Biomedical subjects

T D Noakes

Publications and source records attributed to T D Noakes.

At least 145 records · Page 8Linked to original sources

PubMed1996

Effects of medium-chain triglyceride ingestion on fuel metabolism and cycling performance.

On three occasions separated by 10 days, six endurance-trained cyclists rode for 2 h at 60% of peak O2 uptake and then performed a simulated 40-km time trial (T-trial). During the rides, the subjects ingested a total of 2 liters of a [U-14C]glucose-labeled beverage containing a random order of either 10% glucose [carbohydrate (CHO)], 4.3% medium-chain triglycerides (MCTs); or 10% glucose + 4.3% MCTs (CHO+MCT). Although replacing CHO with MCTs slowed the T-trials from 66.8 +/- 0.4 (SE) to 72.1 +/- 0.6 min (P < 0.001), adding MCTs to CHO improved the T-trials from 66.8 +/- 0.4 to 65.1 +/- 0.5 min (P < 0.05). Faster T-trials in the CHO+MCT trial than in the CHO trial were associated with increased final circulating concentrations of free fatty acids (0.58 +/- 0.09 vs. 0.36 +/- 0.06 mmol/l; P < 0.05) and ketones (1.51 +/- 0.25 vs. 0.51 +/- 0.07 mmol/l; P < 0.01) and decreased final circulating concentrations of glucose (5.2 +/- 0.2 vs. 6.3 +/- 0.3 mmol/l; P < 0.01) and lactate (1.9 +/- 0.4 vs. 3.7 +/- 0.5 mmol/l; P < 0.05). Adding MCTs to ingested CHO reduced total CHO oxidation rates from 14 +/- 1 to 10 +/- 1 mmol/min at 2 h and from 17 +/- 1 to 14 +/- 1 mmol/min in the T-trial (P < 0.01), without affecting the corresponding approximately 5 and approximately 7 mmol/min rates of [14C]glucose oxidation. These data suggest that MCT oxidation decreased the direct and/or indirect (via lactate) oxidation of muscle glycogen. A reduced reliance on CHO oxidation at a given O2 uptake is similar to an endurance-training effect, and that may explain the improved T-trial performances.

Adult↗

PubMed1996

Pseudoephedrine is without ergogenic effects during prolonged exercise.

This study was designed to measure whether a single dose of 120 mg pseudoephedrine ingested 120 min before exercise influences performance during 1 h of high-intensity exercise. The effects of exercise on urinary excretion of the drug were also studied. Ten healthy male cyclists were tested on two occasions, separated by at least 7 days, by using a randomly assigned, double-blind, placebo-controlled, crossover design. Exercise performance was tested during a 40-km trial on a laboratory cycle ergometer, and skeletal muscle function was measured during isometric contractions. On a third occasion, subjects ingested 120 mg pseudoephedrine but did not exercise [control (C)]. Pseudoephedrine did not influence either time trial performance [drug (D) vs. placebo: 58.1 +/- 1.4 (SE) vs. 58.7 +/- 1.5 min] or isometric muscle function. Urinary pseudoephedrine concentrations were significantly increased 1 h after exercise (D vs. C: 114.3 +/- 27.2 vs. 35.4 +/- 13.1 micrograms/ml; P < 0.05). Peak plasma pseudoephedrine concentrations (P < 0.05) but not time taken to reach peak plasma concentrations or the area under the plasma pseudoephedrine concentration vs. time curve was significantly increased in the total group with exercise (D vs. C). In three subjects, plasma pseudoephedrine concentrations were not influenced by exercise. Only these subjects showed increased urinary pseudoephedrine excretion during exercise. We conclude that a single therapeutic dose of pseudoephedrine did not have a measurable ergogenic effect during high-intensity exercise of 1-h duration, but plasma drug concentrations and urinary excretion were altered by exercise. These findings have practical relevance to doping control regulations in international sporting competitions.

Adult↗

PubMed1996

Inadequate pre-season preparation of schoolboy rugby players--a survey of players at 25 Cape Province high schools.

OBJECTIVE: To establish the previous rugby experience, the knowledge and the use of injury prevention techniques by South African schoolboy rugby players. DESIGN: Before the first full-contact match of the 1991 rugby season, 2,330 players completed a detailed questionnaire. SETTING: High schools in the Cape Province. Three thousand three hundred and thirty players from 25 schools selected because of a record of excellence in and commitment to schoolboy rugby. MAIN OUTCOME MEASURES: Personal data including age, height, mass and rugby experience; history and nature of previous rugby injuries; knowledge of techniques known to prevent rugby injuries; parental and personal reasons for playing rugby. RESULTS: The incidence and distribution of the different types of injuries previously sustained by the players were the same as those identified prospectively in the same population. A-team players were significantly heavier and taller than players in lower teams in most playing positions in most age groups. Although A-team players were more likely to participate in pre-season endurance or strength training, fewer than 40% of players overall trained adequately in the pre-season. Less than 30 minutes was allocated to the practice of tackling and falling techniques prior to the first full-contact match. Knowledge of different high-risk situations during play was generally sketchy, and only 24% of players wore gumguards all the time. More fathers (84%) than mothers (63%) encouraged their sons to play rugby. CONCLUSIONS: The results indicate that the incidence and nature of the injuries reported retrospectively were similar to those reported in prospective studies at the same schools. The players' knowledge of techniques known to prevent rugby injuries was inadequate and too little attention was paid at the start of the rugby season to training and coaching techniques to reduce injury risk. Coaching errors may therefore have predisposed players to injury.

Adolescent↗

PubMed1996

Is severe left ventricular dysfunction a contraindication to participation in an exercise rehabilitation programme?

OBJECTIVE: To evaluate the effects of an exercise training programme on patients with chronic left ventricular dysfunction. DESIGN: Intervention, before and after the trial. SETTING: Johannesburg Cardiac Rehabilitation Centre, a phase III community-based cardiac rehabilitation facility. PATIENTS: A consecutive sample of 28 patients who were recovering from acute myocardial infarction and who had a left ventricular ejection fraction of 30% or less. Twenty two patients completed the exercise training programme. INTERVENTION: A medically supervised exercise training programme of 6 months' duration. Type of exercise: walking, jogging or cycling. Intensity: 65-85% of the patient's maximal heart rate achieved during treadmill testing. DURATION: 30-45 minutes. Frequency: 3 times a week. Patients who attended fewer than 60% of all prescribed sessions were considered drop-outs. MAIN OUTCOME MEASURES: Haemodynamic, left ventricular function and effort tolerance parameters before and after training. RESULTS: Patients who completed the exercise training programme showed a significant improvement in maximal exercise capacity and a significant reduction in their cardiovascular demands during submaximal exercise. Peak oxygen consumption was increased by 12% after training (19.4 +/- 3 v. 21.8 +/- 4.8 ml/kg/min; P < 0.05) and exercise time to exhaustion by 33% (527 +/- 171 v. 700 +/- 186 seconds; P < 0.001). The double product at the same submaximal workload was significantly reduced (214 +/- 52 v. 194 +/- 44 beats/min x mmHg x 10(2); P < 0.05). These benefits were achieved without any adverse effects on resting (25.4 +/- 5 v. 28.5 +/- 7.9%; P < 0.05) or exercise (27.3 +/- 7.7 v. 29.9 +/- 9.5%; P > 0.05) left ventricular ejection fraction. CONCLUSIONS: Our results show that patients with chronic left ventricular dysfunction can benefit from an exercise training programme and that those benefits can be achieved without risk of further deterioration in left ventricular function. Physical training constitutes another therapeutic option which could be added to the comprehensive management of these patients.

Adult↗

PubMed1996

Intra-operative pneumatic tourniquet--perceptions of use and complications in the orthopaedic community of South Africa.

OBJECTIVES: To assess views on use, maintenance and side-effects of the pneumatic tourniquet in the South African orthopaedic community. METHODS: A census-type questionnaire study was conducted of all 475 orthopaedic surgeons registered with the Orthopaedic Association of South Africa during 1993/94. The chi-square test was used to determine statistical significance between different groups of respondents. RESULTS: Seventy-seven per cent of the questionnaires were returned. Ninety-nine per cent of respondents used a pneumatic tourniquet. Eighty-four per cent believed that the tourniquet may damage underlying tissue both as a result of applied pressure effects and ischaemic consequences. Fifty-four per cent of respondents personally checked the calibration of the pneumatic tourniquet, although 76% of respondents believe that the apparatus needs to be checked at least once per month. More respondents who did not check the tourniquet apparatus than respondents who did check it believe that applied pressure does not cause tissue damage (P < 0.001), that the operating room technician or hospital engineer should be responsible for checking equipment (P < 0.001), and that equipment did not need to be checked more than once every 6 months (P < 0.001). CONCLUSIONS: Although most orthopaedic surgeons are aware of the pneumatic tourniquet's side-effects, a minority appear to be unaware of the hazards of excessive applied pressure alone or excessive applied pressure caused by use of faulty equipment. It needs to be emphasised to these surgeons that regular checking of the pneumatic tourniquet apparatus is necessary in order to prevent postoperative complications ascribed to use of the tourniquet.

Bandages↗

PubMed1995

Role of decreased carbohydrate oxidation on slower rises in ventilation with increasing exercise intensity after training.

In these studies, we examined whether the rightward shift in steady-state minute ventilation (VE) versus O2 uptake curves after training is more closely linked to the reduced CO2 production from carbohydrate oxidation (CHOOX) after training than to the attenuated increase in blood lactate concentration. Steady state VE values and gas exchange were measured in eight previously sedentary men who underwent exercise tests of 60 W + 40 W every 6 min before and after a 9 week training programme of cycling approximately 40 min a day. Following training, the slower rises in VE with increasing exercise intensities were associated with a reduced reliance on CHOOX, (P < 0.01). Both before and after training, VE values in litres per minute rose as a linear VE = 18.CHOOX + 14, function of rates of CHOOX in grams per minute (r = 0.99), irrespective of a marked shift to the right in arterialized venous blood lactate concentration versus CHOOX curves following training (P < 0.01). Thus, slower increases in steady-state VE values with increasing exercise intensities following endurance training appeared to be more closely linked to the decreased reliance on CHOOX than to the attenuated increase in blood lactate concentration.

Adult↗

PubMed1995

Water ingestion does not improve 1-h cycling performance in moderate ambient temperatures.

Eight endurance-trained cyclists rode as far as possible in 1 h on a stationary cycle simulator in a moderate environment (20 degrees C, 60% relative humidity, 3 m.s-1 wind speed) while randomly receiving either no fluid (NF) or attempting to replace their approximate 1.71 sweat loss measured in a previous 1-h familiarisation performance ride at approximately 85% of peak oxygen uptake with artificially sweetened, coloured water (F). During F, the cyclists drank mean 1.49 (SEM 0.14) 1 of which mean 0.27 (SEM 0.08) 1 remained in the stomach at the end of exercise and mean 0.20 (SEM 0.05) 1 was urinated after the trial. Thus, only mean 1.02 (SEM 0.12) 1 of the ingested fluid was available to replace sweat losses during the 1-h performance ride. That fluid decreased the mean average heart rate from 166 (SEM 3) to 157 (SEM 5) beats.min-1 (P < 0.0001) and reduced the final mean serum [Na+] and osmolalities from 143 (SEM 0.6) to 139 (SEM 0.6) matom.l-1 (P < 0.005) and from 294 (SEM 1.7) to 290 (SEM 1.9) mosmol.l-1 (P = 0.05), respectively. Fluid ingestion did not significantly attenuate rises in plasma anti-diuretic hormone and angiotensin concentrations, or decrease the approximate-15% falls in estimated plasma volume in the F and NF trials. Nor did fluid ingestion significantly affect the approximate 1.71.h-1 sweat rates, the rises in rectal temperature (from 36.6 degrees to 38.3 degrees C) or the ratings of perceived exertion in the two trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Effects of endurance training on lactate removal by oxidation and gluconeogenesis during exercise.

This report describes the effects of 9 weeks of endurance-training on the relative rates of lactate removal via oxidation and gluconeogenesis in humans. Before and after training, eight subjects performed incremental (60 W plus 40 W every 6 min) exercise tests, while 14C-lactate was infused into one forearm vein and arterialized venous blood was sampled from the other forearm. During the trial, the volume of expired 14CO2 and circulating 14C-lactate and 14C-glucose specific radioactivities were measured. Such measurements revealed that training increased the estimated oxidation of equivalent venous blood lactate concentrations [VLa] of greater than 1.6 mmol/l. These increases in lactate oxidation were more than would be predicted from the approximately 40% higher O2 uptake values at any [VLa] after training. At a [VLa] of 6 mmol/l, rates of lactate oxidation were increased by some 100% following training, from 105 +/- 12 to 208 +/- 33 micromol/min/kg (P < 0.01). Improvements in lactate oxidation after training reduced the estimated rates of lactate-to-glucose conversion from 40 +/- 3 to 9 +/- 2 micromol/min/kg at a [VLa] of 2.5 mmol/l (P < 0.01). Thus, unlike in rats, human endurance-training does not increase gluconeogenesis. In the final stages of progressive exercise after training, more than 80% of lactate was oxidised and accounted for approximately 45% of overall carbohydrate oxidation.

Adult↗

PubMed1995

Fuel utilisation during prolonged low-to-moderate intensity exercise when ingesting water or carbohydrate.

Previously, we examined the effects of carbohydrate (CHO) ingestion on glucose kinetics during exercise at 70% of maximum O2 uptake (VO2, max). Here we repeat those studies in heavier cyclists (n = 6 per group) cycling for 3 h at a similar absolute O2 uptake but at a lower (55% of VO2, max) relative exercise intensity. During exercise, the cyclists were infused with a 2-3H-glucose tracer and ingested U-14C glucose-labelled solutions of either flavoured water (H2O) or 10 g/100 ml glucose polymer, at a rate of 600 ml/h. Two subjects in the H2O trial fatigued after 2.5 h of exercise. Their rates of glucose appearance (Ra) declined from 2.9 +/- 0.6 to 2.0 +/- 0.1 mmol/min (mean +/- SEM) and, as their plasma glucose concentration [Glu] declined from 4.7 +/- 0.2 to below 3.5 +/- 0.2 mM, their rates of glucose oxidation (Rox) and fat oxidation plateaued at 2.7 +/- 0.4 and 1.7 +/- 0.1 mmol/min respectively. In contrast, all subjects completed the CHO trial. Although CHO ingestion during exercise reduced the final endogenous Ra from 3.4 +/- 0.6 to 0.9 +/- 0.3 mmol/min at the end of exercise, it increased total Ra to 5.5 +/- 0.5 mmol/min (P < 0.05). A higher total Ra with CHO ingestion raised [Glu] from 4.3 +/- 0.3 to 5.3 +/- 0.1 mM and accelerated Rox from 3.5 +/- 0.2 to 5.9 +/- 0.2 mmol/min after 180 min of exercise (P < 0.05). The increased contribution to total energy production from glucose oxidation (34 +/- 1 vs. 20 +/- 1%) decreased energy production from fat oxidation from 51 +/- 2 to 40 +/- 5% (P = 0.08) and produced patterns of glucose, muscle glycogen (plus lactate) and fat utilisation similar to those during exercise at 70% of (V&dot;O2, max). Thus, CHO ingestion is necessary to sustain even prolonged, low to moderate intensity exercise and when ingested, it suppresses the higher relative rates of fat oxidation usually observed at exercise intensities less than 60% of VO2, max.

Adult↗

PubMed1995

The relationship between critical power and running performance.

Critical power is a theoretical concept that presumes there is a certain work-rate which may be maintained without exhaustion. The extent to which critical power predicts running performance over varying distances has not been determined, and so the aim of this study was to correlate measurements of critical power in the laboratory to running performances in the field at 40 m and 1, 10 and 21.1 km in a group of .17 male long-distance runners (mean +/- S.D. age = 31.7 +/- 7.3 years). Each subject ran to exhaustion on the treadmill in the laboratory at six different speeds, ranging from 17 to 25 km h-1. Least squares analyses were used to fit an exponential decay to the relationship between the running speed (y) versus time to exhaustion (x). Critical power was calculated as the running speed (y) coinciding with the asymptote or C parameter of the y = A.e(-Bx) + C relationship. The VO2 max was also measured in all subjects. For the data in the field, each subject was timed over 40 m and 1 km and participated in 10- and 21.1-km races. The mean critical power of the subjects in this study was 18.5 +/- 1.6 km h-1. The test-retest correlation coefficient for the determination of critical power was r = 0.99. The mean VO2 max, measured in a progressive exercise protocol starting at 13 km h-1 and increasing by 1 km h-1 every minute, was 59.2 +/- 4.6 ml O2 kg-1 min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Running intensity as determined by heart rate is the same in fast and slow runners in both the 10- and 21-km races.

The aims of this study were to determine (1) whether running speed is directly proportional to heart rate (HR) during field testing and during 10- and 21-km races, and (2) whether running intensity, as estimated from HR measurements, differs in 10- and 21-km races and between slow and fast runners at those running distances. Male runners were divided into a fast (65-80 min for 21 km; n = 8) or slow (85-110 min for 21 km; n = 8) group. They then competed in 10- and 21-km races while wearing HR monitors. All subjects also ran in a field test in which HR was measured while they ran at predetermined speeds. The 10-km time was significantly less in the fast compared with the slow group (33:15 +/- 1:42 vs 40:07 +/- 3:01 min:s; mean +/- S.D.), as was 21-km time (74:19 +/- 4:30 vs 94:13 +/- 9:54 min:s) (P < 0.01). Despite the differences in running speed, the average running intensity (%HRmax) for the fast and slow groups in the 10-km race was 90 +/- 1 vs 89 +/- 3% and in the 21-km race 91 +/- 1 vs 89 +/- 2%, respectively. In addition, %HRmax was consistently lower in the field test at the comparative average running speeds sustained in the 10-km (P < 0.01) and 21-km (P < 0.001) races. Hence, factors in addition to work rate or running speed influence the HR response during competitive racing. This finding must be considered when running intensity for competitive events is prescribed on the basis of field testing performed under non-competitive conditions in fast and slow runners.

Adult↗

PubMed1995

Nutritional practices of athletes: are they sub-optimal?

Athletes' nutritional needs are principally determined by their training load (the intensity x frequency x duration of daily workouts) and body mass. Analyses of the diets of track and field competitors and marathon runners reveal a macronutrient composition similar to that of weight-matched, inactive individuals. Male athletes generally ingest adequate dietary energy to meet their daily energy expenditure and all vitamin and mineral needs. However, the energy intake of most female athletes is less than might be anticipated based on their training load. As a result, intakes of iron, calcium, vitamin B12 and zinc are often below the recommended daily allowances. Compared with the recommendations of sports nutritionists and exercise physiologists, the majority of athletes consume a diet which might be considered significantly deficient in carbohydrate (CHO). Although there is currently little scientific support for increasing the proportion of daily energy intake from CHO above the 45-55% (approximately 5 g kg BM-1 day-1) chronically consumed by most athletes, such a regimen would probably improve an athlete's training capacity, especially when rapid recovery from intense activity is required.

Dietary Carbohydrates↗

PubMed1995

The effects of carbohydrate loading on muscle glycogen content and cycling performance.

This study compared the effects of supplementing the normal diets of 8 endurance-trained cyclists with additional carbohydrate (CHO), in the form of potato starch, for 3 days on muscle glycogen utilization and performance during a 3-hr cycle ride. On two occasions prior to the trial, the subjects ingested in random order either their normal CHO intake of 6.15 +/- 0.23 g/kg body mass/day or a high-CHO diet of 10.52 +/- 0.57 g/kg body mass/day. The trial consisted of 2 hr of cycling at approximately 75% of VO2peak with five 60-s sprints at 100% VO2peak at 20-min intervals, followed by a 60-min performance ride. Increasing CHO intake by 72 +/- 9% for 3 days prior to the trial elevated preexercise muscle glycogen contents, improved power output, and extended the distance covered in 1 hr. Muscle glycogen contents were similar at the end of the 3-hr trial, indicating a greater utilization of glycogen when subjects were CHO loaded, which may have been responsible for their improved cycling performance.

Adult↗

PubMed1995

Fatal cycling injuries.

Cycling accidents are responsible for significant morbidity and mortality, especially in boys under the age of 16. While most cycling injuries result from simple falls from the bicycle, the majority of fatalities are caused by head injuries resulting from accidents involving motor vehicles. It is estimated that up to 85% of all cycling fatalities caused by head injuries could be prevented by the use of an appropriate cycling helmet. Although the majority of adult cyclists wear helmets the reverse is true for children, who comprise the greatest proportion of all cyclists. Intensive educational programmes increase the number of cycling helmets that are sold, but have a lesser effect on the number used while cycling. Legislation, compassionately enforced on minors, i.e. with an understanding attitude towards their developmental stage, is the only proven technique that substantially improves rates of helmet use by young cyclists. Such legislation reduces their morbidity and mortality from head injuries. This article reviews the epidemiological factors associated with traumatic cycling injuries and the nature of these injuries. Special attention is paid to head injuries and the evidence that these are largely preventable with the use of appropriate 3-layered cycling helmets, the features of which are detailed. Factors promoting or discouraging helmet use by children are reviewed. These include the following factors: age, since helmet use is highest in mature cyclists and lowest in children because of negative peer pressure; parental example, including an attitude of safety consciousness and parental concern; higher levels of education; access to discounted helmets; public campaigns to promote helmet use; and, most importantly, appropriate legislation. But it is clear that appropriate legislation making helmet use compulsory for all cyclists is the only effective method for increasing helmet use, especially by young cyclist. Such legislation would reduce a mortality rate among young cyclists that has been equated to the mortality caused by some childhood infections in the pre-vaccination era. Some argue that physicians have a particular responsibility for promoting effective legislation for mandatory helmet use so that young children can be 'vaccinated' against the risk of the modern childhood epidemic; fatal head injury while cycling.

Adolescent↗

PubMed1995

Non-steroidal anti-inflammatory drugs fail to enhance healing of acute hamstring injuries treated with physiotherapy.

The effects of two non-steroidal anti-inflammatory drugs (NSAIDs), meclofenamate and diclofenac, in combination with physiotherapy modalities on the rate of healing of acute hamstring muscle tears were studied in a double-blind, placebo-controlled trial. Fourty-four of the 75 patients with this injury recruited were assessed and randomly allocated to one of three treatment groups: meclofenamate (100 mg 3 times a day), diclofenac (50 mg 3 times a day) and placebo. All patients received the same intensive physiotherapy treatment over the 7-day treatment period. Patient assessments were performed on days 1, 3 and 7 of the 7-day study period and included pain assessment (visual analogue scale), swelling measurement (thigh circumference measurement at the site of the muscle tear) and isokinetic muscle performance testing. Treatment produced a significant improvement in all measurements in all groups, but there was no difference in any measurement between groups. However, when only the more severe injuries were analysed, the reported pain score at day 7 was significantly lower in the placebo group than in either the meclofenamate group or the diclofenac group (P < 0.05). Hence this study did not find any additive effect on the healing of acute muscle injuries when meclofenamate or diclofenac was added to standard physiotherapeutic modalities. The study therefore does not support the use of NSAIDs in the treatment of acute hamstring muscle injuries.

Adult↗

PubMed1995

Bone mineral density in mature, premenopausal ultramarathon runners.

We measured bone mineral density (BMD) in 25 premenopausal ultramarathon (56 km) runners aged 29-39 yr and related risk factors for decreased BMD with actual BMD. Fifteen runners who had never had oligo/amenorrhea (R) were compared with 10 runners (OA): 4 oligomenorrheic, 2 amenorrheic, and 4 with prior oligo/amenorrhea. Menstrual, dietary and training data were obtained. BMD of the lumbar spine (LS) and proximal femur (F) were measured by dual energy x-ray densitometry. Both groups had similar body mass (58 +/- 8 vs 57 +/- 8 kg), running and dietary histories. F BMD was not different (P = 0.07) and correlated only with BMI (P < 0.05; r = 0.43). LS BMD was lower in OA (0.946 +/- 0.098 g.cm-2) than R (1.088 +/- 0.069 g.cm-2; P < 0.001). Menstrual History Index (MHI), (estimated periods.yr-1 since age 13), was higher in R (11.6 +/- 0.6) than OA (9.4 +/- 2.1; P < 0.01). LS BMD correlated with MHI (P < 0.0005; r = 0.67) and years oligomenorrheic (P < 0.01; r = -0.58) but not years amenorrheic, parity, breastfeeding, diet, or training. In conclusion, in mature women distance runners low LS BMD is related to a history of oligo/amenorrhea regardless of resumption of regular menstrual cycles in some subjects. Not only amenorrhea, but also prolonged oligomenorrhea may negatively influence peak adult bone mass.

Adult↗

PubMed1995

A lumbar body support (KBS 2000) alters lumbar muscle recruitment patterns in patients with acute-upon-chronic lower back pain.

OBJECTIVE: To determine the effects of a locally designed lumbar body support (LBS) on integrated electromyographic (IEMG) activity of the lumbar erector spinae muscles, on heart rate and on ratings of discomfort in patients with low back pain. DESIGN: Non-randomised controlled trial. SETTING: Patients referred from general practitioners and back pain rehabilitation programmes in Cape Town. PATIENTS AND OTHER PARTICIPANTS: Ten patients with low back pain of diverse causes. Values were compared with those in 10 control subjects without low back pain. INTERVENTION: Patients and controls lay supine on (in random order) either a flat conventional mattress or a LBS placed on top of the flat mattress, for a 30-minute period (acute exposure), and every night for 2 weeks (chronic exposure). MAIN OUTCOME MEASURES: IEMG activity of the lumbar erector spinae muscles, heart rate, and perception of comfort. RESULTS: IEMG activity of the lumbar erector spinae muscles did not differ between controls and patients when lying on the LBS on top of the CM after either acute or chronic exposure. However, it was significantly greater (P < 0.05) in patients than in controls when lying on the flat mattress. Subjective ratings of discomfort and heart rates mirrored these changes and were higher in patients only when lying on the flat mattress (P < 0.05). Patients with low back pain also reported that sleeping overnight on the LBS on top of their own mattress significantly reduced discomfort ratings. CONCLUSIONS: When lying on a mattress with a flat surface, patients with chronic low back pain have higher IEMG activity of the erector spinae muscles, higher heart rates and higher subjective ratings of discomfort than do control subjects. These differences disappear when both groups use a specially designed lumbar body support placed on top of the flat surface. These preliminary studies suggest that a lumbar body support should be evaluated in the chronic management of low back pain.

Adult↗

PubMed1995

Dehydration during exercise: what are the real dangers?

The belief that dehydration poses significant health risks for endurance athletes, especially marathon and ultramarathon runners, stems from the classical 1969 study of Wyndham and Strydom entitled "The Danger of an Inadequate Water Intake During Marathon Running." The subsequent influence of the paper relates more to its incorrect title than to its scientific content. For the authors did not study nor did they identify any dangers resulting from an inadequate water intake during marathon running. In fact, the most dehydrated runners in their studies were also the most successful, as they won the competitive races that were studied. The positive result of the study was to influence international rule changes to allow increased fluid intake during competitive running races. The less desirable effect was to induce a dogmatic zeal among sports medicine practitioners who began to extol the dangers of dehydration during exercise. The (il)logic spurring this zeal seems to have been the conclusion that progressive dehydration during exercise will cause heatstroke, which is the most important cause of collapse during exercise. Hence, (i) heatstroke during running can only be avoided if dehydration is prevented, and (ii) all persons who collapse in association with exercise will have a heat disorder, which must be treated with intravenous fluid therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Dehydration↗