Biomedical subjects

M O Ericson

Publications and source records attributed to M O Ericson.

12 recordsLinked to original sources

PubMed1991

An electromyographic study of dental work.

Musculoskeletal disorders are common among dentists, and have been ascribed to the demands of high precision work and sustained static loading in the neck-shoulder region, combined with a flexed and rotated cervical spine. In order to determine muscular load levels during dentistry, activity in neck, shoulder, and arm muscles was recorded using an electromyography technique (EMG). Normalized mean, median, 10th and 90th percentile EMG amplitude levels (% maximal reference contraction, %max-RVC) were calculated during ordinary dental work. Among the muscles investigated, the trapezius muscle on both sides had the highest mean (the right trapezius 9.0% and the left 7.6% of max-RVC) and 10th percentile amplitude levels (both about 2% of max-RVC). The trapezius muscles showed similar myoelectric activity on the right and left side, probably because of similar muscular static load on the both sides. The right extensor carpi radialis muscle had a significantly higher muscular load level than the left one, possibly due to stabilization demands on the dominant wrist during demanding precision work. The infraspinatus muscle had low activity level on both sides, reflecting that the dentists worked with a small degree of arm elevation and external rotation. The dentistry work thus seems to generate relatively high muscular load on both trapezius and dominant extensor-carpi-radialis, and relatively low load on the infraspinatus muscle.

Adult↗

PubMed1988

Mechanical muscular power output and work during ergometer cycling at different work loads and speeds.

The aim of the study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling at different work loads and speeds. Six healthy subjects pedalled a weight-braked cycle ergometer at 0, 120 and 240 W at a constant speed of 60 rpm. The subjects also pedalled at 40, 60, 80 and 100 rpm against the same resistance, giving power outputs of 80, 120, 160 and 200 W respectively. The subjects were filmed with a cine-film camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work for the hip, knee and ankle joint muscles was calculated using a model based upon dynamic mechanics and described elsewhere. The total work during one pedal revolution significantly increased with increased work load but did not increase with increased pedalling rate at the same braking force. The relative proportions of total positive work at the hip, knee and ankle joints were also calculated. Hip and ankle extension work proportionally decreased with increased work load. Pedalling rate did not change the relative proportion of total work at the different joints.

Adult↗

PubMed1988

Efficiency of pedal forces during ergometer cycling.

The aim of this study was to record the forces applied to the pedal during ergometer cycling and to calculate the effectiveness of these force vectors. Six healthy subjects rode a weight-braked bicycle ergometer at different work loads, pedaling rates, saddle heights, and pedal foot positions. The left lower limb and crank motions were recorded by a cinefilm camera and pedal reaction forces by a Kistler force measuring transducer mounted on the left pedal. The force effectiveness was computed as a ratio between the force tangential to instantaneous direction of pedal movement and the resultant force. The mean force efficiency ratio significantly increased by an increase of the ergometer work load or use of the anterior foot position instead of the posterior. It was not significantly changed due to alterations of the pedaling rate or saddle height.

Adult↗

PubMed1988

Muscular function during ergometer cycling.

Quantified EMG and calculated mechanical muscular power output data were combined to provide further analysis of muscular function during ergometer cycling. The single-joint muscles; gluteus maximus, gluteus medius, vastus medialis, vastus lateralis and soleus all showed a more predictable function with approximately linear relationship between calculated power output and recorded EMG. The function for the two-joint muscles was found to be more complex. Biceps femoris seemed to act mainly as a hip extensor and medial hamstring mainly as a knee flexor. Gastrocnemius medialis was proposed to act more as a plantar flexor and gastrocnemius lateralis as a knee flexor.

Adult↗

PubMed1987

Patellofemoral joint forces during ergometric cycling.

We estimated the patellofemoral joint forces generated during pedaling on a bicycle ergometer. Our calculations were based on measurements from a force transducer mounted on the pedal, 16-mm cine-film sequences, and biomechanical models of the cycling motion and of the patellofemoral joint. Six healthy male subjects cycled at different work loads, pedaling rates, saddle heights, and pedal foot positions. The maximum patellofemoral compressive force was 905 N (1.3 times body weight [BW]) when cycling with an anterior foot position at 120 W, 60 rpm, and middle saddle height. The mean peak compressive force between the quadriceps tendon and the intercondylar groove was 295 N (0.4 BW), and the patellar-tendon and quadriceps-tendon strain forces were 661 N (0.9 BW) and 938 N (1.3 BW), respectively. The patellofemoral joint forces were increased with increased work load or decreased saddle height. Different pedaling rates or foot positions did not significantly change these forces.

Adult↗

PubMed1986

Power output and work in different muscle groups during ergometer cycling.

The aim of this study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at 120 watts (W) and 60 revolutions per minute (rpm). The subjects were filmed with a cine camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work at the hip, knee and ankle joint was calculated using a model based upon dynamic mechanics described elsewhere. The mean peak concentric power output was, for the hip extensors, 74.4 W, hip flexors, 18.0 W, knee extensors, 110.1 W, knee flexors, 30.0 W and ankle plantar flexors, 59.4 W. At the ankle joint, energy absorption through eccentric plantar flexor action was observed, with a mean peak power of 11.4 W and negative work of 3.4 J for each limb and complete pedal revolution. The energy production relationships between the different major muscle groups were computed and the contributions to the total positive work were: hip extensors, 27%; hip flexors, 4%; knee extensors, 39%; knee flexors, 10%; and ankle plantar flexors 20%.

Adult↗

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

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↗

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↗