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Biomedical subjects

R Nisell

Publications and source records attributed to R Nisell.

29 records · Page 2Linked to original sources
PubMed1986

Quantified electromyography of lower-limb muscles during level walking.

The electromyography (EMG) of eleven different lower limb muscles of ten healthy subjects was quantified during normal level walking. The surface EMGs obtained were normalized, in percentage, to the activity obtained during an isometric maximum voluntary test contraction of each subject. The mean peak activities of the gluteus maximus, gluteus medius, rectus femoris, vastus medialis, vastus lateralis, biceps femoris and medial hamstring muscles occurred at heel-strike and were between 5 and 15% of max isometric EMG. The magnitudes of tibialis anterior and triceps surae muscular activity were higher than those of the other muscles investigated. Mean peak activity in tibialis anterior was 27%, in gastrocnemius medialis 42%, in gastrocnemius lateralis 19% and in soleus 40%. The important role of the triceps surae during walking was reflected in comparatively high muscular activity at push-off.

Adult↗
PubMed1986

Load moments about the hip and knee joints during ergometer cycling.

The aim of the study was to calculate the magnitudes of moments of force acting about the bilateral hip and knee joint axes during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at different workloads, pedalling rates, saddle heights and pedal foot position. During cycling at 120 Watts, 60 revolutions per minute with mid-saddle height and anterior pedal foot position, the mean peak flexing and extending hip load moments were 34.3 and 8.9 Nm, respectively. Mean peak flexing knee load moments was 28.8 Nm and extending moment was 11.9 Nm. Hip load moments were significantly increased by increasing the ergometer workload or pedalling rate. For knee load moments, workload was the most important factor. The flexing knee load moment did not change with changes in pedalling rate. Different saddle heights or pedal food positions had a slight but not always statistically significant influence on the hip and knee joint loads. The maximum hip and knee joint load moments induced during cycling were small compared with those obtained during other exercises or normal activities such as level walking, stair climbing, and lifting.

Adult↗
PubMed1985

The forces of ankle joint structures during ergometer cycling.

The ankle joint moment, joint compressive force, and Achilles tendon force obtained during ergometer cycling were calculated by using a quartz force-measuring transducer mounted on the pedal. Six healthy subjects rode in 11 different ways at different workloads, pedalling rates, saddle heights, and pedal foot positions. The mean maximum dorsiflexing load moment about the ankle joint during standardized ergometer cycling was calculated to 30.9 nm. The mean ankle joint compressive force and mean Achilles tendon force measured 1008 N (1.4 times body weight) and 762 N (1.1 times body weight), respectively. The ankle joint moment was significantly changed by a change of workload or pedal foot position.

Achilles Tendon↗
PubMed1985

Mechanics of the knee. A study of joint and muscle load with clinical applications.

The load moment of force about the knee joint during machine milking and when lifting a 12.8 kg box was quantified using a computerized static sagittal plane body model. Surface electromyography of quadriceps and hamstrings muscles was normalized and expressed as a percentage of an isometric maximum voluntary test contraction. Working with straight knees and the trunk flexed forwards induced extending knee load moments of maximum 55 Nm. Lifting the box with flexed knees gave flexing moments of 50 Nm at the beginning of the lift, irrespective of whether the burden was between or in front of the feet. During machine milking, a level difference between operator and cow of 0.70 m - 1.0 m significantly lowered the knee extending moments. To quantify the force magnitudes acting in the tibio-femoral and patello-femoral joints, a local biomechanical model of the knee was developed using a combination of cadaver knee dissections and lateral knee radiographs of healthy subjects. The moment arm of the knee extensor was significantly shorter for women than for men, which resulted in higher knee joint forces in women if the same moment was produced. A diagram for quantifying patellar forces was worked out. The force magnitudes given by the knee joint biomechanical model correlated well with experimentally forces measured by others. During the parallel squat in powerlifting, the maximum flexing knee load moment was estimated to 335-550 Nm when carrying a 382.5 kg burden and the in vivo force of a complete quadriceps tendon-muscle rupture to between 10,900 and 18,300 N. During isokinetic knee extension, the tibio-femoral compressive force reached peak magnitudes of 9 times body weight and the anteroposterior shear force was close to 1 body weight at knee angles straighter than 60 degrees, indicating that high forces stress the anterior cruciate ligament. A proximal resistance pad position decreased the shear force considerably, and this position is recommended in early rehabilitation after anterior cruciate ligament repairs or reconstructions. The methods presented quantify muscle activity, sagittal knee joint moments and forces, enabling assessments to be made of different work postures, training exercises and joint derangements.

Adult↗
PubMed1985

Muscular activity during ergometer cycling.

The aim of the study was to quantify the activity as recorded by electromyography during ergometer cycling in eleven different muscles of the lower extremity. Eleven healthy subjects rode in twelve different ways at different work-load, pedalling rate, saddle height and pedal foot position. Vastus medialis and lateralis, gastrocnemius medialis and lateralis and the soleus muscle were the most activated muscles. Changes in muscle activity during different calibrations were studied in eight of the eleven muscles. An increase in work-load significantly increased the mean maximum activity in all the eight muscles investigated. An increase of the pedalling rate increased the activity in the gluteus maximus, gluteus medius, vastus medialis, medial hamstring, gastrocnemius medialis and soleus muscles. An increase of the saddle height increased the muscle activity in the gluteus medius, medial hamstring and gastrocnemius medialis muscles. Use of a posterior pedal foot position increased the activity in the gluteus medius and rectus femoris muscles, and decreased the activity in the soleus muscle.

Adult↗
PubMed1985

Patellar forces during knee extension.

A radiographical study of 20 loaded knees of healthy subjects and a knee dissection study of 20 specimens were performed in order to present a two-dimensional patello-femoral joint biomechanical model. A constant knee-extending moment gave 25-40% lower force magnitudes in the patellar tendon than in the quadriceps tendon if the knee was flexed to 60-120 deg. The magnitude of the patello-femoral joint compressive force reached its maximum at 90 deg knee angle and decreased slightly towards 120 deg. A compressive force between quadriceps tendon and femoral intercondylar groove was present above 60 deg knee angle and its magnitude was estimated. The patellar forces in women were about 20% higher than in men. The biomechanical model may be used in knee rehabilitation activities to optimize and individualize exercise programmes. The model may also be applied to daily activities in order to quantify patellar forces.

Biomechanical Phenomena↗
PubMed1984

Load on knee joint structures and muscular activity during lifting.

The load on the knee joints during lifting has been less studied than low back load. Healthy subjects lifted a 12.8-kg box from floor to table-level in three different ways; 1) with straight knees, 2) with bent knees and the box in front of the knees, and 3) with bent knees and the box between the knees. The loading moment of force about the bilateral knee axis was calculated by means of a computerized static sagittal plane model. Electromyography was recorded from quadriceps and ischiocrural muscles. The beginning of the flexed-knee lifts caused a flexing loading knee moment of about 50 Nm and a knee angle of 90 degrees. Straight-knee lifts gave all through the lift an extending loading moment. During the final phase of all lifts there was an extending loading knee moment of about 55 Nm and a knee angle of 0 degrees. The three lifts were compared and discussed from a biomechanical and ergonomical point of view.

Adult↗
PubMedDate not supplied

Tibiofemoral joint forces during ergometer cycling.

Six healthy subjects pedaled on a weight-braked bicycle ergometer at different workloads, pedaling rates, saddle heights, and pedal foot positions. The subjects were filmed with a cine-film camera and pedal reaction forces were recorded from a force transducer mounted on the left pedal. Net knee moments were calculated using a dynamic model, and the tibiofemoral shear and compressive force magnitudes were calculated using a biomechanical model of the knee. During cycling at 120 W, 60 rpm, midsaddle height, and anterior pedal foot position, the mean peak tibiofemoral compressive force was 812 N [1.2 times body weight (BW)]. The maximum anteriorly directed tibiofemoral shear force was found to be low (37 N). The compressive and shear forces were significantly increased by an increased ergometer workload. The pedaling rate had no influence on the tibiofemoral force magnitudes. The stress on the ACL was low and could be further decreased by use of the anterior foot position instead of the posterior.

Adult↗
PubMedDate not supplied

Tibiofemoral joint forces during isokinetic knee extension.

Using a Cybex II, eight healthy male subjects performed isokinetic knee extensions at two different speeds (30 and 180 deg/sec) and two different positions of the resistance pad (proximal and distal). A sagittal plane, biomechanical model was used for calculating the magnitude of the tibiofemoral joint compressive and shear forces. The magnitude of isokinetic knee extending moments was found to be significantly lower with the resistance pad placed proximally on the leg instead of distally. The tibiofemoral compressive force was of the same magnitude as the patellar tendon force, with a maximum of 6300 N or close to 9 times body weight (BW). The tibiofemoral shear force changed direction from being negative (tibia tends to move posteriorly in relation to femur) to a positive magnitude of about 700 N or close to 1 BW, indicating that high forces arise in the ACL when the knee is extended more than 60 degrees. The anteriorly directed shear force was lowered considerably by locating the resistance pad to a proximal position on the leg. This model may be used when it is desirable to control stress on the ACL, e.g., in the rehabilitative period after ACL repairs or reconstructions.

Adult↗