides per subject were averaged for each cadence. Cadence-related changes in (1) mean EMG amplitude during stance, and during swing, and (2) the shape of the EMG patterns, were analyzed. One-way repeated-measures analyses of variance on the mean EMG amplitude in stance and in swing revealed significant changes with cadence (P less than 0.05) in all muscles examined. The magnitude of these changes could be related to the mechanical function of the muscles involved. The shape of the EMG patterns generally remained similar at the different cadences. The timing of EMG activity was closely related to the normalized stride time and remained invariant at different cadences.

Adolescent↗

PubMed2001

Atypical hamstrings electromyographic activity as a compensatory mechanism in anterior cruciate ligament deficiency.

Anterior cruciate ligament (ACL) deficiency may cause functional instability of the knee (noncopers), while other patients compensate and perform at the same level as before injury (copers). This pilot study investigated whether there is a compensatory electromyographic (EMG) activity of the hamstrings in copers, noncopers and control patients. Ten patients with an ACL deficiency were equally divided into two groups of copers and noncopers. All patients underwent gait analysis with EMG of six muscles around the knee. Ten healthy young men formed the control group. In contrast to noncopers, copers showed an atypical semitendinosus activity during stance phase; the corresponding trend was found in biceps femoris activity. There was no difference between copers and controls in knee extension during stance phase. The noncopers had less knee extension. Atypical hamstring muscle activity may thus be a compensatory mechanism by which copers enable themselves to perform on a normal level.

Adaptation, Physiological↗

PubMed1984

Electromyographic analysis of selected muscles during the lateral step-up exercise.

The purpose of this study was to determine electromyographically if significant differences in level of electrical activity in the vastus medialis, rectus femoris, biceps femoris, and semimembranosus/semitendinosus muscles occurred during the concentric and eccentric phases of a 4- and 8-in lateral step-up exercise. Twenty-nine subjects with no pathological condition of the knees participated in the study. The surface electromyograms obtained were processed by linear envelope detectors and normalized, in percentage, to a maximum voluntary contraction of each subject. Within-muscle differences, step height, and contraction type were tested with a two-way analysis of variance. Results revealed that the average values for muscular activity, depending on the height and direction, ranged from 24 percent to 60 percent for vastus medialis, 8 percent to 23 percent for rectus femoris, 3 percent to 9 percent for biceps femoris, and 4 percent to 9 percent for semimembranosus/semitendinosus muscles. All muscles were significantly more active at the 8-in height than at the 4-in height. The concentric phase produced significantly greater activity (p less than .001) than the eccentric phase at each height except for semimembranosus/semitendinosus muscles, where no significant difference existed. The results of this study are discussed with respect to the limited role that the tested hamstrings and quadriceps femoris muscles play in preventing anterior shear of the tibia during the lateral step-up exercise.

Adolescent↗

PubMed1996

Specificity of training velocity and training load on gains in isokinetic knee joint strength.

The present study investigated the effects of three different strength training regimes on the isokinetic strength profile of the knee extensors (quadriceps, Q) and flexors (hamstrings, H) and if increases in isokinetic strength were accompanied by an enhanced performance during a more complex leg movement, the soccer kick. Twenty-two elite soccer players performed 12 weeks of strength training (three times per week) at either high resistance (HR group: 4 sets, 8 reps, 8RM loading), low resistance (LR group: 4 sets, 24 reps, 24RM loading), loaded kicking movements (LK group: 4 sets, 16 reps, 16RM loading) while one group served as controls (CO group). Isokinetic concentric and eccentric moment of force was obtained (KinCom) as peak moment (Mpeak) and moment at 50 degrees knee flexion (M50) at angular velocities of 30, 120, 240 degrees s-1. Isokinetic knee joint strength was unchanged in groups LR, LK, CO. However, after the HR strength training, concentric Mpeak (+/- SD) increased (P < 0.01) at 30 degrees s-1 (Q, 258 +/- 37 to 297 +/- 57 Nm; H, 122 +/- 22 to 140 +/- 21 Nm). Furthermore, eccentric Mpeak increased at 30, 120 and 240 degrees s-1 (Q, 274 +/- 60 to 345 +/- 57 Nm (P < 0.01), 291 +/- 56 to 309 +/- 49 Nm and 275 +/- 43 to 293 +/- 36 Nm (P < 0.05), respectively; H, 143 +/- 32 to 158 +/- 25 Nm, 152 +/- 39 to 169 +/- 31 Nm and 148 +/- 27 to 163 +/- 19 Nm (P < 0.05)). Corresponding increases (P < 0.05) were observed for M50. The H/Q ratio calculated as eccentric hamstring strength divided by concentric quadriceps strength (Hecc/Qcon, representative for knee extension) at 240 degrees s-1 increased (P < 0.05) from 107 to 118% (based on Mpeak) and from 90 to 105% (M50). Kicking performance estimated by maximal ball flight velocity was unaffected by any of the strength training regimes investigated. In conclusion, only heavy-resistance strength training induced increases in isokinetic muscle strength in the absence of learning effects. Concentric strength gains were observed at the actual velocity of training, while eccentric strength gains were found over the entire range of velocities examined. The capacity of the hamstring muscles for providing stability to the knee joint during fast extension was augmented as a result of the heavy-resistance strength training. Strength training should be integrated with other types of training involving the actual movement pattern in order to increase the performance within more complex movement patterns.

Adult↗

PubMed1993

A biomechanical analysis of muscle strength as a limiting factor in standing posture.

We developed a method for studying muscular coordination and strength in multijoint movements and have applied it to standing posture. The method is based on a musculoskeletal model of the human lower extremity in the sagittal plane and a technique to visualize, geometrically, how constraints internal and external to the body affect movement. We developed an algorithm to calculate the set of all feasible accelerations (i.e., the 'feasible acceleration set', or FAS) that muscles can induce. For the ankle, knee, and hip joints in the sagittal plane, this set is a polyhedron in three dimensions. Using the volume of the FAS as an indicator of overall mobility, we found that strengthening muscles on the posterior side (as opposed to the anterior) of the body would cause greater increases in mobility. Employing the experimental observations of others, we also found that acceleration constraints greatly reduce the range of feasible accelerations. We then defined a set of four basic acceleration vectors which, when used in various combinations, can produce the repertoire of postural movements. We used linear programming to find the maximum magnitudes of these vectors, and the sensitivity of these magnitudes to muscle strength, thereby delineating those muscles which, if strengthened, would cause the greatest increase in the body's ability to generate the basic acceleration vectors. For our particular model, those muscle groups were found to be hamstrings, tibialis anterior, rectus femoris, and gastrocnemius. These muscle groups would be of great importance in cases involving severely reduced muscle strength. This methodology may therefore be useful for purposes such as design of functional electrical stimulation controllers or exercises for persons at risk for falling.

Acceleration↗

PubMed2003

Functional capability is enhanced with semitendinosus than patellar tendon ACL repair.

UNLABELLED: The patellar and semitendinosus tendon autograft are the two most common techniques that orthopedic surgeons use to reconstruct the anterior cruciate ligament (ACL). It has not been established, however, whether either of these techniques provides a greater functional advantage to the patient. PURPOSE: To identify patients' functional capabilities after reconstruction of the ACL with a patellar or semitendinosus tendon autograft. METHODS: Forty male soccer players volunteered for the study and were assigned to three homogeneous groups: individuals who had patellar tendon reconstruction (N = 15), individuals who had semitendinosus tendon reconstruction (N = 15), and a control group (N = 10). All patients had undergone surgery 2 yr before this study and received the same rehabilitation training. The testing procedures included measurement of thigh circumference, maximal isometric strength of quadriceps and hamstrings, two- and one-legged jump, squat and gait analysis. Kinetic, kinematic, and electromyographic data were collected. RESULTS: The patellar tendon group exhibited lower (P < 0.05) coactivation of the agonist and antagonist muscles around the knee joint during the squat movement and lower stabilization- and landing degrees during the jumps. Furthermore, the patellar tendon group had a shorter stance phase and reached the first vertical maximum later with the impaired leg while walking (720.2 +/- 15.6 ms vs 740.3 +/- 14.3 ms, and 24.3 +/- 0.64% vs 22.9 +/- 0.74% of stance phase), which was not observed in the semitendinosus tendon and control groups. CONCLUSION: Functional performance is compromised in patients who undergo a patellar tendon graft compared with a semitendinosus graft, possibly due to an altered activation of the quadriceps and hamstring muscles.

Adult↗