Plasma volume and blood metabolites in middle-aged runners during a warm-weather marathon

Summary Plasma volume (PV), blood-borne substrate, and electrolyte responses to a warm weather (WBGT 15.5–24.5 C) marathon race were observed in four male and two female runners averaging 48 years of age. Additionally, continuous recordings were made of heart rate (HR) in three, and of rectal temperature (T_re) in two of the men. The race was finished by three of the men, with an average time of 3.61 h, a running pace estimated to require from 60–66% of the runner's max. Near steady state levels for HR and T_re, ranging from 140–165 beats·min^–1 and from 38.5–39.3 C, respectively, were reached early in the race. Total and percentage weight losses for the finishers were 2.52 kg and 3.9%, 2.18 kg and 3.4%, 4.77 kg and 6.7%, respectively; corresponding reductions in PV for these runners were 5.4%, 13.2%, and 27.4%. Pre-race control and immediate post-race serum glucose concentrations averaged 109 and 154 mg·dl^–1 respectively. Final blood lactate values ranged from 11–42 mg·dl^–1. Thus, it may be concluded that middle-aged runners who were successful in completing the marathon in a warm environment did so while maintaining steady state levels of HR and T_re. Although only water was ingested during the race, serum glucose for the finishing runners remained above, while serum [Na⁺] and [Cl^–] remained within ±8% of, control values throughout the run. Complete data obtained from only one of the runners suggest that the initial exercise-induced reduction in PV is not augmented by subsequent cumulative dehydration provided water intake during the race is sufficient to limit weight loss to <4%.     

Marathon running: physiological and chemical changes accompanying late-race functional deterioration

Summary Twenty-one experienced runners were studied before, during and immediately after a marathon race to ascertain whether either depletion of energy substrate or rise in body temperature, or both, contribute to laterace slowing of running pace. Seven runners drank a glucose/electrolyte (GE) solution ad libitum (Na^– 21 mmol 1^–1, K⁺ 2.5 mmol l^–1, Cl^– 17 mmol l – l, PO₄ ^2– 6 mmol 1^–1, glucose 28 mmol 1^–1) throughout the race; 6 drank water and 8 drank the GE solution diluted 1:1 with water. Although average running speeds for the three groups were not significantly different during the first two-thirds (29 km) of the race, rectal temperature was significantly higher (P < 0.05) and reduction of plasma volume was greater (P <0.05) in runners who replaced sweat losses with water. During the last one-third of the race, the average running pace of the water-replacement group slowed by 37.2%; the pace slowed by 27.9% in the 8 runners who replaced their sweat loss with GE diluted 1:1 with water (1/2 GE) and 18.2% in runners who replaced fluid loss with full-strength solution (GE). Eleven runners (5 in the water group, 4 in the 1/2 GE group and 2 in the GE group) lapsed into a walk/run/walk pace during the last 6 miles of the race. Ten of these had a rectal temperature of 39° C or greater after 29 km of running, and plasma volume in these runners was reduced by more than 10%. Only 1 runner among those who ran steadily throughout the race had such an elevation of temperature and reduction of plasma volume. A significant reduction in plasma glucose concentration (less than 3.3 mmol 1^–1) was present in 5 of the 11 walk/run/walk subjects and in none of those who ran steadily. The results are consistent with the suggestion that assumption of the walk/run/walk pace resulted from high body temperature associated with either diminished plasma volume or low blood sugar.     

β-Endorphin and adrenocorticotrophin after incremental exercise and marathon running-female responses

Investigations of exercise-induced increases in -endorphin, adrenocorticotropic hormone (ACTH) and cortisol concentration have been carried out mainly in men. Data concerning the female reaction are sparse and less clear. In a comparison between incremental exercise and marathon running 14 experienced female marathon runners volunteered to run to exhaustion according to an incremental treadmill protocol. They ran a marathon 4 weeks later. Blood was analysed for -endorphin, ACTH and cortisol concentration immediately prior to the laboratory treadmill test, 3, 30 and 60 min later, as well as prior to the marathon, after 60 min and 120 min of running and 3, 30 min, and 24 h after completion of the run. At each blood collection, lactate concentration, heart frequency and perceived exertion were determined. The mean marathon running time was 3.22 h. Baseline concentrations for -endorphin of 22 pmol · l^–1 before the marathon and 19 pmol · l^–1 before the treadmill exercise increased 1.4-fold 30 min after the marathon and 1.9-fold after the treadmill exercise; for ACTH the baseline of 4.7 and 4.0 pmol · l^–1 t was increased by 8.3- and 10.3-fold, respectively. Cortisol concentration rose exponentially from a baseline 17 g · dl^–1 and peaked at 2.2-fold 30 min after the run, when the maximal concentration also had been reached after the treadmill test, increasing 1.3-fold from a baseline of 21 g · dl^–1. The maximal values for cortisol concentration after both exercises differed from each other, while the maxima of ACTH and -endorphin concentrations were similar. The ACTH and -endorphin concentration declined more slowly during the recovery after the marathon than after the treadmill. Cortisol concentration was below baseline 24 h later. In comparison with men studied earlier, female marathon runners showed higher baseline concentrations and lesser increases in -endorphin and lower baseline concentrations and larger increases in ACTH concentration after both types of exercise. The delayed decrease in concentration of the hormones after the marathon was similar in male and female runners.     

国际马拉松伤病员救治实践分析

目的探讨国际马拉松比赛的医疗急救保障工作,为以后类似急救保障提供经验参考。方法回顾分析2010杭州国际马拉松竞赛医疗急救保障过程中受伤运动员的受伤特点、急救保障计划与实施情况。结果马拉松竞赛受伤人群多为青年男性,以运动损伤为主,以到达终点后发病为多,所有受伤人员均得到及时、合理有效的医疗救治。结论赛前合理预案的制定、结构合理的医疗团队以及与其他各部门团队间的有力协调是保障竞赛运动员生命安全、顺利完成马拉松竞赛的关键。     

The age of the best ultramarathon performance – the case of the “Comrades Marathon”

The aim of the present study was to determine the age of the fastest running speed in 202,370 runners (34,090 women and 168,280 men) competing in the “Comrades Marathon” between 1994 and 2015 using non-linear regression analysis (second order polynomial function). When all runners were considered in 1-year age intervals, the fastest running speed (9.61 ± 1.65 km/h) was achieved at the age of 29.89 years in men, whereas women achieved it at the age of 35.96 years 8.60 ± 1.10 km/h. When the fastest runners were considered in 1-year intervals, the fastest running speed (16.65 km/h) was achieved in men at the age of 36.38 years. For the fastest women, the age of the fastest running speed (13.89 km/h) was 32.75 years. To summarize, for all runners, men achieved the best ultramarathon performance ~6 years earlier than women. When the fastest runners were considered, however, men achieved the best performance ~4 years later than women.     

Post-marathon Paradox in IDDM: Unchanged Insulin Sensitivity in Spite of Glycogen Depletion

Acute physical exercise usually enhances insulin sensitivity. We examined the effect of a competitive 42 km marathon run on glucose uptake and lipid oxidation in 7 runners with insulin-dependent diabetes mellitus (IDDM), aged 36 ± 3 yr, BMI 23.9 ± 0.5 kg m⁻², VO_{2 max} 46 ± 1 ml kg⁻¹ min⁻¹, HbA_1c 7.7 ± 0.3 %, duration of diabetes 16 ± 5 yr, runtime 3 h 47 ± 8 min. On the marathon day, they reduced pre-race insulin doses by 26 ± 8 %, and ingested 130 ± 33 g carbohydrate before, 91 ± 26 g during, and 115 ± 20 g after the race. During the run, blood glucose concentration fell from 14.4 ± 2.0 to 7.4 ± 3.0 mmol l⁻¹ (p < 0.05) and serum insulin from 51 ± 8 to 33 ± 8 pmol l⁻¹ (p < 0.05). Serum NEFA increased by 4-fold (p < 0.05), but fell to the normal level by next morning. Muscle glycogen content was 56 % lower (p < 0.05) and glycogen synthase fractional activity 40 % greater (p < 0.05) in the morning after the marathon as compared to the resting control day. In spite of glycogen depletion, whole body glucose disposal (euglycaemic insulin clamp) was unchanged, while glucose oxidation (indirect calorimetry) was decreased by 49 % (p < 0.05) and lipid oxidation increased by 41 % (p < 0.01). There was an inverse correlation between the rates of lipid oxidation and glucose uptake after the marathon (r = −0.75; p < 0.05). In conclusion: after successfully managed marathon running in patients with IDDM, insulin sensitivity was not increased in spite of low glycogen content and enhanced glycogen synthase activity after marathon, probably because of increased lipid oxidation. © 1997 by John Wiley & Sons, Ltd.     

平板运动试验对马拉松运动成绩的估测意义

目的 探讨平板运动试验对马拉松运动时间的预测性。方法 纳入2016年10月~2017年1月参与正规公路马拉松全程、半程及10km赛事的业余运动员172例,赛前2~4周进行平板运动试验,并要求受试者运动至体力耗竭。分析试验数据与完赛时间的相关性。结果 各组的试验总运动时间、最大速度及坡度、运动终止达到的级数和累计代谢当量均与完赛时间呈负相关（P<0.01）。全程马拉松组中的年龄与完赛时间表现呈负相关（P<0.01）,并且不同年龄显示出试验对成绩预测性的差异。全程马拉松和10km马拉松组恢复期1min末心率自峰值下降比与完赛时间呈负相关（P<0.05）。结论 平板运动试验作为马拉松运动员赛前心脏风险的有效筛查手段,同样对心脏耐力水平和运动成绩有评估价值。     

马拉松运动的心脏风险、猝死及防范策略

马拉松运动是一项具有挑战性的运动项目，对人体心脏有着巨大影响。本文依据国内外研究，全面综述马拉松与心律失常、心肌纤维化、冠状动脉钙化的关系，深入分析马拉松猝死的现状和特点。最后，对如何规避马拉松赛场意外提出了三级预防策略。