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Biomedical subjects

B Gerdle

Publications and source records attributed to B Gerdle.

67 records · Page 4Linked to original sources
PubMed1988

Do the fibre-type proportion and the angular velocity influence the mean power frequency of the electromyogram?

The dependence of the mean-power frequency and the signal amplitude of the electromyogram (EMG) on the angular velocity and the fiber-type proportion were investigated in nine female volunteers. The subjects were required to perform maximum knee extensions using an isokinetic dynamometer at different angular velocities; 0.57, 1.05, 1.57, 2.09 and 3.14 rad s-1. Electromyographic signals were obtained from the vastus lateralis, vastus medialis and the rectus femoris muscles. The angle and the torque signals were recorded simultaneously with the three EMG signals on a tape-recorder. From the EMG recordings the mean power frequency (MPF) and the signal amplitude were determined. Muscle biopsies were later obtained from the right vastus lateralis and stained for alkaline and acid mATPase for the determination of fibre-type proportions and areas. Neither the signal amplitude nor the MPF of the EMG of the three muscles were dependent on the angular velocity. The MPF of the vastus lateralis correlated significantly (r = -0.93) with the type 1 fibre proportion at 1.57 rad s-1. However, there was no significant correlation between the areas of the fibre types, alone or together, and the MPF. In conclusion the fibre-type proportion was the major factor behind the MPF irrespective of angular velocity.

Adenosine Triphosphatases↗
PubMed1988

Rank order of peak amplitude of EMG between the three muscles of triceps surae during maximum isokinetic contractions.

Peak torque (PT) of maximum isokinetic plantar flexions was measured at 4 angular velocities (30, 60, 120 and 180 degrees/s) in 88 subjects. Simultaneous recordings of electromyograms (low-pass filtered and rectified) were obtained from the three heads of m. triceps surae. Subjects were clinically healthy subjects randomly chosen in age-groups 40-44, 50-54 and 60-64 years. The delays (in degrees) in range of motion (from maximum dorsiflexed position) of PT and of peak value of the low-pass filtered EMG-amplitudes (pEMG) were determined and ranked. pEMG of gastrocnemius medialis was reached before m. gastrocnemius lateralis which reached pEMG before m. soleus. At 30 degrees/s PT coincided with the pEMG of m. soleus, while at 120 and 180 degrees/s PT coincided with pEMGs of mm. gastrocnemii. The fixed rank order of pEMGs in the three muscles might be a reflexion of differences in the motor unit populations in the mm. gastrocnemii and m. soleus. The findings indicate that the relative roles of the three muscles, when torque-production is concerned, is dependent on angular velocity.

Adult↗
PubMed1987

Repeated isokinetic plantar flexions at different angular velocities.

Peak torque (PT), contraction work (CW) and mean power (CP) were measured for each of 200 repetitive isokinetic (maximum effort) plantar flexions. Simultaneous recording of integrated electromyograms (iEMG) were obtained from the three parts of the triceps surae muscle. Four tests at different angular velocities (30, 60, 120 and 180 degrees s-1 (degrees X s-1] were performed with at least 2 weeks between each test. The subjects were eight clinically healthy females (24-36 years). At all four angular velocities CW, CP and PT decreased steeply during the first approximately 70 contractions, followed by a steady-state level with no further significant decreases. The relative decreases of PT and CP were significantly smaller than for CW at all velocities. The relative CW decline increased with angular velocity; the relative PT and CP decreases were not velocity dependent. Also iEMG activity decreased in two phases during the 200 contractions and were on a significantly lower relative level at 180 degrees X s-1. However the reduction of range of motion was significantly greater at 180 degrees X s-1 and when the iEMG activity was compensated for this decrease the relative decreases in electromyographic activity were similar at the four angular velocities. The results indicated that CW was more sensitive to fatigue than PT and CP and that CW fatigue was dependent on angular velocity.

Adult↗
PubMed1987

Mean power frequency and integrated electromyogram of repeated isokinetic plantar flexions.

Peak torque (PT), contraction work (CW), mean power (CP), and time for contraction (t) were recorded for each of 200 full range-of-motion repetitive isokinetic (maximum effort) plantar flexions at the preset angular velocity 60 degrees s-1 (degrees X s-1). The subjects were 12 healthy males (42-46 years). Simultaneous recordings of electromyographic activity of the three parts of the triceps surae muscle were made. The electromyograms were truly integrated and the mean power frequency was also calculated for each of the contractions. The mechanical variables decreased steeply during approximately the first 70 contractions (the fatigue phase) followed by a steady-state level (the endurance level) with no further significant decrease. The fatigue phase was composed of two parts. The first was characterized by decreases in CW, MPF and in the ratio CW/iEMG, while iEMG and iEMG/t were unaltered. During the second part decreases in iEMG and iEMG/t occurred while MPF and CW/iEMG had stabilized. During the endurance level all the variables were stable but lowered when compared with the initial contractions of the fatigue phase. The results indicated that the mechanical fatigue went through two parts before the steady-state level was established.

Adult↗
PubMed1987

Fatigue and endurance of lower extremity muscles in relation to running velocity at OBLA in male orienteers.

At three occasions during a year, the ratio of contractional work (output)/integrated electromyographic activity (input), that is, CW/iEMG, was measured during repetitive maximum isokinetic manoeuvres for m. quadriceps and m. triceps surae in male elite orienteers. Running velocity at the onset of blood lactate accumulation (VOBLA), which was considered as a measure of running performance, and maximal oxygen uptake (VO2max) were analysed at each test. Type and amount of training were continuously registered. For m. quadriceps there was a decline in CW/iEMG during the first 30 manoeuvres, followed by an unchanged plateau level. In contrast, m. triceps surae showed a plateau level of virtually unaltered CW/iEMG ratio from the start to the end of the experiment. The differences might be explained by structural causes, but also by local muscle adaptation to training. The plateau level of CW/iEMG of m. quadriceps was positively correlated to VO2max. An increase in the plateau level of CW/iEMG was found for both tested muscle groups after the winter training period (mainly low intensity road running) when both VOBLA and VO2OBLA increased. During the competition period (mainly high intensity forest running), the whole group increased while some orienteers lowered their VOBLA. During this period, no changes in the plateau level of CW/iEMG of any muscle group or in VO2OBLA occurred. The changes in the plateau level of CW/iEMG might express local muscle adaptations to changes in running technique and aerobic/anaerobic demands during low intensity road running versus high intensity forest running.

Adult↗
PubMed1986

Prediction of peak torque and contraction work at different isokinetic angular velocities of plantarflexion.

Contraction work (CW) and peak torque (PT) of maximum isokinetic plantar flexions were measured in clinically healthy subjects randomly chosen from the official census list of Umeå, Sweden, in three groups: 40-44, 50-54 and 60-64 years of age, with similar proportions of men and women. Maximum isokinetic plantar-flexions were performed at angular velocities of 30, 60, 120 and 180 degrees X s-1. Body-weight, height and crural circumference were measured. Subjects rated their levels of leisure and occupational activities. To establish formulae to predict CW and PT, stepwise regression procedures were applied. The predictive powers (r2) of the formulae which incorporated age, sex and crural circumference, were higher for PT (30 degrees X s-1: 0.82, 60 degrees X s-1: 0.79, 120 degrees X s-1: 0.75, 180 degrees X s-1: 0.56) than for CW (30 degrees s-1: 0.63, 60 degrees s-1: 0.63, 120 degrees s-1: 0.60, 180 degrees s-1: 0.52). Thus the part of the variance explained decreased with increasing angular velocity, but more than 50% was still explained at 180 degrees s-1. The results indicate that the mechanical output of the plantar flexors is predictable.

Adolescent↗
PubMed1986

Isokinetic strength and endurance in peripheral arterial insufficiency with intermittent claudication.

Isokinetic plantar flexor peak torques (PT) and contractional work (CW) of the triceps surae muscle have been measured in 24 patients with peripheral arterial insufficiency and intermittent claudication and in 15 controls. Tests were performed both during non-fatiguing (30-180 degrees/s) and fatiguing (200 repeated plantar flexions at 60 degrees/s) conditions. The electromyographic signals (iEMG) from all three heads of the triceps surae were measured. The patients were significantly weaker (PT) and produced significantly less contractional work (CW) than the controls. In contrast, similar iEMGs of the triceps surae heads indicated similar levels of activation. At 40 contractions the majority of the patients had already given up and the remainder showed significantly greater declines in PT (50%) and CW (55%) than did the controls (13% and 18%, respectively). The decline in muscular excitations was similar in both groups. The ratio CW/iEMG showed a dramatic decline in the patients but was virtually constant in the controls. These results indicate a fatigue of low-frequency type in the patient group. There were close correlations between maximum walking tolerance and total work production.

Aged↗
PubMed1985

Mechanical output and iEMG of isokinetic plantar flexion in 40-64-year-old subjects.

Peak torque (PT), contractional work (CW) and mean power of isokinetic plantar flexions were measured in unselected, clinically healthy subjects, randomly chosen from the official census lists of Umeå, in three age groups: 40-44, 50-54 and 60-64 years. Simultaneous recordings of integrated electromyograms (iEMG) were obtained by surface electrodes from all three heads of the m. triceps surae. PT and CW decreased exponentially with increasing velocity of angular motion and at 60 degrees X s-1 (r2 = 0.79 and 0.63, respectively) were adequately determined by crural circumference, age and sex. The muscular output declined with increasing age. Both output and iEMG showed an approximate 3:2 male:female ratio. Therefore, the ratio CW/iEMG was age, but not sex-dependent at any given velocity of angular motion. Independently of this age, the iEMGs were inversely proportional to velocity of angular motion, while iEMG/manoeuvre time was constant indicating that torque/velocity and work/velocity exponential relationships are mainly determined by muscular properties. Based on the literature it is suggested that the dependence of the measured parameters on age and sex is determined by muscular properties, rather than by the central nervous system. Moreover, the CW/iEMG ratio appears to provide a comprehensive picture of excitation and mechanical output of the muscle group studied and may therefore be a useful measure.

Adult↗
PubMed1985

Characteristics of repeated isokinetic plantar flexions in middle-aged and elderly subjects with special regard to muscular work.

Contractional work (CW), mean power (CP) and peak torque (PT) were recorded for each of up to 200 full range-of-motion (RoM) repetitive isokinetic (60 degrees X s-1) maximum effort plantar flexions. Subjects were 88 unselected clinically healthy males and females aged 40-44, 50-54 and 60-64 years with similar distributions of age and sex. Simultaneous recordings of integrated electromyograms (iEMGs) were obtained from the three heads of the m. triceps surae. Within approximately 50 contractions CW had decreased 36-21% for the different groups (by age and sex). The corresponding decreases for PT and CP were 28-14% and 25-13%, respectively. During the remaining part of the experiment only minor changes occurred. For CW but not for PT and CP reductions were negatively related to age while no sex differences were evident. Decreases in CW were significantly smaller in subjects physically active during leisure time than in those relatively inactive. Decreases in active range-of-motion provide an explanation for greater reductions in CW than in PT and CP. The iEMGs of the mm. gastrocnemii decreased significantly more than that of the m. soleus. Close associations between CW and iEMG were evident. Hence the chosen expression of output/input balance: CW/iEMG was nearly constant throughout the experiments. Results indicate that measurements of contractional work throughout the range-of-motion may provide more differentiated information on mechanical output during supposedly fatiguing dynamic manoeuvres than can recordings of maximum strength.

Adult↗
PubMed1985

Isokinetic plantar flexion endurance. Reliability and validity of output/excitation measurements.

The reliability and validity of isokinetic measurement of plantar flexion endurance has been studied by a method previously described by us which utilizes simultaneous measurements of mechanical contractional work (CW) and integrated electromyogram (iEMG). The reliability was gauged by test/re-test with a two year's interval; while validity was assessed by myoelectric power spectrum analyses. The output/input balance (CW/iEMG) remained unchanged for the group as well as inter-individually. Changes in myoelectric power spectrum as function of number of contractions were clearly indicative of fatigue. Under the present conditions fatigue of fast twitch motor units may explain the rapid decreases in output and excitation followed by nearly steady state levels of all registered parameters. As is the case for non-fatigued isokinetic plantar flexions, the motor unit recruitment order appears quite stereotyped during plantar flexion fatigue. The findings of significantly lower mean power spectrum during the first part of each contraction than during the second part may support the size-principle described by Henneman.

Adult↗
PubMedDate not supplied

Survival with pain: an eight-year follow-up of war-wounded refugees.

The aim of this study was to investigate the nature of chronic pain in male war-wounded refugees and to examine the relationship between chronic pain and psychiatric symptoms. A culturally heterogeneous group of 44 war-wounded refugees were investigated during hospitalization, shortly after arrival, and followed up after two years. This study is an additional follow-up after eight years. The data collection methods used were structured interviews and physical examination. The measures of outcome were: Visual Analogue Scale (VAS) grading of pain; clinical categorization of pain into nociceptive or neurogenic; Hopkins Symptom Check List (HSCL-25); Post Traumatic Symptom Scale (PTSS-10). Chronic pain was found in 32 (73%) out of 44 subjects. The pain was purely nociceptive and neurogenic in 53% and 25%, respectively. The frequency of psychiatric symptoms was significantly related to the mean intensity of pain. War-wounded refugees display psychiatric symptoms and chronic pain in a complex pattern. Further research is needed as a basis for pain rehabilitation programmes suitable for this group.

Adult↗