Explanations pertaining to the hip joint flexor moment during the stance phase of human walking.

A hip joint flexor moment in the last half of the stance phase during walking has repeatedly been reported. However, the purpose of this moment remains uncertain and it is unknown how it is generated. Nine male subjects were instructed to walk at 4.

Antagonist muscle moment is increased in ACL deficient subjects during maximal dynamic knee extension.

Introduction: Coactivation of the hamstring muscles during dynamic knee extension may compensate for increased knee joint laxity in anterior cruciate ligament (ACL) deficient subjects. This study examined if antagonist muscle coactivation during maximal dynamic knee extension was elevated in subjects with anterior cruciate ligament (ACL) deficiency compared to age-matched healthy controls.

Methods: Electromyography (EMG) and net knee joint moments were recorded during maximal concentric quadriceps and eccentric hamstring contractions, performed in an isokinetic dynamometer (ROM: 90-10°, angular speed: 30°/s).

Absence of sensory function in the reconstructed anterior cruciate ligament.

Cruciate ligaments provide sensory information that cause excitatory as well as inhibitory effects to the activity of the muscles around the knee. The aim of the study was to determine whether these muscular reflexes are reestablished after anterior cruciate ligament (ACL) re-construction. Wire electrodes were inserted during arthroscopy into the normal posterior cruciate ligament (PCL) and the reconstructed ACL in 11 patients who had a successful ACL re-construction 8 months to 12 years earlier.

Test-retest reliability of the soleus H-reflex excitability measured during human walking.

The purpose of the study was to investigate with what accuracy the soleus H-reflex modulation and excitability could be measured during human walking on two occasions separated by days. The maximal M-wave (Mmax) was measured at rest in the standing position. During treadmill walking every stimulus elicited an M-wave of 25 ± 10% of Mmax in the soleus muscle and a supra-maximal stimulus elicited a maximal M-wave 60 ms after the first stimulus.

Phase-dependent modulation of percutaneously elicited multisegmental muscle responses after spinal cord injury.

Phase-dependent modulation of monosynaptic reflexes has been reported for several muscles of the lower limb of uninjured rats and humans. To assess whether this step-phase-dependent modulation can be mediated at the level of the human spinal cord, we compared the modulation of responses evoked simultaneously in multiple motor pools in clinically complete spinal cord injury (SCI) compared with noninjured (NI) individuals. We induced multisegmental responses of the soleus, medial gastrocnemius, tibialis anterior, medial hamstring, and vastus lateralis muscles in response to percutaneous spinal cord stimulation over the Th11-Th12 vertebrae during standing and stepping on a treadmill.

The influence of experimentally induced pain on shoulder muscle activity.

Muscle function is altered in painful shoulder conditions. However, the influence of shoulder pain on muscle coordination of the shoulder has not been fully clarified. The aim of the present study was to examine the effect of experimentally induced shoulder pain on shoulder muscle function.

Forward lunge as a functional performance test in ACL deficient subjects: test-retest reliability.

The forward lunge movement may be used as a functional performance test of anterior cruciate ligament (ACL) deficient and reconstructed subjects. The purposes were 1) to determine the test-retest reliability of a forward lunge in healthy subjects and 2) to determine the required numbers of repetitions necessary to yield satisfactory reliability. Nineteen healthy subjects performed four trials of a forward lunge on two different days.

The activity pattern of shoulder muscles in subjects with and without subacromial impingement.

Altered shoulder muscle activity is frequently believed to be a pathogenetic factor of subacromial impingement (SI) and therapeutic interventions have been directed towards restoring normal motor patterns. Still, there is a lack of scientific evidence regarding the changes in muscle activity in patients with SI. The aim of the study was to determine and compare the activity pattern of the shoulder muscles in subjects with and without SI.

Modulation of multisegmental monosynaptic responses in a variety of leg muscles during walking and running in humans.

Motor responses evoked by stimulating the spinal cord percutaneously between the T11 and T12 spinous processes were studied in eight human subjects during walking and running. Stimulation elicited responses bilaterally in the biceps femoris, vastus lateralis, rectus femoris, medial gastrocnemius, soleus, tibialis anterior, extensor digitorum brevis and flexor digitorum brevis. The evoked responses were consistent with activation of Ia afferent fibres through monosynaptic neural circuits since they were inhibited when a prior stimulus was given and during tendon vibration.

The effect of handedness on electromyographic activity of human shoulder muscles during movement.

The aim of the study was to investigate whether there was a difference in the electromyographic (EMG) activity of human shoulder muscles between the dominant and nondominant side during movement and to explore whether a possible side-difference depends on the specific task. We compared the EMG activity with surface and intramuscular electrodes in eight muscles of both shoulders in 20 healthy subjects whose hand preference was evaluated using a standard questionnaire. EMG signals were recorded during abduction and external rotation.

Reflexes in the shoulder muscles elicited from the human coracoacromial ligament.

Morphological studies have demonstrated mechanoreceptors in the capsuloligamentous structures of the shoulder joint, however knowledge of the role these joint receptors play in the control of shoulder stability is limited. We therefore investigated the effect of electrically induced afferent activity from mechanoreceptors in the coracoacromial ligament (CAL) on the activity of voluntary activated shoulder muscles in healthy humans. In study I, wire electrodes, for electrical stimulation, were inserted into the CAL in eight normal shoulders.

Evaluation of the walking pattern in two types of patients with anterior cruciate ligament deficiency: copers and non-copers.

The purpose of the present study was to investigate whether different walking patterns in healthy subjects and in coper and non-coper subjects with deficient anterior cruciate ligaments could be quantified. An inverse dynamics approach was used to calculate joint kinematics and kinetics for flexion and extension. EMG signals of the hamstrings and quadriceps muscles were recorded.

Differences in the movement pattern of a forward lunge in two types of anterior cruciate ligament deficient patients: copers and non-copers.

Objective: To determine whether differences in the knee joint movement pattern of a forward lunge could be quantified in healthy subjects and in anterior cruciate ligament deficient subjects who were able to return to the same activity level as before their injury (copers) and in those who were not (non-copers).

Design: The movement patterns of the injured leg of the coper and non-coper anterior cruciate ligament deficient subjects and the right leg of the control subjects were compared statistically.

Background: The forward lunge seems to be a less stressful test than the commonly used one-legged hop test, which makes it a possible tool for evaluating and comparing the functional performance of non-copers and copers.

Increased rate of force development and neural drive of human skeletal muscle following resistance training.

The maximal rate of rise in muscle force [rate of force development (RFD)] has important functional consequences as it determines the force that can be generated in the early phase of muscle contraction (0-200 ms). The present study examined the effect of resistance training on contractile RFD and efferent motor outflow ("neural drive") during maximal muscle contraction. Contractile RFD (slope of force-time curve), impulse (time-integrated force), electromyography (EMG) signal amplitude (mean average voltage), and rate of EMG rise (slope of EMG-time curve) were determined (1-kHz sampling rate) during maximal isometric muscle contraction (quadriceps femoris) in 15 male subjects before and after 14 wk of heavy-resistance strength training (38 sessions).

H reflexes recorded during locomotion.

We recorded H reflexes and the biomechanics of movement during locomotion. The soleus H reflex was strongly modulated during normal walking, depressed during the swing phase and modulated with the EMG in the stance phase. The amplitude of the H reflex increased with the EMG activity and was larger during running than walking.

Shoulder reflexes.

Dynamic shoulder stability is dependent on muscular coordination and sensory inputs. In the shoulder, mechanoreceptors are found in the coracoacromial ligament, the rotator cuff tendons, the musculotendinous junctions of the rotator cuff and in the capsule. The number of receptors in the capsule is small compared to the number in the other shoulder structures.

Cruciate ligament reflexes.

The idea of muscular reflexes elicited from sensory nerves of the cruciate ligaments is more than 100 years old, but the existence of such reflexes has not been proven until the recent two decades. First in animal experiments, a muscular excitation could be elicited in the hamstrings when the anterior cruciate ligament (ACL) was pulled, and tension in the ligament caused activity of the gamma motor neurones of the muscles around the knee. Impulses from the sensory nerves in ACL were activated during motion of the knee, in particular overstretching and combined extension and rotation.

Neural adaptation to resistance training: changes in evoked V-wave and H-reflex responses.

Combined V-wave and Hoffmann (H) reflex measurements were performed during maximal muscle contraction to examine the neural adaptation mechanisms induced by resistance training. The H-reflex can be used to assess the excitability of spinal alpha-motoneurons, while also reflecting transmission efficiency (i.e.

Interindividual differences in H reflex modulation during normal walking.

Based on previous studies, at least two different types of soleus Hoffmann (H) reflex modulation were likely to be found during normal human walking. Accordingly, the aim of the present study was to identify different patterns of modulation of the soleus H reflex and to examine whether or not subjects with different H reflex modulation would exhibit different walking mechanics and different EMG activity. Fifteen subjects walked across two force platforms at 4.