Biomedical subjects

D J Newham

Publications and source records attributed to D J Newham.

49 records · Page 3Linked to original sources

PubMed1986

Plasma creatine kinase changes after eccentric and concentric contractions.

This study was undertaken to determine whether the large delayed creatine kinase (CK) rise, previously only reported in normal subjects after stepping exercise, was caused by the eccentric or concentric contractions. On separate occasions, five normal subjects performed the same amount of total work by walking either up (mainly concentric contractions) or down (mainly eccentric contractions) a treadmill inclined at 13 degrees. After uphill walking, peak plasma CK values of 60-200 IU/liter occurred 24 hours after exercise. Downhill walking resulted in peak values of 700-1500 IU/liter 4-7 days later. It is concluded that it is the eccentric contractions that are responsible for the large enzyme efflux.

Adult↗

PubMed1986

Skeletal muscle damage: a study of isotope uptake, enzyme efflux and pain after stepping.

We have studied the occurrence of skeletal muscle uptake of 99mtechnetium pyrophosphate (Tc-PYP), creatine kinase (CK) release and muscle pain in normal subjects after exercise. Five subjects stepped on and off a high bench in such a way that one leg stepped up and the other down. Pain only developed in the muscles used for descending: quadriceps, adductors and gluteal muscles of one leg and the calf muscle of the other. A large rise in plasma CK occurred in four subjects but no increased Tc-PYP muscle uptake was seen in the quadriceps. In the four subjects with high CK effluxes, increased isotope uptake was seen in the thigh adductors used when stepping down; in the two subjects with the largest CK effluxes there was extensive uptake into the gluteal muscles. Muscle pain preceded and was not well correlated with either the magnitude of the enzyme release or the amount and distribution of increased muscle isotope uptake. We conclude that delayed onset muscle pain, the cause of which remains unknown, is a poor indicator of muscle damage as indicated by circulating muscle enzymes and muscle isotope uptake. Tc-PYP uptake by skeletal muscle can provide useful information about the localisation and time course of muscle damage.

Adult↗

PubMed1986

Contractile properties of the adductor pollicis in obese patients on a hypocaloric diet for two weeks.

The muscle function of 21 obese patients on a hypocaloric diet (450 kcal/day) was studied. On days 1, 7, and 12 the maximal isometric force and contractile properties (force:frequency relationship, relaxation rate, and fatigability) of the adductor pollicis were measured. The patients lost a mean of 5.7 kg but there was no significant change in the muscle strength or contractile properties. Twenty normal and three malnourished patients were also studied; the latter demonstrated abnormalities of muscle function. The use of such tests to monitor changes in nutritional status must be treated with caution.

Adult↗

PubMed1986

Experimental human muscle damage: morphological changes in relation to other indices of damage.

The effects of eccentric exercise have been examined in human calf and biceps muscles. Release of muscle creatine kinase and uptake of technetium pyrophosphate have been followed for up to 20 days after the exercise and the results are related to the morphological changes seen in needle biopsy samples. The response to exercise was variable, all subjects developing pain and tenderness in the exercised muscles after 1-2 days and this was followed, in most subjects, by a large increase in plasma creatine kinase 4-6 days after the exercise. This was paralleled by an increased uptake of technetium pyrophosphate into the exercised muscle. Biopsies of the affected muscles showed little or no change in the first 7 days after the exercise but later degenerating fibres were seen, as well as infiltration by mononuclear cells and eventually, by 20 days, signs of regeneration. Very extensive changes were seen in the calf muscle of one subject; changes in the biceps were qualitatively similar but not so severe. In the severely affected calf muscle type II fibres were preferentially damaged. Mononuclear cell infiltration both between and within degenerating fibres was maximal well after the time of peak plasma creatine kinase and it is likely that in eccentrically exercised muscle infiltrating mononuclear cells act to scavenge cellular debris rather than to cause damage to the muscle.

Adult↗

PubMed1986

Clinical and experimental application of the percutaneous twitch superimposition technique for the study of human muscle activation.

The use of percutaneous stimulation for twitch superimposition in the human quadriceps has been compared with stimulation via the femoral nerve. It was found that the relationship between the extra force generated by the twitch and the level of voluntary contraction was independent of the percentage of the muscle stimulated. The technique was used to study activation of the quadriceps and biceps in a group of young healthy adults, and quadriceps activation in patients with musculo-skeletal disorders. The majority of subjects could fully activate their muscles during brief isometric contractions. Inhibition was demonstrated in patients with muscle pain and joint pathology and in subjects with a previous history of knee or joint injury. The technique is easy to use and provides a simple way of detecting inhibition where it might not be anticipated, such as in the absence of pain. Where inhibition is demonstrated the technique can be used to predict approximately the maximum force available.

Adolescent↗

PubMed1984

Role of mechanical damage in pathogenesis of proximal myopathy in man.

No adequate explanation has as yet been provided for the predominant proximal and symmetrical distribution of skeletal muscle weakness and wasting in human myopathies. One obvious difference between proximal and distal muscles is that in their postural antigravity role the former are involved in eccentric contractions to a much greater extent than are the latter. Recent physiological studies have shown that eccentric contractions produce considerable muscle damage in normal healthy subjects. The damage starts in individual sarcomeres but becomes more extensive over 1-2 days, the progression probably being due to the stronger sarcomeres stretching the weaker, damaged sarcomeres during normal activity and/or to the enzyme degradation of myofibrillar proteins when muscle damage results in Ca++ inflow. As a muscle becomes weaker and unable to meet the functional demands made upon it the likelihood of accidental stretch becomes greater. The vicious circle of weakness, stretch, damage, and further weakness may be the reason why the proximal muscles, which normally function eccentrically to some degree, are the most severely affected in a wide range of myopathic disorders.

Biomechanical Phenomena↗

PubMed1983

Carbonic anhydrase III in Duchenne muscular dystrophy.

Plasma carbonic anhydrase III (CAIII) levels determined by radioimmunoassay have been compared, in detail, with creatine kinase (CK) as indices of Duchenne muscular dystrophy (DMD). CAIII levels were markedly elevated in all patients but variability of levels in a number of individual patients was higher than CK.

Adolescent↗

PubMed1983

Large delayed plasma creatine kinase changes after stepping exercise.

Muscle changes have been examined in 16 normal subjects (eight female) after both a 20-minute and a prolonged step test. Stepping differs from most exercise tests in that it involves eccentric contractions (negative work) in which the active muscle is lengthened. Plasma creatine kinase (CK), muscle force, contractile properties, and tenderness in the quadriceps were measured for up to 9 days after the exercise. Muscle tenderness was experienced only in the muscles that had performed eccentric contractions (i.e., stepped down). All subjects showed some early rise in CK (less than 400 IU/liter) but eight (both male and female) showed a much greater response (up to 34,500 IU/liter) which took a long time to reach peak levels (4-5 days after stepping). It is suggested that eccentric contractions involved in this form of exercise result in some particular form of muscle damage which, in susceptible subjects, may initiate changes giving rise to a large delayed release of muscle enzymes.

Adult↗

PubMed1983

Ultrastructural changes after concentric and eccentric contractions of human muscle.

Four normal subjects performed a 20 min step test using a step of the same relative height. During the test the quadriceps muscle of one leg contracted concentrically throughout by stepping up, while the contralateral muscle contracted eccentrically by controlling the step down. Thus both muscles performed the same amount of work. Three subjects had bilateral needle biopsies just prior to exercise. All four had bilateral biopsies immediately after exercise, and 24-48 hours later when the muscles which had contracted eccentrically were painful. The samples were examined by light and electron microscopy. No abnormalities were seen in pre-exercise samples nor after exercise in muscles which had contracted concentrically. The muscles which had contracted eccentrically showed some damage immediately after exercise. In the samples taken 24-48 hours after exercise the damage was more marked and involved a greater percentage of fibres. In view of the known differences between these types of contractions it is suggested that the initial damage is mechanically induced. The exacerbation of damage with time could be due to mechanical or chemical factors.

Adult↗

PubMed1983

Pain and fatigue after concentric and eccentric muscle contractions.

1. Normal subjects performed a step test in which the quadriceps of one leg contracted concentrically while the contralateral muscle contracted eccentrically. 2. Maximal voluntary force and the force: frequency relationship were altered bilaterally as a result of the exercise, the changes being greater in the muscle which had contracted eccentrically. Recovery occurred over 24 h. 3. Electromyographic studies using three sites on each muscle showed an increase in electrical activation during the exercise only in the muscle which was contracting eccentrically. Recovery followed a time course similar to that of the contractile properties. 4. Pain and tenderness developed only in the muscle which had contracted eccentrically. Pain was first noted approximately 8 h after exercise and was maximal at approximately 48 h after exercise, at which time force generation and electrical activation had returned to pre-exercise values. 5. Eccentric contractions cause more profound changes in some aspects of muscle function than concentric contractions. These changes cannot be explained in simple metabolic terms, and it is suggested that they are the result of mechanical trauma caused by the high tension generated in relatively few active fibres during eccentric contractions.

Adult↗

PubMed1982

Force, contraction frequency and energy metabolism as determinants of ischaemic muscle pain.

Ischaemic muscle pain was studied in a total of 78 experiments on 3 normal subjects. The development of pain induced by intermittent voluntary isometric contractions was recorded whilst force and frequency of contraction were varied. As the muscle progressively expends energy, pain (P) develops in an exponential fashion and can be expressed by the function P = (F x t)k/C where (F x t) is the integral of force with time, k, an exponent, and C, a constant. The exponent is fairly constant despite changes in frequency. The time of pain onset and energy expenditure at the point of intolerable pain depend on frequency. At a given frequency, energy expenditure at intolerable pain is independent of the force of contraction.

Energy Metabolism↗

PubMed1982

Severe muscle cramps relieved by transcutaneous nerve stimulation: a case report.

The case is described of a 51-year-old man with a 21 year history of severe, long-lasting and widespread muscle cramps. Physical examination revealed muscle hypertrophy and fasciculation; electromyography showed spontaneously active motor units which disappeared during sleep. Cramps could be aborted by ice or mechanical vibration but the most effective management was achieved using transcutaenous nerve stimulation.

Biopsy, Needle↗

PubMedDate not supplied

The human force:velocity relationship; activity in the knee flexor and extensor muscles before and after eccentric practice.

The human voluntary force:velocity relationship frequently fails to demonstrate the expected high eccentric forces. Possible explanations include unique activation strategies which might be affected by neural learning mechanisms. We investigated the effect of practicing eccentric contractions on (1) the force:velocity relationship of the human knee extensor muscles and (2) the extent of agonist and antagonist muscle activity. Eight healthy adults [seven women, group mean age 31 (SEM 5) years +/-] practiced twice a week for 4 weeks using their non-dominant legs. Each session comprised three isokinetic concentric and eccentric maximal voluntary contractions (MVC) at randomised angular velocities of 100, 200 and 300 degrees.s-1. Before and after, the force:velocity relationship was determined bilaterally (angular velocities 0-300 degrees.s-1). There were no significant differences in the forces generated or relative electromyogram (EMG) activity after practice, although there was a trend for dynamic forces to increase. Beforehand, the bilateral eccentric MVC forces were lower than isometric (P < 0.0025); afterwards they were broadly similar. The agonist EMG was similar during isometric and eccentric contractions, but lower during concentric (P < 0.03). Antagonist EMG activity showed considerable individual variation, was similar during all contraction types and tended to be greater during dynamic contractions. These data indicate that neither central learning mechanisms nor total muscle activation strategies underlie the human failure to produce the expected high eccentric voluntary forces in humans.

Adult↗