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| 2. |
- Moritani, T, et al.
(författare)
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Neural and biomechanical differences between men and young boys during a variety of motor tasks.
- 1989
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 137:3, s. 347-55
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Tidskriftsartikel (refereegranskat)abstract
- The adaptation in activation patterns of the ankle extensor muscles to different functional demands was studied in adult men (n = 10) and 9-year-old boys (n = 10). The relative magnitude of the activation of the slow soleus (SOL) and the relatively fast medial gastrocnemius (MG) muscle was measured during various postures and hopping tasks on a force plate. In addition, the myo-electric activity was quantified in three different phases of the stretch-shortening cycles during hopping. Major differences between boys and adults were observed in the postural tasks, where the boys appeared to utilize the MG to a relatively larger extent. During maximal height hopping there was a clearly larger potentiation of the MG activity in the adults, particularly in the eccentric phase. On the other hand, there were striking similarities between boys and adults with respect to the degree of pre-activation of both muscles during the different hopping regimes as well as potentiation of muscle activity during the concentric phase of maximal height hopping. Thus, some aspects of the selective neural control of the ankle extensor muscles appear to be manifested in pre-pubertal boys. However, the data also indicate that other factors, such as utilization of stored elastic energy in the muscles and stretch reflex potentiation, will still continue to develop from the age of nine.
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| 3. |
- Oddsson, L, et al.
(författare)
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Fast voluntary trunk flexion movements in standing : motor patterns.
- 1987
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 129:1, s. 93-106
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Tidskriftsartikel (refereegranskat)abstract
- The electromyographical (EMG) activity was studied during voluntary flexion movements of the trunk in erect standing man. The movements were performed at maximal velocity with successively increasing amplitude to cover the whole range of motion. The EMG activity was recorded from agonist-antagonist pairs of muscles at the ankle, knee, hip and trunk. The angular displacements at the corresponding joints were recorded using a Selspot optoelectronic system. The duration of initiating activity in prime movers (rectus abdominis and rectus femoris) as well as time to onset of activity in muscles braking the primary movement (erector spinae, gluteus maximus and hamstrings) were highly correlated with amplitude, duration, peak velocity and time to peak velocity of the movement (r = 0.59-0.91). The corresponding correlations for peak acceleration and deceleration of the movement were low (r = 0.03-0.38), indicating that acceleration and deceleration of a movement was not coded in the temporal aspects of the EMG. Onset of activity in rectus abdominis and rectus femoris as well as an early appearing burst of activity in vastus lateralis were invariant in relation to start of movement over the whole movement range. In the initial phase of a fast trunk flexion, activity in tibialis anterior appeared successively earlier with increasing movement amplitude. This resulted in a changed order of activation for the muscles from proximal to distal (rectus abdominis first) to distal to proximal (tibialis anterior first). Two different forms of associated postural adjustments are present during a fast trunk flexion, one early fast knee flexion and a later slower angle extension. Prior to knee flexion, no activity was recorded from muscles flexing at the knee implying that some other force must create a flexing torque around the knee. It is suggested that activity in rectus abdominis initiating the primary movement also initiates knee flexion through the upward pulling of pelvis. This would be possible since rectus femoris stabilizes the pelvis in relation to the leg, allowing the force in rectus abdominis to be transmitted below the hip joint and act extending around the ankle joint. However, when tibialis anterior is activated it stabilizes the shank which in turn will cause a knee flexion controlled by a lengthening contraction in vastus lateralis. During the subsequent ankle extension activity appears in lateral gastrocnemius and soleus causing the associated postural adjustment at the ankle. It can be concluded that activation of postural muscles prior to prime mover muscles is not always necessary.(ABSTRACT TRUNCATED AT 400 WORDS)
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- Oddsson, L, et al.
(författare)
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Fast voluntary trunk flexion movements in standing : primary movements and associated postural adjustments.
- 1986
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 128:3, s. 341-9
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Tidskriftsartikel (refereegranskat)abstract
- Movement patterns were studied during fast voluntary forward flexions of the trunk from an erect standing position. Three healthy subjects performed three series of six consecutive trunk flexions at maximum velocity and with successively increasing amplitude, covering a major part of the range of motion (range for all subjects: 13-97 degrees). Angular displacements of the trunk, hip, knee and ankle were measured together with the tilt of the pelvis and the flexion of the spine using a Selspot optoelectronic system. Trunk flexion was the result of a simultaneous forward pelvic tilt and flexion of the spine. For trunk movements up to 55 degrees, spine flexion dominated the movement, whereas for larger movements a major part of the amplitude was caused by pelvic tilt. During flexion of the trunk a simultaneous hip flexion and ankle extension was seen. At the knee there was an initial flexion and a subsequent extension. The net amplitude of the knee flexion showed a negative correlation with net trunk flexion amplitude for movements up to 50 degrees, whereas for larger amplitudes the correlation was positive. Time from onset of the trunk movement to peak knee flexion showed a weak correlation to net trunk flexion amplitude (r = 0.34) whereas the corresponding correlation was higher for pelvic tilt, spine flexion, hip flexion, ankle extension, and knee extension (r = 0.60-0.91). Each successive trial during a series of trunk movements was started from an increasing degree of knee flexion. This gradual adaptation was also present when successive trunk flexions were performed with constant movement amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 5. |
- Oddsson, L, et al.
(författare)
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Task specificity in the control of intrinsic trunk muscles in man.
- 1990
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 139:1, s. 123-31
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Tidskriftsartikel (refereegranskat)abstract
- The human trunk is a complex mechanical system comprised of large and small segments interconnected with several layers of muscles. An accurate control of this system is important during a variety of everyday tasks such as voluntary movements of the trunk, walking and running. This study was designed to investigate the interaction between muscles controlling the pelvis and the trunk during a variety of movements requiring a finely tuned coordination. Four subjects carried out seven different forms of fast oscillatory movements of the pelvis and trunk in the sagittal and transverse planes. Electromyographical activity (EMG) was recorded with surface electrodes from the abdominal muscles rectus abdominis (RA), obliquus externus (OE), obliquus internus (OI), and erector spinae (ES), from the hip flexor muscle rectus femoris (RF), the hip extensor muscle gluteus maximus (GM) and from the hip extensor/knee flexor muscles of the hamstrings group (HAM). Movements were recorded with an optoelectronic system (Selspot). The results indicate that during spontaneous flexion-extension movements of the trunk there was a basic alternating activation between a pure flexor (RF-RA-OE-OI) and an extensor synergy (ES-GM-HAM). Different mixed synergies appeared when more specific patterns of coordination of the pelvis and spine were performed. For example, during pelvic tilts in the sagittal plane, RA-OE-OI-GM formed a synergy which was activated reciprocally with ES. The neural circuitry controlling muscles of the pelvis and trunk is apparently adaptable to a variety of different tasks. Individual muscles were shown to either cause, brake or prevent a movement and to be integrated in several different task-specific motor synergies.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 6. |
- Thorstensson, Alf, et al.
(författare)
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Motor control of voluntary trunk movements in standing.
- 1985
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 125:2, s. 309-21
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Tidskriftsartikel (refereegranskat)abstract
- The pattern of activity in different trunk muscles during voluntary trunk movements was studied in the standing position in man. The electromyographic activity from ventral and dorsal trunk muscles on the left and right sides were recorded together with the movements in the sagittal and frontal planes (Selspot optoelectronic system). Movement direction, amplitude, velocity and initial posture were varied. In all movements there was a basic pattern of alternation between antagonist muscle groups. Fast movements were initiated by a sharp burst of activity, whereas slow flexions and side bendings resulted from a decrease in antigravity muscle activity. Movement amplitude was related to the magnitude of the initiating burst, and also to the time of onset of antagonist muscle activity with a braking effect. The contribution of passive internal forces in the braking of a movement was indicated by the myoelectrical pattern of activity, particularly in slow large side bendings, where ipsilateral activity was present at the end of the movement. Sagittal movements starting at different initial trunk inclinations resulted in shifts in onset time and duration between antagonist muscles. The observed modifications are specific adaptations of the motor program to balance changes in mechanical conditions, such as angular acceleration, moment arm for the gravitational force, and intrinsic forces of active and passive structures surrounding the spine and pelvis. In conclusion, the present results demonstrate that trunk movements are generated and controlled by specific patterns of muscle coordination.
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