Browsing by Author "Mars, Maurice."

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A Comparison of upper and lower limb exercise in canoeists using the heart rate and oxygen consumption relationship
(2003) Gomes, Adrian Neil.; Mars, Maurice.
The heart rate achieved with maximal upper limb exercise is quoted as being on average thirteen beats per minute lower than when performing maximal leg exercise. Many canoeists use heart rate monitors during training and seek advice on setting their heart rate training zones. Existing guidelines are based on lower limb-derived heart rates, which may not be appropriate. As canoeists use predominantly their upper limbs during canoeing, it was hypothesized that as their upper limbs are trained, they may achieve heart rates and oxygen consumption similar to those achieved with lower limb exercise. The purpose of this investigation was to compare the relationship between heart rate and oxygen consumption when exercising on either a kayak ergometer or treadmill. Fifteen volunteer canoeists, who compete regularly, were recruited by convenience, purposive sampling and randomly allocated to a V02max test using open circuit spirometry, on either a kayak ergometer or treadmill. They returned within 5 to 7 days for a V02max test on the other apparatus. Their heart rates were also measured during these activities. The heart rate oxygen consumption relationship for upper and lower limb exercise was then analysed. Maximum heart rate was on average only 6 beats per minute lower with upper limb exercise, with some subjects achieving the same or very similar HRmax; the median difference in heart rate maximum was only 4 beats per minute. Although the response of heart rate and oxygen consumption to kayaking and running was similar at any given workload, the heart rate on the kayak was about 8 beats per minute higher at any submaximal workload. V02max. on the kayak was lower than on the treadmill. At any metabolic equivalent, the tidal volume was lower on the kayak and there was a lower respiratory rate on the treadmill. At any tidal volume, the metabolic equivalent was lower on the kayak ergometer. The minute volume on the kayak was higher than on the treadmill, for all but the highest intensities of exercise. Using the leg heart rate max to determine the training zones, a slightly higher (negligible) percentage of arm V0max is achieved at any given percentage heart rate. Kayakers who train regularly, appear to be able to attain similar maximum heart rates with upper and lower limb exercise, but a lower V02max when exercising with their arms. The heart rate oxygen consumption response is the same for upper and lower body exercise; and a reduced HRmax and increased heart rate at any sub maximal workload do not appear to apply to canoeists. It is therefore concluded that heart rate training zones based on leg HRmax are suitable for kayak training. This study has helped distinguish the difference between the heart rates of the upper and lower limbs at any given oxygen consumption in canoeists. The benefits of performing this study have also been to provide better advice to canoeists on how to train using heart rate monitors.
The determination of unilateral ratios (knee and shoulder muscle strength), of provincial cricketers.
(2002) Lock, Natasha.; Mars, Maurice.
Abstract available in PDF.
The effect of ultradistance running on premenopausal women of different ethnic groups.
(2005) McGregor, Avril.; Mars, Maurice.; Cassim, Bilkish.
No abstract available.
The effects of high intensity exercise on lymphocyte DNA and antioxidant status in trained athletes.
(1998) Govender, Sumentheran Nadarajan.; Chuturgoon, Anil Amichund.; Mars, Maurice.
Apoptosis (programmed cell death) and exercise immunology have been the focus of research for the past five years. Trained athletes are particularly susceptible to a wide variety of viral and bacterial infections and this has been related to oxidative damage which is a mediator of apoptosis. Apoptosis, a normal physiological mechanism has also been implicated in the pathogenesis of a wide-variety of diseases. To date, the link between apoptosis and exercise has not been shown by established methods or ultrastructurally. The objective of the study was t.o determine the effects of a single bout of high intensity exercise on lymphocyte DNA and antioxidant status in trained athletes. The study was carried out in two phases. In the first phase, 11 trained athletes were subjected to a treadmill run to exhaustion using a ramp protocol to determine their maximum oxygen uptake (V02 max). Fifteen millimetres of blood was collected before exercise, immediately after exercise, 24 hours and 48 hours after exercise. Whole blood (4 ul) was used in the determination of DNA damage in lymphocytes using the single cell gel electrophoresis (SCGE) assay. The remaining blood was centrifuged and used for the following: Vitamin C concentration was determined by the 2,4 dinitrophenylhydrazine method, vitamin E concentration was determined by the High Pressure Liquid Chromatography (HPLC) method and lipid peroxides were determined by the measurement ofhydroperoxides. In the second phase, 3 trained athletes who had participated in phase 1, were subjected to a V02 max. test. Blood samples (10 ml) were collected before and immediately after exercise, 24 hours and 48 hours later. Lymphocytes were isolated using Histopaque 1077. An in situ cell death detection kit, Fluorescein was used for the detection and quantification of apoptosis in lymphocytes at a single cell level, based on labelling of DNA strand breaks. Analysis was carried out using flow cytometry. Lymphocytes were also prepared for Transmission Electron Microscopy (TEM) using conventional techniques. The results showed that immediately after exercise there was a non-significant decrease in vitamin C concentrations (p=o, 16), and a non-significant increase in vitamin E (p=0,82) and lipid peroxide concentrations (p=0,21). There was no significant difference in all 3 levels over the 48 hour period, when compared to the pre-exercise values. The SCGE assay revealed that the immediate post exercise samples showed DNA damage in lymphocytes of all subjects as evidenced by fluorescent strands of DNA outside the cell while DNA damage was observed in only one subsequent sample. In the pre-exercise samples, DNA was visualised as a central core, whereas in all samples taken after exercise, DNA was located at the periphery or confined to one pole of the cell. The pattern of DNA distribution seen in the SCGE assay over the 48 hour period were characteristic features of apoptosis. Flow cytometric analysis showed an increase in apoptosis in lymphocytes immediately after exercise with a further increase after 24 hours. After 48 hours the numbers decreased to control levels. TEM showed that majority of cells were normal before exercise while other lymphocytes were smaller with indented nuclei. Immediately after exercise the lymphocytes displayed features of indented nuclei and microsegregation, cell shrinkage, swelling of the endoplasmic reticulum, mitochondria and Golgi. These changes persisted after 24 hours but were not observed after 48 hours when most of the cells showed normal morphology. The ultrastructural changes observed were also characteristic features of apoptosis. These results suggest that high intensity exercise may cause an increase in apoptosis as evidenced by DNA damage in the SCGE assay and fully supported by the results achieved during flow cytometry and by the ultrastructural changes observed.
An evaluation of the use of transcutaneous oxygen pressure measurement in the non-invasive vascular laboratory : with special reference to selection of amputation level.
(2001) Mars, Maurice.; Robbs, John Vivian.
Transcutaneous oxygen pressure measurement (TCp02) using a miniaturised Clarke electrode and a heating thermistor was developed independently by Huch et al and Eberhardt et al in 1972. After its initial use to non invasively monitor arterial partial pressure (Pa02) in neonates it was proposed as a useful test of skin blood flow and possibly amputation wound healing level selection in patients with peripheral vascular disease. Unfortunately a wide range of predictive values emerged with some authors reporting amputations healing when the TCp02 value was 0 mmHg. The investigation, while still considered useful, has not gained widespread support. This study investigates the use of TCp02, establishes a value for the use of the TCp02 Index to predict amputation wound healing potential and examines the hypothesis that the use of the TcpO Index to select amputation level can reduce patient morbidity and mortality. The literature is reviewed and a series of studies evaluating TCp02 use, undertaken in the Durban Metropolitan Vascular Service Non-Invasive Laboratories, are presented. TCp02 measurements were performed in a standardised manner with the subject supine breathing room air. Measurements were taken at fixed sites, on the mid dorsum of the foot (Foot), 10 cm distal to the tibial tuberosity and 2 cm lateral to the anterior tibial margin (BKA), 10 cm proximal to the patella in the midline (AKA) and on the chest in the mid-clavicular line. A TCp02 Index, the limb to chest ratio was defined. TCp02 data derived from control subjects asymptomatic of peripheral vascular disease were shown to be similar to age matched pooled data derived from the literature. In patients with peripheral vascular disease, absolute TCp02 and the TCp02 Index were shown to fall from proximal to distal sites and again were no different to pooled data derived from the literature. Based on presenting symptoms, the fall in TCp02 and the TCp02 Index was significant from proximal to distal sites. The reduction in absolute TCp02 and the TCp02 was also related to the most distal pulse present. TCp02 values were found to be no different in patients with peripheral vascular disease with or without diabetes. When comparing TCp02 and the TCp02 Index with Doppler pressure measurements at the Popliteal artery and at the foot, and the Doppler ankle brachial index (ABI), Doppler derived data were significantly higher in diabetic patients than in non-diabetic patients. No differences were noted in TCp02 data. TCp02 was compared with the 133Xe radio-isotope skin washout test. The best correlation was (r = 0.46) was obtained with a logarithmic curve y = 10.862Ln(x) + 38.751. TCp02 was compared with antibiotic concentrations (Cefoxitin) in muscle obtained from the site of amputation and the Cefoxitin Index, the ratio of muscle antibiotic concentration to plasma concentration, as an indication of the relationship of skin TCp02 to muscle blood flow. A significant correlation was shown between the Cefoxitin Index and TCp02 (r = 0.67, p = 0.035) and the TCp02 Index (r = 0.64, P = 0.045), suggesting that skin oxygen delivery may reflect muscle antibiotic delivery and hence blood flow. TCp02 and the TCp02 Index were compared with heated and unheated laser Doppler fluxmetry (LDF) in 35 patients undergoing amputation wound healing assessment. Significant correlations were shown between heated LDF, heated LDF Index and the TCp02 Index (r = 0.63 and r = 0.69, P < 0.0001). TCp02 Index values of 0.5 and 0.55 showed an accuracy of 96.2 % in predicting amputation outcome while LDF values of 3, 4 and 5 arbitrary units gave an accuracy of 88.5 %. Using receiver operator curves, a TCp02 Index of 0.55 was shown to be the best test. Over the years 1987 and 1988, TCp02 data were gathered on 193 patients undergoing lower limb amputation for peripheral vascular disease. Information on the outcome of the amputation was available for 152 amputations. Circumstances which might result in a reduced pre-operative TCp02 reading were identified and criteria were set for the use of TCp02 to predict amputation wound healing potential. 122 amputations which met the defined entry criteria were available for evaluation. A TCp02 Index of 0.50 gave a definitive predictive value below which no amputation healed. Similarly no amputation with an absolute TCp02 of less than 27 mmHg healed. Receiver operator characteristic curves showed the TCp02 Index to be a better test than absolute TCp02. A TCp02 Index of 0.55 was shown to have the best sensitivity of96.7 %, with a specificity of79.8 % and an accuracy of 90.2 %. When introduced to clinical practice, correct use of the TCp02 Index of 0.55 resulted in a reduction in amputation revision rate from 40.3 % in 1987, to 8.2 % in 1990. Initially some surgeons felt that the TCp02 Index predicted amputation wound failure at distal sites at which healing could be expected on clinical criteria, and chose amputate at sites with a TCp02 Index value less than 0.55. These amputations failed to heal. As surgeons gained confidence in the test, they chose to follow the TCp02 data more often and the percentage of amputations performed at sites predicted by the TCp02 Index to fail , fell from 35.5 % in 1987 to 6.6 % in 1990. Over a 15 year period at King Edward VIII Hospital, the amputation revision rate has fallen from an average of 32.7 % in the first five years when Tcp02 data were not available to the surgeon, to 21.4 % and 22.9 % in the two subsequent 5 year periods when Tcp02 data were available. The mortality rates were unchanged. The decline in revision rates was less than expected and relates to the fact that approximately only 42 % of patients requiring amputation undergo the test. This is because it is time consuming and available only during weekday office hours. These studies have confirmed the usefulness of Tcp02 measurement in the non-invasive vascular laboratory. The index is shown to be superior to absolute Tcp02 as a predictive test of amputation wound healing. The introduction of several criteria to define when Tcp02 use is appropriate has refined the investigation and made it clinically useful in our setting. A Tcp02 Index of 0.55 in the appropriate patient is a useful test to predict amputation wound healing and its use has resulted in reduced patient morbidity and mortality, confirming the hypothesis tested.
An investigation into the causes of illness in the 1996 Dusi canoe marathon.
(1997) Foreman, S. E.; Mars, Maurice.
Abstract available in PDF.
Investigation of increasing running cadence as a means of determining exercise intensity for aerobic training using a mini-trampoline.
(1997) Khan, Anwar.; Mars, Maurice.; Weston, A.
Abstract available in PDF.
Knowledge, attitude and perception of 4th and 5th year UKZN medical school students towards the use of HIV drug resistance interpretation algorithms.
(2013) Zhandire, Tracy.; Singh, Yashik.; Mars, Maurice.
HIV drug resistance (HIVDR) has emerged as a major clinical and public health challenge in many resource poor countries especially in Africa. HIVDR testing has become increasingly important and is of significant value in the management of HIV. The use of low cost technologies and procedures in testing HIVDR is being recommended. HIVDR computer interpretation algorithms make use of artificial intelligence and other computer technologies to predict HIVDR, and are recommended for use in resource poor countries. However, there is little known about the knowledge, attitude and perception of HIVDR computer algorithms by doctors in developing countries who are supposed to use computer algorithms. This study aimed to determine the knowledge, attitude and perception regarding computer interpretation algorithms of the 4th and 5th year medical students at Nelson R. Mandela School of Medicine, University of KwaZulu Natal in South Africa. Primary data collection was done using a questionnaire administered to a convenience sample of 216 4th and 5th year medical students. The study revealed that 90% of the respondents were aware of HIV drug resistance testing in South Africa but only 4% had knowledge of the computer interpretation algorithms. The study revealed that although the UKZN medical students are not aware of computer interpretation algorithms, majority are willing to use them in the future.
Role of massage and stretching in recovery from exercise and in delayed onset muscle soreness.
(1997) Viranna, N. V.; Mars, Maurice.
Adequate recovery from intense exercise is essential to optimise performance and reduce the associated symptoms of tiredness, fatigue and lethargy. The purpose of the study was to :- i. investigate the effects of massage and stretching in delaying the development of fatigue during repeated bouts of dynamic activity and, ii. to investigate the relative effects of massage and stretching on delayed onset muscle soreness (DOMS). Eighteen volunteer males participated in this study. They were randomly allocated into one of six groups of an Orthogonal Latin square design. Subjects performed five repetitions of as many heel raises as possible in 45 seconds. Each repetition was followed by a recovery technique of three minutes duration. This was repeated weekly until each group has had all three recovery techniques. A fatigue index % was calculated from the decline in the number of repetitions from stage 1 to stage 5. Muscle soreness ratings were retrospectively assessed at 12-36 hour after each session. An analysis of variance showed a significant difference in the fatigue indices. Post hoc intergroup comparison using paired T-tests with the Bonferroni adjustment showed a significant difference between rest and massage (p=0.0001) and rest and stretching (p=0.0006). The differences between massage and stretching were not significant. Fourteen (77.8%) and Fifteen (83.3%) subjects showed an improvement in performance following massage and stretching respectively. Massage is associated with significantly less muscle soreness than stretching (p<0,001). DOMS was most frequently found in the stretching group while the lowest incidence and lowest mean ratings of muscle soreness associated with DOMS was found in the massage group. The difference between massage and stretching was marginal (p=046I) and showed a trend that massage is associated with less DOMS than stretching. This suggests that rest is the least beneficial recovery technique, and that massage may be superior to stretching as there is less muscle soreness.
The use of laser doppler fluxmetry in the pre-operative assessment of amputation wound healing in the dysvascular patient.
(1997) McKune, Andrew James.; Mars, Maurice.; Robbs, John Vivian.
Abstract available in PDF.