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Endurance performance is impaired in the heat, and a combination of high temperature and high humidity presents a major challenge to the elite marathon runner, who must sustain a high metabolic rate throughout the race. The optimum temperature for marathon performance is generally about 10-12 °C. The optimum temperature may be lower for faster runners than for slower runners. Sweat evaporation limits the rise in core temperature, but dehydration will impair cardiovascular function, leading to a fall in blood flow to muscle, skin and other tissues. There is growing evidence that the effects of high ambient temperature and dehydration on performance of exercise may be mediated by effects on the central nervous system. This seems to involve serotonergic and dopaminergic functions., (© 2010 John Wiley & Sons A/S.)

Objective: To examine the influence of a seven day diet manipulation on performance during a 10 km treadmill time trial in trained runners., Methods: Six trained runners ran two 10 km time trials on a treadmill set at a constant 4% gradient, each after a 7 d period of dietary manipulation. The two experimental diets were a low carbohydrate (CHO) diet (40% CHO by total energy) to be consumed for 7 d, and a high CHO diet containing 55% CHO for the first 4 d followed by 70% CHO for the remaining 3 d. Blood samples were obtained before and immediately after each run. Expired gases were collected and heart rate monitored., Results: Performance time following the high CHO [48.6(SD 2.7) min] and low CHO [48.6(2.3) min] diets was not different (P = 0.72), nor were there any differences in running speed between conditions. No significant differences were found between conditions in any of the metabolites measured (blood lactate, glucose, glycerol, and plasma free fatty acids). The rate of CHO oxidation was greater on the high CHO diet compared to the low CHO diet (P < 0.05). Heart rate was not different between conditions., Conclusions: The results of this study indicate that moderate changes in the composition of the diet do not affect 10 km running performance in trained subjects.

Blood biochemical indices of iron status were measured in venous blood from 20 runners and 6 control subjects. All subjects were male, ages 20 to 40 years, and stable with regard to body weight and degree of physical activity. Dietary analysis was undertaken using a 7-day weighed food intake. There was no evidence of iron deficiency: hemoglobin concentrations and serum ferritin levels were within the normal population range for all individuals. However, serum ferritin was negatively correlated with the amount of training. Daily iron intake appeared to be adequate; iron intake was correlated with protein intake but not related to training or energy intake. Serum ferritin, an indicator of iron status, was significantly correlated with vitamin C intake but not iron intake. Serum transferrin concentration was higher in the group of athletes undertaking a high weekly training load compared with the control subjects, suggesting an alteration in iron metabolism although there was no evidence of increased erythropoiesis. The biological significance of this is unclear.

1. Blood antioxidants were measured in venous blood samples from 20 runners and six sedentary individuals. All subjects were male, between 20 and 40 years old, and in steady state with respect to body weight and physical activity patterns. Dietary analysis was undertaken using a 7-day weighed food intake. Correlations were sought between antioxidants in blood and (1) weekly training distance and (2) maximum oxygen uptake. In addition, 12 runners could be classified into two groups undertaking either low (range 16-43 km, n = 6) or high (80-147 km, n = 6) weekly training. 2. Body weight (range 55.3-90.0 kg) and percentage body fat (range 7-19%) both showed negative correlations with the weekly training distance (both P less than 0.001). Energy intake and maximum oxygen uptake were both correlated with the weekly training distance (both P less than 0.001). 3. Plasma creatine kinase activity, an indicator of muscle damage, was significantly correlated with the weekly training distance (P less than 0.01), whereas the plasma concentration of thiobarbituric acid-reactive substances, an indicator of free-radical-mediated lipid peroxidation, decreased with increased maximum oxygen uptake (P less than 0.01). 4. Erythrocyte alpha-tocopherol content was greater in the two running groups (P less than 0.05) compared with the sedentary group, and lymphocyte ascorbic acid concentration was significantly elevated in the high-training group (P less than 0.01) compared with the low-training group. 5. Erythrocyte activities of the antioxidant enzymes, glutathione peroxidase and catalase, were significantly and positively correlated with the weekly training distance (P less than 0.01 and P less than 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between prolonged exercise, oxidative stress, and the protective capacity of the antioxidant defense system has been determined. Venous blood samples were removed from seven trained athletes before and up to 120 h after completion of a half-marathon for measurements of blood antioxidants, antioxidant enzymes, and indices of lipid peroxidation. Plasma creatine kinase (CK) activity, an index of muscle damage, increased (P less than 0.05) to a maximum 24 h after the race but this was not accompanied by changes in conjugated dienes and thiobarbituric acid reactive substances (TBARS), which are indices of lipid peroxidation. An increase (P less than 0.05) in plasma cholesterol concentration (4%) immediately after the race was similar to the change in plasma volume (6%). However, transient increases (P less than 0.05) immediately postrace in the plasma concentrations of uric acid (24%), vitamin A (18%), and vitamin C (34%) were only partly accounted for by the fluid shifts. The immediate postrace increases in alpha- and gamma-tocopherol did not attain statistical significance. Erythrocyte antioxidant enzyme activities were unaffected by the exercise but the alpha- and gamma-tocopherol concentrations progressively increased (P less than 0.001 and P less than 0.05, respectively) up to 48 h postrace. Paradoxically, 24 h after the race erythrocyte susceptibility to in vitro peroxidation was markedly elevated (P less than 0.01). This enhanced susceptibility to peroxidation was maintained even at 120 h postrace and did not correspond to changes in the age of the red cell population. A decrease (P less than 0.001) in total erythrocyte glutathione immediately after the half-marathon was mainly due to a reduction in the reduced form (GSH). The results show that when trained athletes run a comparatively short distance sufficient to result in some degree of muscle damage but which is insufficient to cause elevations in plasma indices of lipid peroxidation, significant alterations in erythrocyte antioxidant status do occur.

Thirty-two volunteers participated in a two-period crossover study in which ibuprofen was tested against an identical placebo for its effectiveness in reducing muscle soreness and damage after two bouts of downhill running. Subjective soreness, quadriceps isometric strength and isometric endurance time at 50 percent of maximum strength, serum activities of creatine kinase, lactate dehydrogenase and aspartate transaminase and serum levels of creatinine and urea were recorded at intervals up to 72 hours after exercise. Each downhill run produced muscle soreness, and a decline in muscle strength and 50 percent endurance time, although these parameters were unaffected by ibuprofen treatment. All serum parameters measured increased after both runs, but for the three enzymes this increase was smaller after the second run. Serum creatine kinase and urea levels were higher in the ibuprofen group after both runs. These results indicate that ibuprofen is not an appropriate treatment for delayed onset muscle soreness and damage.

The effects of a competitive marathon race on serum biochemical and haematological parameters have been evaluated. Blood samples were obtained shortly before and immediately after the race; urine samples were also obtained before and after the race. Body weight was recorded pre- and post-race. During the race subjects consumed a total of 1.41 of either water or a dilute glucose-electrolyte solution. The average weight loss of the runners was 2.09 +/- 0.77 kg (mean +/- SD), corresponding to 2.9 +/- 0.8% of body weight. Small but significant increases in both haematocrit and haemoglobin concentration occurred; plasma volume was calculated to decrease by 4.7%. Serum potassium concentration showed no change, but the response was highly variable; serum sodium concentration increased in line with the decrease in plasma volume. In the group of subjects drinking water during the race, the pre-race plasma glucose concentration was 5.3 +/- 1.2 mmol . l-1, this was unchanged after the race (5.0 +/- 1.2 mmol . l-1). A significant increase (P less than 0.01) in the plasma glucose concentration, from 5.2 +/- 0.6 to 6.0 +/- 1.5 mmol . l-1 occurred in the group of subjects drinking the glucose-electrolyte solution. Apart from this, there were no significant differences between the two groups.

The acute effects of running a 42.2 km marathon race on the concentration and composition of the plasma lipoproteins were studied in 56 men of varying fitness, training experience, age and physical characteristics. There was no change in the mean concentration of total serum cholesterol, but a 10.9% increase (P less than 0.001) in the mean concentrations of high-density lipoprotein cholesterol (HDL-TC), representing an 11.1% increase (P less than 0.001) in the cholesteryl ester (CE) and 9.9% increase (P less than 0.001) in the unesterified cholesterol (UC) moieties of HDL. The ratio of total serum cholesterol to HDL-TC decreased significantly (P less than 0.001) during the exercise. Changes in lipoprotein concentrations during the marathon varied considerably between individual subjects, with a small proportion of subjects exhibiting relatively large increases or decreases in HDL-TC, HDL-CE and HDL-UC. Small sub-populations of runners were identified who showed abnormally large decreases in HDL-UC and abnormally small increases in HDL-CE relative to HDL-UC. A correlation (P less than 0.05) was found between the average weekly mileage of training and the increase in HDL-TC, whilst faster runners (finishing time less than 3 h; n = 13) had a significantly greater (P less than 0.02) increase in HDL-TC than slower runners (greater than 4 h; n = 14).(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of this longitudinal questionnaire study was to investigate the effects of participation or non participation in a marathon race on future running behaviour. The majority (70 per cent) of the participants who intended to run a future marathon actually did so and only 11 per cent stopped running altogether. Fewer of the pre-race drop-outs (31 per cent) who indicated their intention to run a future marathon actually did so (P less than 0.001) and more of them (24 per cent) stopped running altogether (P less than 0.001) compared with the runners in the finishers' sample. These results suggest that the experience of running in a marathon does not negatively influence future running habits. However, failure to run in a race for which an entry has been made may lead to a reduced involvement in running. The present study also examined the reasons for pre-race drop-out. Injury (36 per cent), lack of training (31 per cent) and illness (12 per cent) were the most frequently given reasons for drop-out. Few differences were found between the pre-race drop-outs and the finishers, but the drop-outs did feel that running was less important (P less than 0.001), reported a greater number of longer term injuries (P less than 0.001) and did significantly less training (P less than 0.001) than the finishers.

This study examines the reasons given for non-participation in the 1984 Aberdeen Milk Marathon by those people who entered for the race but did not run. The major reason was found to be injury during training. The future running plans of the sample were also investigated and it was found that the vast majority aimed to continue marathon running. Around two-thirds of the sample had decided not to run at least two weeks before the day of the race. A third of the respondents indicated that they would have taken part in the race had there been a half marathon option.

The red cell population in peripheral venous blood was characterised in 7 young males before and up to 16 days after a 21.1 km road race. There was a 1.9 +/- 2.4% (mean +/- SD) reduction in plasma volume immediately post race (p less than 0.05), an increase in serum osmolality from 277 +/- 4 mOsm.kg-1 to 291 +/- 14 mOsm.kg-1 (p less than 0.05) and a reduction in red cell water (64.4 +/- 0.3% to 63.4 +/- 0.4%, p less than 0.001). The latter was consistent with alterations in the manually derived MCV and MCHC values although the same Coulter derived values were unaltered. A concomitant increase in median red cell density in whole blood (1.1045 +/- 0.0009 g.ml-1 pre race to 1.1057 +/- 0.012 g.ml-1 immediate post race, p less than 0.05) was recorded by centrifugation through phthalate esters of different density. The changes in creatine content of the red cells suggested that during the race younger cells were released into the circulation but that 24 h to 72 h after the race the mean red cell age had increased. Similarly, fractionation of the red cells on discontinuous Percoll density gradients indicated that the cell population was significantly denser in all post race samples up to 72 h but had normalized by a 16 day sample; the osmotic fragility was similarly affected.(ABSTRACT TRUNCATED AT 250 WORDS)

The physiology of marathon running has been extensively studied both in the laboratory and in the field, but these investigations have been confined to elite competitors. In the present study 28 competitors who took part in a marathon race (42.2 km) have been studied; 18 male subjects recorded times from 2 h 19 min 58 s to 4 h 53 min 23 s; 10 female subjects recorded times between 2 h 53 min 4 s and 5 h 16 min 1 s. Subjects visited the laboratory 2-3 weeks after the race and ran on a motor driven treadmill at a series of speeds and inclines; oxygen uptake (VO2) was measured during running at average marathon racing pace. Maximum oxygen uptake (VO2 max) was measured during uphill running. For both males (r = 0.88) and females (r = 0.63), linear relationships were found to exist between marathon performance and aerobic capacity. Similarly, the fraction of VO2 max which was sustained throughout the race was significantly correlated with performance for both male (r = 0.74) and female (r = 0.73) runners. The fastest runners were running at a speed requiring approximately 75% of VO2 max; for the slowest runners, the work load corresponded to approximately 60% of VO2 max. Correction of these estimates for the additional effort involved in overcoming air resistance, and in running on uneven terrain will substantially increase the oxygen requirement for the faster runners, while having a much smaller effect on the work rate of the slowest competitors. Five minutes of treadmill running at average racing pace at zero gradient did not result in marked elevation of the blood lactate concentration in any of the subjects.

Rectal temperature was measured in 62 male runners who competed in the 1983 Dundee marathon race: all measurements were made immediately after the race. Competitors' times were noted at 5, 10, 15 and 20 miles (8.0, 16.1, 24.1, 32.2 km) and at the finish (26.2 miles, 42.2 km). Mean finishing time of the group was 3 hr 33 min +/- 48 min (mean +/- S.D.; range = 2 hr 17 min-5 hr 11 min). Mean running speed of the group decreased progressively as the distance covered increased. Mean post-race rectal temperature was 38.7 +/- 0.9 degrees C (range 35.6-40.3 degrees C). The post-race temperature was correlated (p less than 0.01) with the time taken to cover the last 6.2 miles (10 km) of the race, but not with the overall finishing time (p greater than 0.05). Only the fastest runners were able to maintain an approximately constant pace throughout the race, whereas the slower runners slowed down progressively. The runners with the highest post-race temperature, although not necessarily the fastest runners, also tended to maintain a steady pace throughout. The runners with the lowest post-race temperature slowed down markedly only over the last 6.2 mile section of the race. The results clearly indicate that runners forced by fatigue or injury to slow down in the latter stages of races held at low ambient temperatures may already be hypothermic or at serious risk of hypothermia.

The 1982 Aberdeen marathon race was held on a cool (12 degrees C) day on a flat, fast course. Fifty-nine of the 750 runners volunteered to take part in this study: rectal temperature of these competitors was measured within 5 min of completing the race. Venous blood samples were obtained before and immediately after the race; body weight of these subjects was also recorded before and after the race. During the race, 200 ml of fluid, either water or a glucose/electrolyte drink, was consumed at each of the seven feeding stations. The mean finishing time of the subjects was 221 +/- 37 min (mean +/- SD, range = 144-307 min). Post-race rectal temperature was 38.3 +/- 0.9 degrees C with a range of values from 35.6 degrees to 39.8 degrees C. The net weight loss was 2.02 +/- 0.72 kg equivalent to 2.9% +/- 0.8% of body weight. The correlation between post-race rectal temperature and finishing time (r = -0.234) was not statistically significant; post-race rectal temperature was significantly correlated with the time taken to complete the second half of the race (r = -0.348, P less than 0.01). No cases of heat illness were seen among the competitors. The results suggest that hypothermia rather than hyperthermia may be a problem for marathon runners competing under these conditions.

Exercise-induced muscle cramp has been considered to result from disturbances of fluid and electrolyte balance resulting from excessive sweat loss. Serum biochemical and haematological measurements were made on 82 male marathon runners before and after a 42.2-km race. Fifteen (18%) of the runners reported an attack of muscle cramp which occurred after 35 +/- 6 km (mean +/- S.D.) had been covered. These subjects were not different from the others in terms of racing performance or training status. Serum electrolyte concentrations, including sodium and potassium, were not different between those suffering from cramp and those not so affected either before or after the race, although a significant (P less than 0.001) increase in serum sodium concentrations occurred in both groups. Serum bicarbonate concentrations fell to the same extent (from 28 to 24 mmol l-1) in both groups. Significant decreases in plasma volume, calculated from the changes in circulating haemoglobin and haematocrit, occurred in both groups of subjects, but there was no difference in the extent of the haemoconcentration. The results suggest that exercise-induced muscle cramp may not be associated with gross disturbances of fluid and electrolyte balance.

A questionnaire was sent to all 960 entrants in a major city marathon race to obtain information on training-related injuries. A total of 497 replies were received; of these 287 (58%) had incurred some form of injury during preparation for the race. Seventy-one of these individuals reported more than one injury. Almost all injuries affected the lower limb, with 113 cases (32%) involving pain or disability in the knee. More than half the injured runners (158, 55%) sought no professional advice; approximately half (146, 51%) received no treatment other than rest, which was not generally considered a form of therapy. Only 18 runners (6%) reported no improvement in their condition, while 143 individuals (51%) reported a full recovery. Injury incurred during training was thought by 98 runners (35%) to have had an adverse effect on their racing performance. These results suggest that runners preparing to compete in marathon races can expect their training to be interrupted by injury.

The acute effect of running a 42.2 km marathon race on plasma lipoproteins was investigated in 12 female subjects (aged 21 to 41 years). During the race there was a significant increase (P less than 0.01) in the concentration of total plasma cholesterol. The mean post-race concentration of high density lipoprotein cholesterol (HDL-C) was 64.0 +/- 16.2 (SD) mg 100 ml-1, compared with 52.1 +/- 14.0 mg 100 ml-1 before the race, representing a significant increase (P less than 0.002). There was no significant difference in the concentration of very low density lipoprotein (VLDL) or low density lipoprotein (LDL) before and after the exercise. The mean concentration of the cholesteryl ester moiety of the HDL increased from 43.7 +/- 12.3 to 54.3 +/- 15.7 mg 100 ml-1 (P less than 0.002), while there was no significant changes in the concentration of the unesterified cholesterol, phospholipid, triacylglycerol or protein moieties of the HDL. The relative proportions of apolipoproteins A-I, A-II, C and E remained unchanged during the exercise. The changes in the concentration of each of the lipoprotein fractions observed during the marathon varied considerably between subjects. The individual increases in the concentration of HDL-C ranged from 4.1 to 28.4 mg 100 ml-1, while both increases and decreases in individual concentrations of VLDL and LDL as well as of total plasma cholesterol were observed. These observations suggest that women undergo greater changes in HDL-C concentration that men during acute exercise, while considerable variation between individuals occurs.

Twenty untrained male volunteers were required to run downhill for 45 minutes on a motor driven treadmill to induce muscle soreness. The volunteers took diclofenac or placebo before and for 72 hours after two runs 10 weeks apart, in a randomised double blind crossover design. Subjective soreness was assessed before and at intervals up to 72 hours after each run; venous blood samples, collected at the same time intervals, were used to estimate serum activities of creatine kinase, lactate dehydrogenase and aspartate aminotransferase and serum concentrations of creatinine and urea. Subjective soreness and the biochemical parameters increased after both runs, although the serum enzyme response to the second run was reduced. Diclofenac had no influence on the serum biochemical response to downhill running. Although overall soreness was not affected by diclofenac, individual soreness measurements were reduced by diclofenac at the first period of the study. These results suggest that diclofenac does not influence muscle damage, but may slightly reduce the associated soreness.

Indices of fluid loss have been compared in 47 male runners who completed a competitive marathon (42.2 km) race in times varying from 2 hr 37 min to 4 hr 51 min. Body weight was recorded before and after the race; venous blood samples were collected shortly before and immediately after the race and used for the estimation of haemoglobin concentration, packed cell volume and serum concentration of albumin and total protein. All runners drank a total of 1.4 L of water during the race. The mean decrease in body weight was 2.1 +/- 0.8 kg (mean +/- SD), corresponding to 3.0 +/- 1.1% of initial weight. The decrease in plasma volume (PV), calculated from the haematological parameters, was 6.5 +/- 7.8% (P less than 0.001). Serum total protein concentration increased (P less than 0.001) by 10.4 +/- 4.8% and serum albumin (P less than 0.001) by 9.6 +/- 5.6%. The increase in serum protein concentration was correlated (r = 0.64, P less than 0.001) with the calculated decrease in PV, but was greater (P less than 0.001) than could be accounted for by the loss of plasma water. The change in PV varied widely between individuals and was unrelated to running speed. The estimated decrease in total body water (5%) was not different from the decrease in PV (6.5%), suggesting that water losses were evenly distributed between the intracellular and extracellular compartments.

Coulter profiles with differential white cell counts, serum ferritin, and haptoglobin levels were determined in venous blood samples obtained from 90 males (M) and 25 females (F) immediately before and after completion of a competitive marathon (42.2 km) race. In an additional 20 male runners, the same measurements were performed serially during the 24 h following their completion of the race. In the pre-race samples from 90 M and 25 F, hypoferritinemia was present in 4/22 M and 1 F found to be mildly anemic. Neutropenia was detected in 4 M and 3 F and mild thrombocytopenia in 2 M. Haptoglobin levels were normal in all the female runners but reduced (less than 0.3 g/l) in 6 M. All post-race samples (88 M and 25 F) were characterized by a reactive neutrophilia and thrombocytosis including those with pre-race neutropenia or thrombocytopenia. An unexpected and incompletely explained sex difference in packed cell volume (PCV) response was observed. In males, the mean PCV increased from 0.425 +/- 0.021 to 0.444 +/- 0.028 (P less than 0.0001) whereas in females it decreased from 0.437 +/- 0.029 to 0.423 +/- 0.036 (P less than 0.05). In the post-race samples, anhaptoglobinemia was found in 13/88 M and 4/25 F. In the 20 male runners studied serially for 24 h after the race, the major changes involved a progressive increase in mean plasma volume (17.4% +/- 12.2% at 24 h) compared with the pre-race value, a progressive and significant increase in MCH and MCHC probably indicating a loss in red cell water and the gradual reversion of the reactive neutrophilia and thrombocytosis to basal levels.

A twelve parameter blood cell profile has been measured in 6 subjects before and after each phase of triathlon event. This involved 29 miles cycling, 12 miles running and finally 18.5 miles canoeing. There was a significant decrease in plasma volume (8.7% +/- 3.1%, p less than 0.001) following the first phase (cycling); this decrease was sustained to the end of the event. A substantial increase in the number of circulating leukocytes after cycling (84 +/- 58%) and running (255 +/- 83% of pre-event value) was observed. There was no further leucocyte increment after the canoeing stage which may indicate that the circulating concentration of these cells was maximal after running. Fluid shifts following the postural alteration accompanying the different types of exercise and subject variability may have masked any subtle changes in the red cell parameters.