A new respiratory valve system for measuring oxygen uptake during swimming

We describe a new respiratory valve system with minimal dead space, which allows measurement of ventilation and oxygen uptake during swimming. The device offers considerable advantages in efficiency and accuracy over current equipment, and can be used in conjunction either with a miniaturized telemetry system for oxygen uptake measurement or with a conventional system. The valve has a low airflow resistance, a small dead space (15 ml), and an electrically operating, closed-circuit pump to remove excess water from the expiratory tube. The external form and the buoyancy of the valve have been hydrostatically and hydrodynamically designed to reduce drag and to ensure a correct mass in the water. To obtain this result a very sophisticated material, carbon fibre, has been utilized. Our studies showed that this respiratory system is ideal for obtaining valid and reliable values of oxygen uptake during swimming, even at high speed and in endurance swimming tests.     

劳动复合方案对小鼠血浆心钠素和耐力的实验研究

昆明种小鼠56只，在两个海拔高度上（300m和5000m）各分为两个组（对照组和复合组），分别给予相应的处理因素后，检测其血浆ANP水平和游泳时间。结果表明，小鼠在海拔5000m生活48h后，其血浆ANP较海拔300m小鼠降低52．87％，而其游泳时间则增长91．59％；在两个海拔高度上，复合组血浆ANP都较对照组降低，而游泳时间都长于对照组．提示复合方案提高高原劳动能力的机理，可能与降低体内血浆ANP水平有关。     

Hormonal responses to training and its tapering off in competitive swimmers: relationships with performance

During a winter training season, the effects of 12 weeks of intense training and 4 weeks of tapering off (taper) on plasma hormone concentrations and competition performance were investigated in a group of highly trained swimmers (n = 8). Blood samples were collected and the swimmers performed their speciality in competition at weeks 10 (mid-season), 22 (pre-taper) and 26 (post-taper). No statistically significant changes were observed in the concentrations of total testosterone (TT), non-sex hormone binding globulin-boundtestosterone (NSBT), cortisol (C), luteinising hormone, thyroid stimulating hormone, triiodothyronine, thyroxine plasma catecholamines, creatine kinase and ammonia during training and taper. Mid-season NSBT: C ratio and the amount of training were statistically related (r = 0.82,P < 0.05). Competition performance slightly declined during intense training [0.52 (SD 2.51) %, NS] and improved during taper [2.32 (SD 1.69)%,P < 0.01]. Changes in performance during training and taper correlated with changes in ratios TT: C (r = 0.86,P < 0.01andr = 0.81,P < 0.05, respectively) and NSBT: C (r = 0.77,P < 0.05 andr = 0.76,P < 0.05, respectively). In summary, these results showed that the monitored plasma hormones and metabolic indices were unaltered by 12 weeks of intense training and 4 weeks of taper. The TT: C and NSBT: C ratios, however, appeared to be effective markers of the swimmers' performance capacities throughout the training season.     

Energy balance of human locomotion in water

In this paper a complete energy balance for water locomotion is attempted with the aim of comparing different modes of transport in the aquatic environment (swimming underwater with SCUBA diving equipment, swimming at the surface: leg kicking and front crawl, kayaking and rowing). On the basis of the values of metabolic power (Ė), of the power needed to overcome water resistance (_d) and of propelling efficiency (_P=_d/_tot, where _tot is the total mechanical power) as reported in the literature for each of these forms of locomotion, the energy cost per unit distance (C=Ė/v, where v is the velocity), the drag (performance) efficiency (_d=_d/Ė) and the overall efficiency (_o=_tot/Ė=_d/_P) were calculated. As previously found for human locomotion on land, for a given metabolic power (e.g. 0.5 kW=1.43 l·min^–1 O₂) the decrease in C (from 0.88 kJ·m^–1 in SCUBA diving to 0.22 kJ·m^–1 in rowing) is associated with an increase in the speed of locomotion (from 0.6 m·s^–1 in SCUBA diving to 2.4 m·s^–1 in rowing). At variance with locomotion on land, however, the decrease in C is associated with an increase, rather than a decrease, of the total mechanical work per unit distance (W_tot, kJ·m^–1). This is made possible by the increase of the overall efficiency of locomotion (_o=_tot/Ė=W_tot/C) from the slow speeds (and loads) of swimming to the high speeds (and loads) attainable with hulls and boats (from 0.10 in SCUBA diving to 0.29 in rowing).     

Validity of heart rate and ratings of perceived exertion as indices of exercise intensity in a group of children while swimming

Summary The purpose of this study was to investigate the validity of heart rate (f _c) and ratings of perceived exertion (RPE) as indices of exercise intensity in a group of children while swimming. Six healthy male swimmers, aged 10–12, swam tethered using the breast-stroke in a flume. The resistance started at 1.0 kg and increased in 1.0 kg steps up to the point of their exhaustion. The subjects swam for 5 min during each period, with a rest of 10–20 min until they had returned to their resting f _c level. The last exercise intensity was with the maximal mass the subjects could support for 2 min. The last min of oxygen consumption (VO₂) and 30 s of f _c were measured during each exercise period. The subjects gave their RPE assessment at the end of exercise.The individual relationships between f _c and VO₂, and percentage maximal oxygen consumption (% VO_2max, were linear with a high correlation r=0.962–0.996 and r=0.962–0.996, respectively. Therefore, it was concluded that f _c was valid as an index of the exercise intensity of children while swimming. Compared to the results found in adults using a similar protocol, the children's f _c were 8.3–26.9 beats·min^–1 higher than those of the adults at the given % VO_2max. The present study showed two different patterns in the relationship between VO₂ and RPE in individuals. In two subjects the RPE increased linearly with VO₂ while in the other four subjects the increase was discontinuous. If f _c and RPE were to be applied to the setting and evaluation of exercise intensity during swimming, it would seem that f _c would be a more useful guide than RPE for some children.     

Biochemical responses during recovery from maximal and submaximal swimming exercise

Summary We set out to demonstrate whether changes in plasma volume, haematocrit and some important blood constituents occurred after swimming 100 m and 800 m, as well as monitoring the duration of these changes. We measured exercise-induced changes in concentration of plasma constituents in eight subjects, and determined the expected effects of haemoconcentration on these constituents. We also investigated the different biochemical responses occurring after maximal exercise (100 m), as compared to submaximal exercise (800 m). The haematocrit increased significantly after the 100 m swim and to a lesser extent after the 800-m swim, returning to basal levels within 30 min. The plasma volume decreased by 16% on completion of the 100 m and by 8% on completion of the 800 m. The blood lactate concentration increased 15-fold and 10-fold after the 100-m and 800-m swims respectively. The plasma potassium concentration increased significantly immediately on completion of the 100-m swim, then decreased significantly at 2 1/2 and 5 min post-exercise, returning to near-basal values at 30 min. The potassium concentration measured after the 800-m event did not differ significantly from basal levels, however the measured concentrations were significantly lower than the concentrations expected on the basis of haemoconcentration. The plasma sodium concentrations measured after both 100-m and 800-m swims were significantly increased. However, calculations correcting for haemoconcentration showed significant losses in toal circulating sodium. Our study demonstrates marked changes in plasma volume and certain blood constituents after maximal intensity swimming, and less marked changes after submaximal exercise. We also demonstrated the importance of taking the effects of haemoconcentration into account when evaluating changes in concentration of plasma constituents.     

Cardiovascular,hormonal and body fluid changes during prolonged exercise

Summary During prolonged heavy exercise a gradual upward drift in heart rate (HR) is seen after the first 10 min of exercise. This secondary rise might be caused by a reduction in stroke volume due to reduced filling of the heart, which is dependent upon both hemodynamic pressure and blood volume. Swimming and bicycling differ with respect to hydrostatic pressure and to water loss, due to sweating. Five subjects were studied during 90 min of bicycle exercise, and swimming the leg kick of free style. The horizontal position during swimming resulted in a larger cardiac output and stroke volume. After the initial rise in heart rate the secondary rise followed parallel courses in the two situations. The rises were positively related to the measured increments in plasma catecholamine concentrations, which continued to increase as exercise progresssed. The secondary rise in HR could not be explained by changes in plasma volume or in water balance, nor by changes in plasma [K]. The plasma volume decreased 5–6% (225–250 ml) within the first 5 to 10 min of exercise both in bicycling and swimming, but thereafter remained virtually unchanged. The sweat loss during bicycling was four times greater than during swimming; but during swimming the hydrostatic conditions induced a diuresis, so that the total water loss was only 25% less than during bicycling.     

An energy balance of front crawl

With the aim of computing a complete energy balance of front crawl, the energy cost per unit distance (C= v^–1, where is the metabolic power and v is the speed) and the overall efficiency (_o=W_tot/C, where W_tot is the mechanical work per unit distance) were calculated for subjects swimming with and without fins. In aquatic locomotion W_tot is given by the sum of: (1) W_int, the internal work, which was calculated from video analysis, (2) W_d, the work to overcome hydrodynamic resistance, which was calculated from measures of active drag, and (3) W_k, calculated from measures of Froude efficiency (_F). In turn, _F=W_d/(W_d+W_k) and was calculated by modelling the arm movement as that of a paddle wheel. When swimming at speeds from 1.0 to 1.4 m s^–1, _F is about 0.5, power to overcome water resistance (active body drag × v) and power to give water kinetic energy increase from 50 to 100 W, and internal mechanical power from 10 to 30 W. In the same range of speeds increases from 600 to 1,200 W and C from 600 to 800 J m^–1. The use of fins decreases total mechanical power and C by the same amount (10–15%) so that _o (overall efficiency) is the same when swimming with or without fins [0.20 (0.03)]. The values of _o are higher than previously reported for the front crawl, essentially because of the larger values of W_tot calculated in this study. This is so because the contribution of W_int to W_tot was taken into account, and because _F was computed by also taking into account the contribution of the legs to forward propulsion.     

游泳训练大鼠血浆生物活性肽含量的变化及意义

目的研究运动性心肌肥大形成中血浆生物活性肽的含量及意义.方法wistar大鼠分为运动训练组和对照组,NPY、CGRP、ET和ANP用放射免疫方法测定,血压和心率用八道生理记录仪记录.结果(1)运动组大鼠游泳训练8周后,心脏系数比对照组增加36.8%(P＜0.05),而收缩压、舒张压、平均动脉压和心率与对照组无差异(P＞0.05);(2)运动组心肌肥大大鼠血浆NPY均比照组降低88%(P＜0.01);(3)运动组心肌肥大大鼠血浆CGRP比对照组升高31%(P＜0.01);(4)运动组血浆ET和ANP浓度与对照组无差异.结论运动性心肌肥大形成中血浆的CGRP、NPY含量变化不同,提示CGRP和NPY对运动性心肌肥大的形成可能有重要作用.