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Helene Pedersen, Atle Hole Saeterbakken, Markus Vagle, Marius Steiro Fimland and Vidar Andersen

that different exercises have different regional activating patterns, 4 with the NHE having a homogenous regional activating pattern, with the semitendinosus being more activated in the proximal region, while the biceps femoris is more activated in the distal region. 5 This could be of importance

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Allyson M. Carter, Stephen J. Kinzey, Linda F. Chitwood and Judith L Cole

Context:

Proprioceptive neuromuscular facilitation (PNF) is commonly used before competition to increase range of motion. It is not known how it changes muscle response to rapid length changes.

Objective:

To determine whether PNF alters hamstring muscle activity during response to rapid elongation.

Design:

2 X 2 factorial.

Setting:

Laboratory.

Participants:

Twenty-four women; means: 167.27 cm, 58.92 kg, 21.42 y, 18.41% body fat, 21.06 kg/m2 BMI.

intervention:

Measurements before and after either rest or PNF were compared.

Main Outcome Measures:

Average muscle activity immediately after a rapid and unexpected stretch, 3 times pretreatment and posttreatment, averaged into 2 pre-and post- measures.

Results:

PNF caused decreased activity in the biceps femoris during response to a sudden stretch (P = .04). No differences were found in semitendinosus activity (P = .35).

Conclusions:

Decreased muscle activity likely results from acute desensitization of the muscle spindle, which might increase risk of muscle and tendon injury.

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Grant E. Norte, Katherine R. Knaus, Chris Kuenze, Geoffrey G. Handsfield, Craig H. Meyer, Silvia S. Blemker and Joseph M. Hart

directed toward knee-extensor muscular impairments associated with bone-patellar tendon-bone autograft, morphological changes related to long-term outcomes have been observed in the knee flexors of patients with semitendinosus–gracilis (STG) tendon autograft. 22 However, these studies are nearly

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Neal R. Glaviano and David M. Bazett-Jones

, biceps femoris, semitendinosus, and adductor longus. Electrode placement was completed with palpation of the muscle bellies during submaximal isometric voluntary contractions. Skin was shaved, cleansed with isopropyl alcohol, and debrided with gauze. Electrodes were placed on both the superior and

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Nadège Tebbache and Alain Hamaoui

), erector spinae in the lumbar region (ES L3), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF), semitendinosus (ST), gluteus maximus (GluM), gastrocnemius medialis (GM), tibialis anterior (TA), and soleus (Sol). Electromyograms were obtained using Ag/AgCl pregelled disposable electrodes

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Hong-Wen Wu, Cheng-Feng Tsai, Kai-Han Liang and Yi-Wen Chang

muscle activation. The skin was shaved and cleaned with alcohol cotton to reduce the skin impedance. The testing muscles consisted of vastus medialis, rectus femoris, vastus lateralis, biceps femoris, semitendinosus, tibialis anterior, gastrocnemius lateralis, and medialis in the dominant leg. The EMG

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Denys Batista Campos, Isabella Christina Ferreira, Matheus Almeida Souza, Macquiden Amorim Jr, Leonardo Intelangelo, Gabriela Silveira-Nunes and Alexandre Carvalho Barbosa

semitendinosus: 11 [2.5] vs 8 [2.3] N/μV/s [ F  = 9.13; P  = .005; ES = 1.2]). The eccentric phase analysis showed the same behavior for all muscles with significantly higher values for the H-ACC (rectus femoris: 98 [22] vs 77 [18] [ F  = 8.83; P  = .006; ES = 1.07], vastus medialis: 30 [5] vs 22 [5] N

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Ram Haddas, Steven F. Sawyer, Phillip S. Sizer, Toby Brooks, Ming-Chien Chyu and C. Roger James

Introduction:

Recurrent lower back pain (rLBP) and neuromuscular fatigue are independently thought to increase the risk of lower extremity (LE) injury. Volitional preemptive abdominal contraction (VPAC) is thought to improve lumbar spine and pelvis control in individuals with rLBP. The effects of VPAC on fatigued landing performance in individuals with rLBP are unknown.

Objectives:

To determine the effects of VPAC and LE fatigue on landing performance in a rLBP population.

Design:

Cross-sectional pretest-posttest cohort control design.

Setting:

A clinical biomechanics laboratory.

Subjects:

32 rLBP (age 21.2 ± 2.7 y) but without current symptoms and 33 healthy (age 20.9 ± 2.3 y) subjects.

Intervention(s):

(i) Volitional preemptive abdominal contraction using abdominal bracing and (ii) fatigue using submaximal free-weight squat protocol with 15% body weight until task failure was achieved.

Main Outcome Measure(s):

Knee and ankle angles, moments, electromyographic measurements from semitendinosus and vastus medialis muscles, and ground reaction force (GRF) were collected during 0.30 m drop-jump landings.

Results:

The VPAC resulted in significantly earlier muscle onsets across all muscles with and without fatigue in both groups (mean ± SD, 0.063 ± 0.016 s earlier; P ≤ .001). Fatigue significantly delayed semitendinosus muscle onsets (0.033 ± 0.024 s later; P ≤ .001), decreased GRF (P ≤ .001), and altered landing kinematics in a variety of ways. The rLBP group exhibited delayed semitendinosus and vastus medialis muscle onsets (0.031 ± 0.028 s later; P ≤ .001) and 1.8° less knee flexion at initial contact (P ≤ .008).

Conclusion:

The VPAC decreases some of the detrimental effects of fatigue on landing biomechanics and thus may reduce LE injury risk in a rLBP population.

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Yukio Urabe, Mitsuo Ochi and Kiyoshi Onari

Objective:

To investigate changes in muscle strength in the lower extremity after ACL reconstruction.

Design:

Prospective case series.

Dependent Variables:

Isokinetic muscle strength measured in 6 movements (hip extension/flexion, hip adduction/abduction, knee extension/flexion) and circumference of the thigh/calf.

Setting:

Clinic and home.

Patients:

44 (24 men, 20 women) between the ages of 16 and 47 years with an ACL rupture. All underwent reconstruction via a semitendinosus autograft.

Main Outcome Measures:

The peak torque for each joint movement was recorded. Repeated-measures ANOVA and power analysis were conducted to detect significant interaction effects.

Results:

The decline of muscle strength after ACL reconstruction remained not only in the knee extensors and flexors but also in the hip adductors.

Conclusion:

Rehabilitation programs that address the behavioral patterns and physiological characteristics of an ACL injury will benefit the athlete’s whole body and lead to a full recovery.

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Igor Setuain, Mikel Izquierdo, Fernando Idoate, Eder Bikandi, Esteban M. Gorostiaga, Per Aagaard, Eduardo L. Cadore and Jesús Alfaro-Adrián

Context:

The muscular function restoration related to the type of physical rehabilitation followed after anterior cruciate ligament reconstruction (ACLR) using autologous hamstring tendon graft in terms of strength and cross-sectional area (CSA) remain controversial.

Objective:

To analyze the CSA and force output of quadriceps and hamstring muscles in subjects following either an Objective Criteria-Based Rehabilitation (OCBR) algorithm or the usual care (UCR) for ACL rehabilitation in Spain, before and 1 year after undergoing an ACLR.

Design:

Longitudinal clinical double-blinded randomized controlled trial.

Setting:

Sports-medicine research center.

Patients:

40 recreational athletes (30 male, 10 female [24 ± 6.9 y, 176.55 ± 6.6 cm, 73.58 ± 12.3 kg]).

Intervention:

Both groups conducted differentiated rehabilitation procedures after ACLR. Those belonging to OCBR group were guided in their recovery according to the current evidence-based principles. UCR group followed the national conventional approach for ACL rehabilitation.

Main Outcome Measures:

Concentric isokinetic knee joint flexor-extension torque assessments at 180°/s and Magnetic Resonance Imaging (MRI) evaluations were performed before and 12 months after ACLR. Anatomical muscle CSA (mm2) was assessed, in Quadriceps, Biceps femoris, Semitendinous, Semimembranosus, and Gracilis muscles at 50% and 70% femur length.

Results:

Reduced muscle CSA was observed in both treatment groups for Semitendinosus and Gracilis 1 year after ACLR. At 1-year follow-up, subjects allocated to the OCBR demonstrated greater knee flexor and extensor peak torque values in their reconstructed limbs in comparison with patients treated by UCR.

Conclusions:

Objective atrophy of Semitendinosus and Gracilis muscles related to surgical ACLR was found to persist in both rehabilitation groups. However, OCBR after ACLR lead to substantial gains on maximal knee flexor strength and ensured more symmetrical anterior-posterior laxity levels at the knee joint.