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Biomedical subjects

A Thorstensson

Publications and source records attributed to A Thorstensson.

At least 73 records · Page 4Linked to original sources
PubMed1987

Fibre types in human lumbar back muscles.

The distribution of histochemically identified muscle fibre types was studied in biopsy samples from the two main muscles in the lumbar region of the human erector spinae, the multifidus and the longissimus, in 16 healthy subjects (nine males and seven females, age 20-30 years). Muscle fibres were classified as types I, IIA, IIB or IIC on the basis of the pH lability of their myofibrillar ATPases. There were no differences between the multifidus and the longissimus muscles in the relative occurrence of type I (62 vs. 57%), type IIA (20 vs. 22%) or type IIB fibres (18 vs. 22%), or in the absolute size of fibres (range of mean least diameters 58-66 micron). The oxidative potential (NADH-diaphorase staining intensity) was high in type I and low in type II fibres, irrespective of subgroups, in both muscles. In the females, the type I fibres occupied a relatively larger area (70-75 vs. 54-58% for the males) although the relative number of type I fibres was the same in both sexes. This was due to smaller type II fibres in the females resulting in higher type I/type II area ratios (1.70-1.90 vs. 0.88-0.92 for males). This suggests a difference in functional capacity of lumbar back muscles between males and females. On the other hand, the similarity in histochemical fibre-type distribution between the multifidus and the longissimus muscles does not give support for a functional differentiation between these two anatomically different parts of the lumbar erector spinae in man.

Adenosine Triphosphatases↗
PubMed1987

Adaptations to changing speed in human locomotion: speed of transition between walking and running.

The transition speed between walking and running was determined in 18 healthy males (23-38 years) of various statures (range of leg length 0.86-1.09 m) during acceleration and deceleration of different magnitudes (0.05-0.11 ms-2) on a motor-driven treadmill. The speed of the treadmill belt and the duration of the stance phases of each foot were recorded. A transition step was identified and the speed of transition was taken as the average speed value of the stance phase of that step. The overall mean value for the transition speed was 1.88 m s-1 (range 1.30-2.55). Deceleration resulted in a somewhat lower speed of transition than acceleration. There was a tendency towards increasing values for transition speed with increasing leg length. This could partly be explained by differences in natural frequency. The reasons for the switch between walking and running at a speed which is not extreme for either mode of progression are unclear. The subjective feeling that a transition will lead to a more comfortable situation might be based on previous experience combined with information from peripheral receptors and activity in central networks controlling locomotion.

Adult↗
PubMed1986

How is the normal locomotor program modified to produce backward walking?

The modifications occurring in the movement and muscle activity patterns of the leg when changing from forward to backward walking were studied in five healthy subjects during walking on a motor driven treadmill. Movements were recorded with a Selspot optoelectronic system and muscle activity with electromyography using surface electrodes. The movement trajectories of the leg in forward and backward walking essentially mirrored each other, even though the movements occurred in the reversed direction. The angular displacements at the hip, knee and ankle joints showed similar overall magnitude and pattern in the two situations. Most of the investigated muscles changed their pattern of activity in relation to the different movement phases. At the ankle, there was a switch between flexors and extensors with flexor activation during support in backward walking. The bursts of activity in knee extensors were prolonged and shifted to the main part of the support phase. In the hip extensors, the activity periods retained their positions relative to the leg movements, but changed function due to the reversed direction of movement. Thus, drastic changes occur in the normal locomotor program to produce a reversal of leg movements and propulsion backwards.

Adult↗
PubMed1986

Effects of moderate external loading on the aerobic demand of submaximal running in men and 10 year-old boys.

The effects of moderate external loading on the aerobic demand of submaximal running were studied in habitually active adult men (29-37 yrs) and 10 year-old boys. The load was symmetrically placed around the trunk and adjusted to correspond to 10% of body weight. Running was performed on a treadmill at 8, 10 and 11 km X h-1 (2.2, 2.8 and 3.1 m X s-1). A small, but consistent decrease in net oxygen uptake (gross oxygen uptake in ml X kg-1 X min-1 minus calculated basal metabolic rate) with load was observed in both groups at all speeds, except for the men at 8 km X h-1. The decrease was larger for the boys and tended to enhance with speed. The boys had a higher net oxygen uptake than the adults at all unladen running velocities, whereas the difference in the loaded condition was significant only at the highest speed. The decrease in net oxygen uptake with load could not be directly correlated with differences in body weight or step frequency. It is hypothesized that a difference in the utilization of muscle elastic energy could underlie part of the age and load dependent changes observed in running economy.

Adult↗
PubMed1986

Fast voluntary trunk flexion movements in standing: primary movements and associated postural adjustments.

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)

Adaptation, Physiological↗
PubMed1985

A new method to measure foot contact.

A new method to measure foot contact is described. It consists of a pressure sensitive transducer attached to one end of a flexible silicone rubber tube. A reliable indicator of foot contact is obtained with the tube glued to the outer perimeter of the sole of a shoe.

Humans↗
PubMed1985

Changes in leg movements and muscle activity with speed of locomotion and mode of progression in humans.

Knowledge of adaptations to changes in speed and mode of progression (walking-running) in human locomotion is important for an understanding of underlying neural control mechanisms and allows a comparison with more detailed animal studies. Leg movements and muscle activity patterns were studied in ten healthy males (19-29 yr) during level walking (0.4-3.0 m X s-1) and running (1.0-9.0 m X s-1) on a motor-driven treadmill. Movements were recorded in the sagittal plane with a Selspot optoelectronic system. Recordings of EMG were made from seven different muscles of one leg by means of surface electrodes. Durations, amplitudes and relative phase relationships of angular displacements and EMG activity were analysed in relation to different phases of the stride cycle (defined by the leg movements). The durations of the entire stride cycle and of the support phase were found to decrease curvilinearly with velocity. Swing and support phase durations were linearly related to cycle duration in walking, and curvilinearly related in running. The characteristic occurrence of double support phases in walking was also seen in very slow running. Support length increased with speed up to about 1.2 m both in walking and running, but was longer in walking at the same velocity. Increases in net angular displacements were largest for hip movements and for knee flexion-extension during the swing phase in running. With increasing velocity a clear shift in relative rectus femoris activity occurred from knee extension to hip flexion. Gastrocnemius lateralis (LG) was co-activated with the other leg extensors prior to foot contact in running, whereas in walking LG was not turned on until later in the support phase. The ankle flexor tibialis anterior had its main peak of activity after touch-down in walking and before touch-down in running. The same basic structure of the stride cycle as in other animals suggests similarities in the underlying neural control. Human speed adaptation is distinguished primarily by an increase in both frequency and amplitude of leg movements and by a possibility of changing between a walking and a running type of movement pattern.

Adaptation, Physiological↗
PubMed1985

Motor control of voluntary trunk movements in standing.

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.

Adult↗
PubMed1984

Trunk movements in human locomotion.

Trunk movements in the frontal and sagittal planes were studied in 10 healthy males (18-35 yrs) during normal walking (1.0-2.5 m/s) and running (2.0-6.0 m/s) on a treadmill. Movements were recorded with a Selspot optoelectronic system. Directions, amplitudes and phase relationships to the stride cycle (defined by the leg movements) were analyzed for both linear and angular displacements. During one stride cycle the trunk displayed two oscillations in the vertical (mean net amplitude 2.5-9.5 cm) and horizontal, forward-backward directions (mean net amplitude 0.5-3 cm) and one oscillation in the lateral, side to side direction (mean net amplitude 2-6 cm). The magnitude and timing of the various oscillations varied in a different way with speed and mode of progression. Differences in amplitudes and timing of the movements at separate levels along the spine gave rise to angular oscillations with a similar periodicity as the linear displacements in both planes studied. The net angular trunk tilting in the frontal plane increased with speed from 3-10 degrees. The net forward-backward trunk inclination showed a small increase with speed up to 5 degrees in fast running. The mean forward inclination of the trunk increased from 6 degrees to about 13 degrees with speed. Peak inclination to one side occurred during the support phase of the leg on the same side. Peak forward inclination was reached at the initiation of the support phase in walking, whereas in running the peak inclination was in the opposite direction at this point. The adaptations of trunk movements to speed and mode of progression could be related to changing mechanical conditions and different demands on equilibrium control due to e.g. changes in support phase duration and leg movements.

Adaptation, Physiological↗
PubMed1982

Lumbar back muscle activity in relation to trunk movements during locomotion in man.

The function of lumbar back muscles was studied by relating their activity patterns to trunk movements in 7 healthy adult males during normal walking (1.0-2.5 m/s) and running (2.0-7.0 m/s) on a treadmill. The movements of the trunk in the sagittal and frontal planes were recorded with a Selspot optoelectronic system using infrared light emitting diodes as markers. The electromyographic (EMG) activity from the two main portions of the lumbar erector spinae muscles (Multifidus and Longissimus) was recorded bilaterally with intramuscular wire electrodes. The angular displacements of the trunk showed regular oscillations, but their shape, magnitude and relation to the step cycle were different in the two planes (sagittal and frontal) and varied with speed and mode of progression. The EMG pattern in both muscles showed a bilateral cocontraction with two main bursts of activity per step cycle starting just before each foot was placed on the ground. Relating the EMG to the movements of the trunk indicated that the main function of the lumbar erector spinae muscles is to restrict excessive trunk movements. During walking this restricting action is most evident for movements in the frontal plane, whereas in running the lumbar back muscles mainly control the movements in the sagittal plane.

Adaptation, Physiological↗
PubMed1982

Trunk muscle strength and low back pain.

The strength of the trunk muscles was measured in a group of young males with low back insufficiency (n=7) and in an age matched (19-21 yrs) healthy control group (n=8). A recently designed new application of the isokinetic technique was used to record maximal torque produced by the trunk muscles during flexion, extension and lateral flexion. Trunk muscle strength was measured during isometric contractions in different trunk positions and during slow isokinetic contractions in the whole range of motion. No significant differences between the groups were observed for trunk extension, lateral flexion or flexion with the centre of rotation at L2-L3 level. However, in the initial part of isokinetic trunk flexion with the pivot point at the hip joint the strength values for the back patients were significantly lower than for the controls. The present results demonstrate the importance of a comprehensive approach to the assessment of trunk muscle strength, including different movement velocities, body positions and pivot points. Further studies are needed to evaluate the significance of the specific weakness observed in dynamic trunk flexion strength in the back patients.

Adult↗
PubMed1982

Trunk muscle strength during constant velocity movements.

A new apparatus has been designed for standardized measurements of the strength of human trunk muscles utilizing the isokinetic (constant movement velocity) technique (Cybex). It is possible to measure the produced torque during maximal voluntary isometric and isokinetic contractions in the whole range of motion during flexion, extension and lateral flexion of the trunk. Effects of gravity are eliminated since the movements are performed in the horizontal plane. Torque can be measured around different centres of rotation of the body. With this experimental set-up the strength of the trunk muscles has been characterized in a group of 14 normal male subjects (18-31 yrs). The torque produced by the trunk muscles varied with movement velocity and trunk position in the arc of motion. Peak torque occurred in a position where the muscles involved were stretched. The strength of the trunk extensors exceeded that of the flexors, but the degree (ratio) varied with trunk position. The relative contribution of the hip muscles to the total torque produced with the centre of rotation at the hip joint was larger for flexors than for extensors and varied with velocity and position. It is concluded that the present technique is useful to characterize the human trunk muscles.

Adolescent↗
PubMed1979

Fibre types in human abdominal muscles.

Histochemical muscle fibre composition was studied in biopsied from the four different muscles of the abdominal wall (rectus abdominis, RA, obliquus externus, OE, obliquus internus, OI, and transversus abdominis, Tr) in 13 normal human subjects (9 females and 4 males, age 24-55 years) undergoing gall-bladder surgery. Muscle fibres were classified as Type I, IIA, IIB or IIC on the basis of their myofibrillar ATPases' pH lability. There were large inter-individual variations in fibre composition, whereas, in general, the differences between the different muscles were minor or non-existent. Mean fibre distribution ranges were 55-58% I, 15-23% 22A, 21-28% IIB, and 0-1% II C fibres. The least fibre diameters were similar for all types and muscles (range of means 50-54 micrometer) except for Tr in which the Type II fibres were smaller (mean 45 micrometer). There was a high correlation in the size of Type I vs. II fibres and Type IIA vs. IIB fibres in all layers. The oxidative potential (NADH-diaphorase staining intensity) appeared high in Type I fibres and low in Type II fibres, irrespective of subgroups. Thus, based on histochemical fibre composition, the different abdominal muscles appear to have a similar functional capacity. However, functional differences between individuals were indicated by the large inter-individual variation in muscle fibre distribution.

Abdominal Muscles↗
PubMed1978

Intra-abdominal pressure changes during natural movements in man.

The weight of the upper part of the trunk is partially transmitted to the pelvis via the vertebral column. If the muscle walls around the abdominal cavity are contracted, a high pressure can be generated within the cavity (greater than 200 mmHg). The abdominal space can them transmit part of weight to, e.g., the upper part of the body, Intra-abdominal pressure recordings have been performed during locomotion and other natural movements with intragastric pressure recordings. With each step, there is a phasic variation in pressure, with its peak coinciding with that of the peak vertical force exerted by the leg against the ground. The peak values increase progressively with the speed of walking/running up to a mean of 38 mmHg and with trough values of 16 mmHg. The phasic variations with each step is due to a phasic activation of the abdominal muscles, with an EMG activity starting 50 ms or more before foot contact. If an extra load is put on the back, the posture changes and at the highest speed of running the pressure values are significantly higher than without this additional load. After a jump down from a moderate height of 0.4 m, the average increase is 89 mmHg and can often exceed 100 mmHg. These pressure changes are large and will presumably act to unload the spine under the prevailing biomechanical conditions and, in addition, there will no doubt be an effect on the circulatory system.

Abdomen↗
PubMed1978

Muscle fatigue and its relation to lactate accumulation and LDH activity in man.

The lactate concentration in different muscle fibre types was determined in biopsy specimens from human vastus lateralis muscle after 30 and 60 s of maximal dynamic leg exercise. In addition, muscle fibre type distribution, total lactate dehydrogenase (LDH) activity, and isozymes of LDH were determined. In accordance with previous studies (Thorstensson and Karlsson 1976, Nilsson et al. 1977) it was found that an increasing proportion of slow twitch (ST) fibres corresponded to better sustained muscle force. Lactate was found preferentially in fast twitch (FT) fibres after 30 s, but after 60 s this difference was abolished. Differences between the two main muscle fibre types in muscle lactate, total LDH activity, and M-LDH activity were correlated to muscle fatigue. It was concluded that lactate or associated pH changes primarily in FT fibres could be one factor responsible for the impaired muscle function.

Adult↗
PubMed1978

Maximal oxygen uptake and muscle fiber types in trained and untrained humans.

Maximal oxygen uptake (Vo2 max) was determined in 138 male and 41 female human subjects and muscle fiber composition (gastrocnemius and vastus lateralis) in 53 of the males. Highest values for Vo2 max were 7.38 1 x min-1 and 4.341 x min-1 in males and females, respectively. In relation to body weight the highest values were 94 and 77 ml x (kg x min)-1. Athletes participating in endurance events had very high Vo2 max and predominantly slow twitch (ST) fiber populations whereas weight lifters attained rather low values for Vo2 max and had a higher percentage of fast twitch (FT) fibers. Among subjects with the same fiber composition, Vo2 max was higher in the athletes than in the moderately trained. All groups taken together demonstrated a positive relationship between Vo2 max and the relative number of ST fibers (r = 0.67). For endurance and strength athletes r = 0.72 and for the moderately trained r = 0.34, both correlation coefficients being significant.

Body Weight↗