Search PubMed⌕ Search

Biomedical subjects

D J Newham

Publications and source records attributed to D J Newham.

At least 19 recordsLinked to original sources
PubMed2001

Knee muscle isometric strength, voluntary activation and antagonist co-contraction in the first six months after stroke.

PURPOSE: Muscle weakness may contribute to functional problems after stroke, but is rarely addressed during rehabilitation. Functional problems are commonly thought to be caused by abnormal movement patterns or possibly disuse atrophy. We investigated voluntary isometric strength, activation and the extent of co-contraction in the knee muscles during the first six months during stroke. METHODS: Twelve stroke patients (58 +/- 3 years, mean+/- SEM, 7 female) were studied bilaterally on admission for rehabilitation (21 +/- 1 days after stroke) and then at 1, 2, 3, and 6 months. Twenty healthy controls (61 +/- 5 years, 17 female) were tested once on their preferred leg. Subjects performed maximal voluntary contractions of the quadriceps and hamstring muscles. Simultaneous measurements were made of agonist force and surface EMG from agonist and antagonist muscles. Voluntary activation was estimated using the twitch superimposition technique. RESULTS: Both paretic muscles showed lower (p = 0.01-0.0005) voluntary strength than both non-paretic and control muscles until three months after stroke. Co-contraction of antagonists was similar in all groups and greater during knee extension than flexion. Stroke patients showed considerable bilateral voluntary activation failure (25-40%, p = 0.01-0.001) throughout the study while most control subjects did not (group mean 7%). CONCLUSIONS: The muscle weakness and bilateral activation failure in the stroke patients was not explained by either excessive antagonist activity or disuse atrophy. They had potential for increased voluntary strength and if this were addressed during rehabilitation, then the rate and extent of functional recovery might be enhanced.

Case-Control Studies↗
PubMed2000

Influence of muscle temperature during fatiguing work with the first dorsal interosseous muscle in man: a 31P-NMR spectroscopy study.

Six healthy subjects rapidly lifted and lowered a small (250 g) weight with the first dorsal interosseous muscle (FDI) of one hand while the work performed was recorded continuously until fatigue (defined as losing the ability to continue lifting). Work was recorded in units of chart recorder trace displacement from baseline (centimeters) as an isotonic transducer followed the movement of the weight. In all experiments, the temperature of the hand was first adjusted by immersion in a controlled-temperature water bath. In the warmest condition, the skin surface temperature over the FDI was 30.5(0.30) degrees C [mean (SE)]. After moderate cooling, this surface temperature was 21.5(0.16) degrees C. Cooling significantly reduced the time taken to reach fatigue and more than halved the work capacity. An intermediate degree of cooling was also used in four subjects, showing that most of the effects seen were changing incrementally. Before work, and at fatigue, intracellular metabolic conditions in the FDI were studied by phosphorus nuclear magnetic resonance (31P-NMR) spectroscopy, with occlusion of the blood flow maintained during measurements. The mean intracellular pH of the FDI was also calculated. The changes observed were all consistent with the fact that intense work requires energy which must be derived largely from intracellular stores of phosphocreatine and glycogen. Less work made less demand upon reserves, and created lower concentrations of waste products and by-products. The observations did not, however, allow us to explain why fatigue occurred at a particular point or why work capacity was reduced by cooling.

Adult↗
PubMed1999

Inter-rater reliability of postural observation after stroke.

OBJECTIVE: To explore the inter-observer reliability of bedside observations of stroke patients' posture using two versions of a pictorial tool. DESIGN: Three projects were conducted. The initial version of the tool was used in project 1. The modified version was used in projects 2 and 3. In each project a pair of observers (comprising the main observer and one of five co-observers with varying degrees of experience in observing posture) used the tool to make simultaneous observations of 19 aspects of the posture of a sample of stroke patients. Each patient was observed in one or more of four positions (seated, supine and lying on the affected and unaffected side). The degree of inter-observer agreement was sought by calculating kappa values and percentage agreement. SETTING: Medical wards, care of the elderly wards and a stroke unit. SUBJECTS: A convenience sample of 57 stroke patients. RESULTS: Four hundred and forty paired sets of observations were made (200 in project 1, 140 in project 2 and 100 in project 3). The main observer was in every pair. The co-observers made between 50 and 135 sets of observations each. When the results from all three projects were amassed, acceptable percentage agreement (i.e. > or =70%) was obtained for 67% (n = 78) and 73% (n = 55) of the results collected on aspects of the posture of the affected upper and lower limbs respectively. In contrast, acceptable percentage agreement for observations relating to the head, neck and trunk was obtained for only 34% (n = 50) of the results collected. Uneven distributions in the data made kappa values difficult to interpret. Inter-observer agreement was not noticeably higher for pairs in which both observers had prior experience of observing posture after stroke than for pairs in which one observer was relatively inexperienced. CONCLUSIONS: The tool has potential as a quick and simple means of collecting information at the bedside about stroke patients' posture. Refinements, additional training in using the tool for observers and further testing are suggested before its wider use is advocated.

Adult↗
PubMed1998

Structural and functional changes in skeletal muscle in anorexia nervosa.

Protein-energy malnutrition in anorexia nervosa is an under-recognised cause of muscle dysfunction. To characterise the skeletal myopathy that occurs in patients with severe anorexia nervosa, muscle function and structure were comprehensively examined in eight young adult female patients with severe (40%) self-induced weight loss. All of the patients showed impaired muscle function on strength and exercise measurement. The maximum voluntary contraction force for the patient group was significantly less than predicted values. Electromyography revealed myopathy in five of the patients, four of whom also had electro-physiological evidence of neuropathy. However, muscle biopsy specimens consistently showed myopathic changes with severe type 2 fibre atrophy but with no evidence of neuropathic changes. Ultrastructurally, there was separation and segmental loss of myofibrils and most biopsy samples contained abundant glycogen granules; we have previously reported that one of the most consistent biochemical abnormalities in these patients is impaired ischaemic lactate responses to forearm exercise. The result of severe protein-energy malnutrition on the musculo-skeletal system is a metabolic myopathy. Although the patients admitted to a variety of abnormal dieting behaviours, such as over-exercising and self-induced vomiting, no association was found between any of these and quantitative histological changes in the muscle biopsy samples. It is recommended that myopathy in anorexia nervosa be treated by instituting an appropriate refeeding programme.

Adult↗
PubMed1998

Quadriceps function, proprioceptive acuity and functional performance in healthy young, middle-aged and elderly subjects.

BACKGROUND: Muscle functions to generate force-producing movement and also has a role in proprioception. If ageing compromises these sensorimotor functions of muscle, the ability of older subjects to detect and correct postural sway may be impeded, resulting in impairment of functional performance. METHOD: To see if age-related changes occurred and, if so, what their effects might be. Quadriceps strength, proprioception, postural stability and functional performance were assessed in young (n = 20, mean age 23 years), middle-aged (n = 10, mean age 56 years) and elderly (n = 15, mean age 72 years) subjects. RESULTS: With increasing age there were decreases in quadriceps strength (r = -0.511; P < 0.001), acuity of joint position sense (r = -0.603; P < 0.001) and postural stability (ANOVA < 0.002) during stance conditions which placed a greater reliance on muscle proprioceptors. These changes may decrease postural stability confidence, resulting in impaired performance of common activities of daily living (r = 0.635; P < 0.001). CONCLUSIONS: The age-related deterioration in sensorimotor function of muscle may contribute to the increased fear and frequency of falls in elderly subjects, thereby decreasing independence.

Accidental Falls↗
PubMed1998

Positioning of stroke patients: evaluation of a teaching intervention with nurses.

BACKGROUND AND PURPOSE: There is agreement, although little evidence, that consistently positioning stroke patients in allegedly reflex-inhibiting positions is therapeutic and will enhance functional recovery. The nursing staff, therefore, needs to know and implement these postures and understand their potential underlying value. We examined nurses' knowledge of and practice in positioning stroke patients before and after a formal teaching intervention. METHODS: In a quasi-experimental study, 38 stroke patients and 59 nursing staff members (44 trained nurses and 15 healthcare assistants) from 6 wards were studied. The wards were randomly allocated to experimental or control status. Patients were assessed on entry into the study by use of a range of measures to establish group equivalence. Nineteen aspects of their position were documented at intervals throughout their stay with a previously developed observational tool. One thousand sets of observations of patient position were made. Using 2 questionnaires, the nurses' knowledge of the terminology used to denote posture and of issues relating to the moving and positioning of stroke patients was assessed before, immediately after, and 3 months after a package of formal teaching was implemented on the experimental wards. Nurse knowledge and patient position were used as the main outcome measures. RESULTS: Immediately after teaching, nurses in the experimental group scored significantly higher than those in the control group on the terminology questionnaire (P < 0.05) and the moving and positioning questionnaire (P < 0.001). Three months later, the experimental group scored higher on the latter questionnaire only (P < 0.005). The positioning of patients in the experimental group was improved overall after the teaching (P < 0.0005), and improvements to specific parts of the body were noted. CONCLUSIONS: It was possible to effect a degree of change in the nurses' knowledge of and practice in the positioning of stroke patients. However, the quality of patient positioning remained variable. More effective ways of improving positioning need to be developed. Only then can the effects of recommended positioning be evaluated.

Aged↗
PubMed1997

Sensorimotor changes and functional performance in patients with knee osteoarthritis.

OBJECTIVE: Muscles are essential components of our sensorimotor system that help maintain balance and perform a smooth gait, but it is unclear whether arthritic damage adversely affects muscle sensorimotor function. Quadriceps sensorimotor function in patients with knee osteoarthritis (OA) was investigated, and whether these changes were associated with impairment of functional performance. METHODS: Quadriceps strength, voluntary activation, and proprioceptive acuity (joint position sense acuity) were assessed in 103 patients with knee OA and compared with 25 healthy control subjects. In addition, their postural stability, objective functional performance (the aggregate time for four activities of daily living), and disabilities (lequesne index) were also investigated. RESULTS: Compared with the control subjects, the patients with knee OA had weaker quadriceps (differences between group mean 100N, CI 136, 63N), poorer voluntary activation (20% CI 13, 25%) that was associated with quadriceps weakness, and impaired acuity of knee joint position sense (1.28 degrees, CI 0.84, 1.73 degrees). As a group the patients were more unstable (p = 0.0017), disabled (10, CI 7, 11), and had poorer functional performance (19.6 seconds, CI 14.3, 24.9 seconds). The most important predictors of disability were objective functional performance and quadriceps strength. CONCLUSIONS: In patients with knee OA, articular damage may reduce quadriceps motoneurone excitability, which decreases voluntary quadriceps activation thus contributing to quadriceps weakness, and diminishes proprioceptive acuity. The arthrogenic impairment in quadriceps sensorimotor function and decreased postural stability was associated with reduced functional performance of the patients.

Activities of Daily Living↗
PubMed1997

Effect of manual therapy techniques on the stretch reflex in normal human quadriceps.

The effect of four manual therapy techniques on the quadriceps stretch reflex amplitude (elicited by mechanical vibration) was studied in a randomized, controlled trial in 120 (20 in each of six groups) healthy human subjects aged 18-64 years. Passive and active techniques were studied; each under static and dynamic conditions. The passive procedures were massage (static) and knee oscillation (dynamic) for 5 min. Active techniques involved eight repetitions of isometric quadriceps contractions (static) and leg extension (dynamic). The two static techniques had no effect on the stretch reflex amplitude. Both dynamic techniques caused a reduction (active by 25%, p < 0.00001 and passive 12%, p < 0.05). Only the active, dynamic technique caused a greater change than in the control group (p < 0.005). The effect lasted for less than 1 min. These data question the ability of such techniques to make clinically valid changes in motoneuron excitability. Further studies are required on those with neuromuscular pathology, who may respond differently to normal subjects.

Adult↗
PubMed1996

The effect of eccentric exercise on serum creatine kinase activity in different ethnic groups.

Eccentric exercise causes release of muscle creatine kinase (CK) 3-4 days after exercise. Racial variation in basal serum CK has been reported but the reasons for this are unknown. We studied 30 subjects of different ethnic origin (Caucasian, Afro-Caribbean, Asian) before and after eccentric exercise. Basal serum CK was significantly higher in the Afro-Caribbean group (201 +/- 134 IU/L, median +/- SD) compared to Caucasians (81 +/- 57 IU/L). The Asian group had intermediate CK values (144 +/- 93 IU/L). The intra-individual range of peak post-exercise CK values obtained was very wide (95-30 200 IU/L) with little difference in median CK between the Afro-Caribbean (8450 +/- 9020 IU/L) and Caucasian groups (7600 +/- 8800 IU/L). The median value for the Asian group was lower (594 +/- 5410 IU/L). A sub-group of 15 individuals undertook a second bout of exercise 2 weeks later and all subjects demonstrated a training effect resulting in a marked attenuation of enzyme efflux. The variation in CK between the ethnic groups was not related to measurements of muscle strength or body mass, although the torque: body mass ratio followed the same order as the basal CK, i.e. the Afro-Caribbeans had the highest values. These results highlight the importance of considering ethnic origin and previous exercise history when interpreting serum CK assay results.

Adult↗
PubMed1996

Electrical and mechanical output of the knee muscles during isometric and isokinetic activity in stroke and healthy adults.

Surface electromyography (EMG) and torque were measured from knee flexors and extensors in 12 control subjects (CS) aged 25-59 years (10 female) and bilaterally in 12 stroke subjects (SS) aged 27-75 years (four female) with hemiparesis and mild clinical spasticity. They performed isometric and isokinetic maximal voluntary contractions (MVC) and also isokinetic passive movements at angular velocities from 30 to 300 degrees/s. The time taken to walk 10 m was documented. Greater torque was recorded during passive extension in the paretic legs when compared with both non-paretic and control limbs (p < 0.01). No EMG activity was measured in any subject. Isometric MVC torque of both muscles in the paretic leg was less (p < 0.01) than both the non-paretic and control limbs. The SS generated relatively less torque bilaterally at the lower velocities than CS. Not all SS reached the higher velocities and none of the paretic limbs achieved 300 degrees/s during flexion. Gait speed correlated with maximal paretic knee extension velocity (p < 0.001). The extent of co-contraction during MVCs was generally low or absent and similar in all three groups. These results suggest a mechanical rather than reflex cause for the restraint detected clinically. Low force generation by the paretic agonists appeared to be the major cause of reduced torque, rather than antagonist opposition.

Adult↗
PubMed1995

The metabolic costs of different types of contractile activity of the human adductor pollicis muscle.

1. The metabolic costs and physiological consequences of shortening contractions of a human muscle working in situ have been compared with those of the muscle maintaining a continuous isometric contraction and when performing repeated brief isometric contractions. 2. After a total of 10 s stimulation, the shortening and intermittent brief isometric protocols had very similar effects, causing a 30% loss of force and a threefold increase in the half-time of relaxation. This was in contrast to the continuous isometric contraction protocol where there was less than 10% loss of force or slowing of relaxation. 3. The ATP cost over the first 5 s of the continuous isometric protocol was 27 mmol (l intracellular water)-1 while for the shortening and repeated brief isometric protocols the costs were 48 and 46 mmol (l intracellular water)-1, respectively. 4. The results show that shortening and repeated brief isometric contractions are considerably more energetically demanding, and hence more fatiguing, than sustained isometric contractions.

Adenosine Triphosphate↗
PubMed1995

Associations between muscle soreness, damage, and fatigue.

Eccentric exercise results in muscle soreness, structural damage, prolonged losses in strength and range of motion, and neuromuscular dysfunction. Greater and longer lasting fatigue occurs after eccentric compared with concentric and isometric exercise. Higher forces are achieved during eccentric contractions with less ATP usage and greater increases in temperature. Although mechanisms involved in the damage and repair process are not well understood, active strain during eccentric contractions is suggested to cause the initial damage which increases over 2-3 days, followed by regeneration.

Energy Metabolism↗
PubMed1994

Arthrogenic quadriceps inhibition and rehabilitation of patients with extensive traumatic knee injuries.

1. The relationship between joint damage, quadriceps weakness and arthrogenic muscle inhibition was investigated in eight patients who had sustained extensive traumatic knee injury. Isometric and isokinetic quadriceps and hamstring voluntary strength, and quadriceps arthrogenic muscle inhibition during isometric contractions, were measured before and after 4 weeks (approximately 100 h) of intensive rehabilitation. 2. Compared with the uninjured leg, before rehabilitation the injured leg had larger amounts of quadriceps arthrogenic muscle inhibition (P < 0.025), quadriceps (P < 0.0001) and hamstring (P < 0.0001) weakness and severe functional joint instability. There was a negative correlation between the amount of arthrogenic muscle inhibition and quadriceps voluntary contraction force (P < 0.025). 3. After rehabilitation in the injured leg there were small hamstring strength increases (P < 0.05-0.025), but no overall significant quadricep strength increase. Arthrogenic muscle inhibition was statistically unchanged. Severe functional joint instability was still reported by all patients. 4. Previous studies have shown that minimal joint damage evokes relatively less arthrogenic muscle inhibition that does not impede rehabilitation. These data indicate that greater joint damage is associated with greater arthrogenic muscle inhibition, quadriceps weakness and joint instability. Furthermore, intensive rehabilitation had little affect on either quadriceps arthrogenic muscle inhibition or atrophy.

Adult↗
PubMed1993

The influence of arthrogenous muscle inhibition on quadriceps rehabilitation of patients with early, unilateral osteoarthritic knees.

Reflex arthrogenous muscle inhibition (AMI) may cause muscle atrophy or impede effective rehabilitation of affected muscle groups. To investigate this, bilateral quadriceps AMI, isometric and isokinetic muscle strength were measured in 10 patients with unilateral osteoarthritic knees, before and after a course of routine physiotherapy. Before rehabilitation, quadriceps of all the diseased legs were inhibited (P < 0.05) and 40% weaker (P < 0.02) than the non-diseased legs. Following rehabilitation, AMI decreased (P < 0.01) in the diseased leg and strength increased at all test velocities (P < 0.05-0.005); however, strength deficits compared with the non-diseased leg remained. Subjective improvements in functional ability and confidence in the diseased leg were reported. Though AMI may be partially responsible for unilateral muscle weakness, it does not preclude strength gain in affected muscles. Possible physiological mechanisms which evoke AMI may also adversely affect muscle proprioception, implicating AMI as a possible cause of initiation or progression of degenerative joint disease.

Adult↗
PubMed1991

Muscle biochemistry and pathophysiology in postviral fatigue syndrome.

Patients with postviral fatigue syndrome (PVFS) usually complain of the skeletal muscle-related symptoms of fatigue and myalgia. It is not surprising therefore that the muscles have recently been the object of intensive studies which have used a variety of biochemical and physiological techniques. The aim of this chapter is to review these findings, and to discuss their significance or otherwise to the presenting symptoms and course of the condition.

Fatigue Syndrome, Chronic↗
PubMed1991

Voluntary activation of human quadriceps during and after isokinetic exercise.

The extent of voluntary activation in fresh and fatigued quadriceps muscles was investigated during isometric and isokinetic voluntary contractions at 20 and 150 degrees/s in 23 normal human subjects. The muscles were fatigued by a total of 4 min of maximal knee extension at an angular velocity of 85 degrees/s. Voluntary activation was determined by the superimposition of tetanic electrical stimulation at 100 Hz for 250 ms, initiated at a constant knee angle. The relationship between voluntary and stimulated force was similar to that found with the established twitch superimposition technique used on isometric contractions. In fresh muscle all the subjects showed full voluntary activation during isometric contractions. Some activation failure was seen in five subjects at 20 degrees/s [2.0 +/- 0.9 degrees (SE)] and in two subjects at 150 degrees/s (0.7 +/- 0.5). After fatigue all subjects showed some activation failure at 0 and 20 degrees/s (36.4 +/- 3.1 and 28.8 +/- 4.1 degrees, respectively), but only two showed any at 150 degrees/s (1.4 +/- 5.7). We conclude that brief high-intensity dynamic exercise can cause a considerable failure of voluntary activation. This failure was most marked during isometric and the lower-velocity isokinetic contractions. Thus a failure of voluntary activation may have greater functional significance than previous studies of isometric contractions have indicated.

Adult↗
PubMed1990

A 31P study of fatigue and metabolism in human skeletal muscle with voluntary, intermittent contractions at different forces.

Normal subjects performed voluntary, isometric exercise 1 s contraction, 1 s rest for 10 min) of the first dorsal interosseous (FDI) muscle with a target force of 25, 50 and 100% of the maximal voluntary contraction (MVC) force. 31P NMR spectra were collected continuously before, during and after exercise. Data were also taken from the resting muscles 2-28 h after the studies at 50% MVC. Calculations were made of the intracellular pH and concentrations of PCr, Pi, ATP, ADP and H2PO4-. The 25% MVC contractions did not affect the MVC, but those at 50 and 100% MVC reduced the force by 20% and 60%, respectively (p less than 0.005). During the highest force contractions, the MVC declined from the first minute but the target forces of 25 and 50% were maintained throughout. All protocols caused significant changes in pH, PCr, Pi, ADP and H2PO4-. Exercise at 50% MVC caused greater metabolic changes than that at 25%, but there was no overall difference in the pH and phosphorus metabolites between the two higher forces. In parallel studies, electrical stimulation of the muscle indicated that during the voluntary contractions with a target force of 100% MVC in the magnet: (a), additional muscles were being used to generate the recorded force; and (b), the subjects were not fully activating the FDI. There was no obvious causal relationship between any one metabolite and the decline of force. Resting muscle showed an increase in the Pi peak 2-28 h after exercise at 50% MVC force, despite the muscles being of full strength and pain free.

Cytosol↗