Rehabilitation following Myocardial Infarction

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This research was conducted at the the British Military’s Joint Services Medical Rehabilitation Unit based at Headley Court in Surrey. The work was carried out by Anthony J Sargeant (later Professor) under the clinical supervision of the Director of the Rehabilitation Unit’s Wing Commander Dr MA (Tony) Crawley.
Archives of Physical Medicine and Rehabilitation
Arch Phys Med Rehabil. 1979 Mar;60(3):121-5.

The physiological responses to exercise were studied in 16 men (33-52 years of age), 8–12 weeks after a first uncomplicated myocardial infarction and following a 3–4 week period of attendance at a residential rehabilitation center at which the patients were required to participate in a controlled program of exercise, sport and recreation. Data were also collected on an inactive, but otherwise healthy group of men of the same age and occupational status, and on an occupationally and recreationally active healthy group. The patient group were indistinguishable from the healthy inactive group in their response to submaximal exercise, although both of these groups showed differences when compared with the active group.

Symptom-limited maximal data were also collected and these are reported in relation to the energy requirements of some common leisure, occupational and domestic activities.

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Important methodological paper on a technique for measuring human forces generated in cycling

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The early development of strain gauge technology applied to the cranks of a stationary cycle ergometer using phosphor bronze contacts and sliding ring design.Research initiated by Tony Sargeant but absolutely dependent on the brilliant engineering expertise of Alec Charters (instrument maker) and Ted Reeves (electrical engineer)

Efficiency of Human Muscle – a Collaboration between Manchester and Copenhagen

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A study based on earlier work by Professor Anthony J Sargeant and carried out under his direction by Richard Ferguson his PhD student working with colleagues in Copenhagen headed up by Jens Bangsbo.
Journal of Physiology
J Physiol. 2001 Oct 1;536(Pt 1):261-71.

1. It has been established that pulmonary oxygen uptake is greater during cycle exercise in humans at high compared to low contraction frequencies. However, it is unclear whether this is due to more work being performed at the high frequencies and whether the energy turnover of the working muscles is higher.

The present study tested the hypothesis that human skeletal muscle oxygen uptake and energy turnover are elevated during exercise at high compared to low contraction frequency when the total power output is the same.

2. Seven subjects performed single-leg dynamic knee-extensor exercise for 10 min at contraction frequencies of 60 and 100 r.p.m. where the total power output (comprising the sum of external and internal power output) was matched between frequencies (54 +/- 5 vs. 56 +/- 5 W; mean +/- S.E.M.). Muscle oxygen uptake was determined from measurements of thigh blood flow and femoral arterial – venous differences for oxygen content (a-v O(2) diff). Anaerobic energy turnover was estimated from measurements of lactate release and muscle lactate accumulation as well as muscle ATP and phosphocreatine (PCr) utilisation based on analysis of muscle biopsies obtained before and after each exercise bout.

3. Whilst a-v O(2) diff was the same between contraction frequencies during exercise, thigh blood flow was higher (P < 0.05) at 100 compared to 60 r.p.m. Thus, muscle V(O2) was higher (P < 0.05) during exercise at 100 r.p.m. Muscle V(O2) increased (P < 0.05) by 0.06 +/- 0.03 (12 %) and 0.09 +/- 0.03 l min(-1) (14 %) from the third minute to the end of exercise at 60 and 100 r.p.m., respectively, but there was no difference between the two frequencies.

4. Muscle PCr decreased by 8.1 +/- 1.7 and 9.1 +/- 2.0 mmol (kg wet wt)(-1), and muscle lactate increased to 6.8 +/- 2.1 and 9.8 +/- 2.5 mmol (kg wet wt)(-1) during exercise at 60 and 100 r.p.m., respectively. The total release of lactate during exercise was 48.7 +/- 8.8 and 64.3 +/- 10.6 mmol at 60 and 100 r.p.m. (not significant, NS). The total anaerobic ATP production was 47 +/- 8 and 61 +/- 12 mmol kg(-1), respectively (NS).

5. Muscle temperature increased (P < 0.05) from 35.8 +/- 0.3 to 38.2 +/- 0.2 degrees C at 60 r.p.m. and from 35.9 +/- 0.3 to 38.4 +/- 0.3 degrees C at 100 r.p.m. Between 1 and 7 min muscle temperature was higher (P < 0.05) at 100 compared to 60 r.p.m.

6. The estimated mean rate of energy turnover during exercise was higher (P < 0.05) at 100 compared to 60 r.p.m. (238 +/- 16 vs. 194 +/- 11 J s(-1)). Thus, mechanical efficiency was lower (P < 0.05) at 100 r.p.m. (24 +/- 2 %) compared to 60 r.p.m. (28 +/- 3 %). Correspondingly, efficiency expressed as work per mol ATP was lower (P < 0.05) at 100 than at 60 r.p.m. (22.5 +/- 2.1 vs. 26.5 +/- 2.5 J (mmol ATP)(-1)). 7. The present study showed that muscle oxygen uptake and energy turnover are elevated during dynamic contractions at a frequency of 100 compared with 60 r.p.m. It was also observed that muscle oxygen uptake increased as exercise progressed in a manner that was not solely related to the increase in muscle temperature and lactate accumulation

Research into Post polio syndrome (PPS)

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Dr Frans Nollet carried out this research as part of his PhD which was supervised by Tony Sargeant in Amsterdam.
Archives of Physical Medicine and Rehabilitation
Arch Phys Med Rehabil. 2001 Dec;82(12):1678-85.

Abstract

OBJECTIVES: To compare the submaximal exercise capacity of polio subjects with postpoliomyelitis syndrome (PPS) and without (non-PPS) with that of healthy control subjects, to investigate the relationship of this capacity with maximal short-term power and quadriceps strength, and to evaluate movement economy.

PARTICIPANTS: Forty-three polio subjects (25 PPS, 18 non-PPS) and 12 control subjects. MAIN OUTCOME MEASURES: Power output, oxygen uptake, and heart rate were measured in an incremental submaximal cycle ergometry test. Maximal short-term power was measured in 5-second all-out efforts. Knee extensor strength was measured on a chair dynamometer.

RESULTS: The mean submaximal power +/- standard deviation at 80% of heart rate reserve of 83.8 +/- 29.9 watts in the polio subjects was significantly less than the mean submaximal power of 142.1 +/- 30.4 watts in the control group. However, expressed as a percentage of the maximal short-term power, submaximal power did not differ between the groups. Strength and maximal short-term power correlated significantly (p < .005) with submaximal power (r = .64 and .76, respectively). The oxygen uptake was higher than theoretically expected for the given submaximal power output in polio subjects, and appeared to increase with increasing asymmetry in strength and power between legs. No differences were found between PPS and non-PPS subjects.

CONCLUSION: The submaximal work capacity of polio subjects was severely reduced, mainly in association with the reduced muscle capacity. And, because of a reduced movement economy, their energy cost was elevated. Although muscle loads in activities such as walking and climbing stairs differ from cycling, they also may require elevated relative levels of effort, predisposing subjects to premature fatigue in sustained activity

Training of leg muscle in spinal cord injured people using electrical stimulation

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Collaborative research carried out in Amsterdam and Nijmegen and in collaboration with Professor David Jones of Birmingham University studied the effect of using different frequencies of electrical stimulation when training leg muscles of spinal cord injured people.
Muscle & Nerve 2002 Apr;25(4):559-67.

Effects of two different training regimens on the contractile properties of the quadriceps muscle were studied in six individuals with spinal cord injury. Each subject had both limbs trained with the two regimens, consisting of stimulation with low frequencies (LF) at 10 HZ or high frequencies (HF) at 50 HZ; one limb of each subject was stimulated with the LF protocol and the other with the HF regimen. Twelve weeks of daily training increased tetanic tension by approximately 20%, which was not significantly different between training regimens.

Interestingly, after HF but not LF training, the unusual high forces at the low frequency range of the force-frequency relationship decreased, possibly due to a reduced activation per impulse. After LF but not HF training, force oscillation amplitudes declined (by 33%) as relaxation tended to slow, which may have opposed possible effects of reduced activation as seen after HF training. Finally, fatigue resistance also increased rapidly after LF training (by 43%) but not after HF training. These results indicate that different types of training may selectively change different aspects of function in disused muscles.

Muscle force after immobilization in plaster casts following leg fracture

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In this interesting research study using new and novel techniques Professor Anthony J Sargeant was able to show how during rehabilitation of young Military personnel work was shared unequally between a previously injured compared with an uninjured leg. In the bipedal cycling task the contribution of work from the previously injured leg was 40% of that of the uninjured leg. The difference in forces generated and work performed was similar to the massive loss of muscle fibre cross-sectional area reported in another study published in the same year (Clinical Science and Molecular Medicine. 1977 Apr;52(4):337-342). Clearly asymmetry of this magnitude may well explain why, many years after injury, a difference in muscle size and function often persists despite intensive rehabilitation (but rehabilitation which often involves bipedal exercise).
Clinical Science and Molecular Medicine
Clin Sci Mol Med. 1977 Aug;53(2):183-8

1. Six patients were studied after prolonged immobilization of an injured leg resulting in muscle atrophy.

2. The forces exerted by the atrophied and normal legs during continuous dynamic exercise (one- and two-leg cycling) were examined by a specially adapted ergometer.

3. In one-leg cycling the peak force exerted on the crank at a given work rate, the net work rate performed on the crank, and the proportion of work rate performed in leg extension and flexion phases of the cycle were the same whether the atrophied or normal limb was used.

4. Despite these similarities there was an unexplained reduction in efficiency when using the atrophied leg to perform one-leg cycling.

5. In two-leg cycling the peak force exerted at a given work rate by the atrophied leg was reduced by about 40% as compared with the normal leg, which reflected a similar reduction in the contribution of that leg to the total net work rate. Possible reasons and implications for this disproportionate sharing of work between the normal and atrophied leg are discussed