-6°头低位卧床7 d中人的体温变化

目的观察 - 6°头低位卧床 (HDBR)模拟失重对人体体温的影响。方法记录并分析 18名健康男性青年 ( 18～ 2 2岁 ) 7d卧床期间每日早晨 ( 6∶0 0 )、下午 ( 16∶0 0 )、晚上 ( 2 0∶0 0 )的体温变化。结果人体在早晨的直肠温度 (Tre)随着卧床时间延长而逐渐降低 :卧床第 4天 (BR4d)后显著低于卧床前对照值 36.5 0± 0 .0 3℃ ,卧床第 7天 (BR7d)时降至 36.38± 0 .0 4℃ ;下午、晚上Tre分别在BR5d、BR1d后显著升高。早晨人体的平均皮肤温度 (Tsk)从BR2d起显著高于对照值 ,卧床第 7天时ΔTsk为 0 .38± 0 .14℃ ;下午、晚上的Tsk分别在BR4d、BR2d起显著升高。早晨的前额皮温 (Tforehead)有升高趋势 ;下午、晚上的Tforehead分别从BR7d、BR6d起显著高于对照值。结论卧床模拟失重可引起体温改变 :每日测量时刻和卧床时间 (d)均对Tre、Tsk、Tforehead有非常显著的影响 (P <0 .0 1)。结果提示 :人的体温节律、卧床引起的体液头向分布和体液丧失、低动力等因素 ,对卧床时人的热调节有影响     

Diurnal evolution of cycling biomechanical parameters during a 60‐s Wingate test

The purpose of this study was to assess the evolution of pedaling kinetics and kinematics during a short‐term fatigue cycling exercise at two times of day. Twenty active male subjects were asked to perform a 60‐s Wingate test against a constant braking resistance during two experimental sessions at 06:00 and 18:00 hours, i.e., very close to the hours of core temperature values, which are, respectively, the lowest and the highest. The results showed that the fatigue index was higher (P<0.05) at 18:00 hours (71.4%) than at 06:00 hours (69.2%) and power output was higher (P<0.05) in the evening than in the morning during the first 20 s of the test, after which no difference was observed. Taken together, these results showed a greater progression of fatigue in the evening than in the morning. The diurnal variations in performance and fatigue were associated (P<0.001) with diurnal changes in cycling kinematic parameters, characterized by a reduction in the range of motion of the ankle angle in the evening. These findings show that a time‐of‐day effect on movement patterns occurs during an anaerobic cycling exercise and that this phenomenon has a direct influence on performance and fatigue.     

Listening to music affects diurnal variation in muscle power output

The purpose of this investigation was to assess the effects of listening to music while warming-up on the diurnal variations of power output during the Wingate test. 12 physical education students underwent four Wingate tests at 07:00 and 17:00 h, after 10 min of warm-up with and without listening to music. The warm-up consisted of 10 min of pedalling at a constant pace of 60 rpm against a light load of 1 kg. During the Wingate test, peak and mean power were measured. The main finding was that peak and mean power improved from morning to afternoon after no music warm-up (p<0.001 and p<0.01, respectively). These diurnal variations disappeared for mean power and persisted with an attenuated morning-evening difference (p<0.05) for peak power after music warm-up. Moreover, peak and mean power were significantly higher after music than no music warm-up during the two times of testing. Thus, as it is a legal method and an additional aid, music should be used during warm-up before performing activities requiring powerful lower limbs' muscles contractions, especially in the morning competitive events.     

Cerebrovascular responses during rowing: Do circadian rhythms explain morning and afternoon performance differences?

The purpose of this study was to characterize cerebrovascular responses to rowing exercise, investigating whether their diurnal variation might explain performance differences across a day. Twelve male rowers completed incremental rowing exercise and a 2000‐m ergometer time trial at 07:00 h and 16:00 h, 1 week apart, while middle cerebral artery velocity (MCAv), cerebral (prefrontal), and muscular (vastus lateralis) tissue oxygenation and hemoglobin volume (via near‐infrared spectroscopy), heart rate, and pressure of end‐tidal CO₂ (P_ETCO₂) were recorded. MCAv was 20–25% above resting levels (68 ± 12 cm/s) during submaximal and maximal exercise intensities, despite P_ETCO₂ being reduced during maximal efforts (down ～ 0.5–0.8 kPa); thus revealing a different perfusion profile to the inverted‐U observed in other exercise modes. The afternoon time trial was 3.4 s faster (95% confidence interval 0.9–5.8 s) and mean power output 3.2% higher (337 vs 347 W; P = 0.04), in conjunction with similar exercise‐induced elevations in MCAv (P = 0.60) and reductions in cerebral oxygenation (TOI) (P = 0.12). At the muscle, afternoon trials involved similar oxygen extraction (HHb volume and TOI) albeit from a relatively lower total Hb volume (P < 0.01). In conclusion, rowing performance was better in the afternoon, but not in conjunction with differences in MCAv or exercise‐induced differences in cerebral oxygenation.     

Warm-up affects diurnal variation in power output

The purpose of this study was to examine whether time of day variations in power output can be accounted for by the diurnal fluctuations existent in body temperature. 8 recreationally trained males (29.8±5.2 yrs; 178.3±5.2 cm; 80.3±6.5 kg) were assessed on 4 occasions following a: (a) control warm-up at 8.00 am; (b) control warm-up at 4.00 pm; (c) extended warm-up at 8.00 am; and, (d) extended warm-up at 4.00 pm. The control warm-up consisted of dynamic exercises and practice jumps. The extended warm-up incorporated a 20 min general warm-up on a stationary bike prior to completion of the control warm-up, resulting in a whole body temperature increase of 0.3±0.2°C. Kinetic and kinematic variables were measured using a linear optical encoder attached to a barbell during 6 loaded counter-movement jumps. Results were 2-6% higher in the afternoon control condition than morning control condition. No substantial performance differences were observed between the extended morning condition and afternoon control condition where body temperatures were similar. Results indicate that diurnal variation in whole body temperature may explain diurnal performance differences in explosive power output and associated variables. It is suggested that warm-up protocols designed to increase body temperature are beneficial in reducing diurnal differences in jump performance.     

Time of day influences the environmental effects on muscle force and contractility

PURPOSE: To investigate the effects of environmental temperature and the diurnal increase in body temperature on muscle contractile processes, 11 male subjects performed maximal and submaximal isometric contractions of the knee extensors with recording of the electromyographic activity in four different conditions (morning/neutral, morning/moderately warm and humid, afternoon/neutral, and afternoon/moderately warm and humid). METHODS: The morning experiments were conducted between 0700 and 1900 h, and the afternoon experiments were conducted between 0500 and 0700 h. The mean laboratory temperatures and humidity were 20.5 (+/-1) degrees C + 67 (+/-4)% and 29.5 (+/-0.8) degrees C + 74 (+/-10)% for the neutral and moderately warm and humid conditions, respectively. RESULTS: Results showed a significant diurnal increase in both rectal and skin temperatures whatever the environmental conditions, and an increase in the skin temperature after a 60-min moderately warm exposure. The major finding of this study was an interaction effect of time of day and environmental conditions on the force/electromyographic activity ratio. That suggests that skeletal muscle contractility was differently increased by the passive warm-up effect of a moderately warm exposure, depending on the diurnal variation in body temperature. This conclusion is supported by an increase in force in the morning only after a 60-min warm exposure (+19%) and in a neutral environment only with the diurnal increase in body temperature (+12%). CONCLUSION: In summary, our data showed that both the warm exposure and the diurnal increase in body temperature influence muscle contractility and consequently muscle strength. However, the improvement in muscle contractility after these two passive warm-ups cannot be combined in order to improve force to a greater level.     

Time-of-day effects in maximal anaerobic leg exercise in tropical environment: a first approach

The aim of this study was to establish the effect of time of day on maximal anaerobic leg power in a tropical environment (French West Indies). Twenty-three physical education students (15 males and 8 females) who trained 10.5 hours a week (SD 6) volunteered to participate in the study. Their mean age, height and body mass were 22.8 (SD 3) years, 172.6 (SD 8) cm, and 64.6 (SD 7) kg, respectively. The chronotype of all subjects was moderate or intermediate. Tests were scheduled at 08 : 00, 13 : 00 and 17 : 00 hours on separate days in random order and constant conditions (room temperature: 28.1 degrees C [SD 0.6], relative room humidity: 62.6 % [SD 3.4]). On test days, the subjects were first measured at rest for body mass, heart rate and rectal temperature and they then performed vertical jump tests and a force-velocity test. The results showed a time-of-day effect on rectal temperature, which was significantly (p < 0.005) higher by the afternoon (13 : 00 and 17 : 00) than the morning (08 : 00). However, our results failed to show any daytime variation in maximal anaerobic power under the influence of tropical climate, which suggests that a hot and humid environment may have blunted the time-of-day effect by a passive warm-up effect.     

Effect of an acute hot and dry exposure in moderately warm and humid environment on muscle performance at different times of day

This study investigated whether 30 min of acute hot exposure has an additional passive warm-up effect for the improvement in muscle performance in a moderately warm and humid environment. We also sought to determine whether this effect is dependent on the diurnal variation in body temperature. Nine male subjects (age: 31.9 [+/- 5] years, height: 177 [+/- 6] cm, body mass: 69.3 [+/- 10] kg) were tested (CMJ, cycling sprints, and isokinetic contractions of the knee flexors and extensors) in a moderately warm and humid environment (24 [+/- 1] degrees C and 70 [+/- 4] % rh) with and without acute heat exposure (30 min of rest in a sauna at 76 [+/- 2] degrees C and 27 [+/- 1] % rh), both in the morning (07:00 - 09:00 h) and in the evening (17:00 - 19:00 h). Our results indicated a significant effect of both time-of-day and acute heat exposure on leg skin temperature (p < 0.01) but failed to show any effect of time-of-day or acute heat exposure on the various evaluated parameters (CMJ: speed, force, power and height; cycling power: over a half pedal revolution and a total pedal revolution; isokinetic torque: knee extensor and flexor muscles at 4.19 rad x s (-1), 3.14 rad x s (-1), 2.09 rad x s (-1), and 1.05 rad x s (-1)). In conclusion, our data suggest that 30 min of acute hot exposure does not have any passive warm-up effect in a moderately warm and humid environment. Furthermore, the diurnal variation in body temperature has no passive warm-up effect in a moderately warm and humid or in an extremely hot environment.     

Reproducibility of diurnal variation in sub-maximal swimming

Swimming training is characterised by the use of early morning and evening training sessions. The purpose of the present study was to investigate if the physiological and kinematic responses to swimming a typical training set are affected by time of day. Seven male collegiate swimmers (age 22 +/- 4 years; height 1.8 +/- 0.1 m; mass 82.1 +/- 4.1 kg) completed a standardised 600 m warm up followed by a 10 x 100 m sub-maximal freestyle set twice a day (06:30-08:00 h and 16:30-20:00 h) on three separate days. Swimming speed was controlled precisely throughout (limits of agreement multiplied/divided 1.00) using a new pacing device (Aquapacer, Challenge and Response, Inverurie, Scotland). Oral temperature (To), heart rate (HR), minute ventilation (VE), oxygen uptake (VO2), carbon dioxide expired (VCO2), respiratory exchange ratio (RER), capillary blood lactate (Bla), and glucose (BGL) were measured at rest and post exercise. Stroke rate (SR) and HR were measured during the first nine 100 m repetitions while rate of perceived exertion (RPE) was measured immediately after each 100 m. Significant diurnal variation was found at rest in To, HR, and VO2 on all three days and for VE and VCO2 on two of the days (P<0.05). During the training set no diurnal variation was evident in HR and SR responses or repetition times although RPE values were higher in morning trials compared to evening trials on two of the three days (P < 0.05). Post-exercise significant diurnal variation was found for To and blood glucose for two of the three days (P < 0.05). Therefore, although diurnal variation is evident at rest, there is no subsequent effect on physiological and kinematic responses during a sub-maximal training set following a standardised warm-up.     

Effects of different pedalling techniques on muscle fatigue and mechanical efficiency during prolonged cycling

The present study aimed to test the influence of the pedalling technique on the occurrence of muscular fatigue and on the energetic demand during prolonged constant‐load cycling exercise. Subjects performed two prolonged (45 min) cycling sessions at constant intensity (75% of maximal aerobic power). In a random order, participants cycled either with their preferred technique (PT) during one session or were helped by a visual force‐feedback to modify their pedalling pattern during the other one (FB). Index of pedalling effectiveness was significantly (P<0.05) improved during FB (41.4±5.5%); compared with PT (36.6±4.1%). Prolonged cycling induced a significant reduction of maximal power output, which was greater after PT (?15±9%) than after FB (?7±12%). During steady‐state FB, vastus lateralis muscle activity was significantly (P<0.05) reduced, whereas biceps femoris muscles activities increased compared with PT. Gross efficiency (GE) did not significantly differ between the two sessions, except during the first 15 min of exercise (FB: 19.0±1.9% vs PT: 20.2±1.9%). Although changes in muscular coordination pattern with feedback did not seem to influence GE, it could be mainly responsible for the reduction of muscle fatigue after prolonged cycling.     

Effects of the time of day on repeated all-out cycle performance and short-term recovery patterns

The effect of the time of day on repeated cycle sprint performance and short-term recovery patterns was investigated in 12 active male subjects (23+/-2 years, 76.4+/-4.2 kg, 1.80+/-0.06 m, 9.5+/-4.5 h . week (-1) of physical activity). Subjects performed ten 6-s maximal sprints inter-spaced by 30 s rest in the morning (08 : 00-10 : 00 h) and in the evening (17 : 00-19 : 00 h) on separate days. During the intermittent exercise, peak power output (P (PO), watts), total mechanical work (W, kJ), peak pedalling rate (P (PR), rev . min (-1)), and peak efficient torque (P (TCK), Nm) were recorded. The values at the 1st, the 5th, and the 10th sprints were used as mechanical indices of fatigue occurrence. Intra-aural temperature and maximal voluntary contraction of knee extensors muscles (MVC) were measured before (pre), immediately after (post) the cycle bouts and following a 5-min passive recovery period (post 5). The MVC indices were used to further confirm occurrence of neuromuscular fatigue and to assess short-term recovery patterns from all-out intermittent effort. During the MVC, electromyographic activity of the vastus lateralis muscle was recorded and analysed as its root mean square (RMS). The torque produced per unit RMS was calculated and used as index of neuromuscular efficiency (NME). A main effect for the sprint number was observed for all cycle performance parameters (p<0.05). The main effect for the time of day was not significant for any biomechanical indices of neuromuscular performance. A significant interaction effect of the time of day and the sprint repetition was demonstrated on P (TCK) ( F(2,22)=4.3, p<0.05). The decrease in P (TCK) consecutive to sprint repetition was sharper in the evening compared to the morning (sprint 10[% of sprint 1]:-9.5 % in the evening vs. - 2.2 % in the morning, p<0.05). Significant interaction effects of the time of day and the condition (i. e. pre, post, post 5) were also demonstrated for RMS ( F(2,22)=3.6, p<0.05) and NME ( F(2,22)=4.5, p<0.05) during MVC. These interactions were characterised by similar patterns of fatigue occurrence (i. e. post vs. pre condition) in the morning (+7.5 % for RMS, - 19.6 % for NME) as in the evening (+10.2 % for RMS, -19.4 % for NME) but different patterns of short-term recovery (i. e. post 5 vs. post condition; p<0.05) in the morning (-7.3 % for RMS, +13.7 % for NME) compared to the evening (+3.3 % for RMS, -1.8 % for NME). These results suggest that short-term recovery patterns of neuromuscular function are slower in the evening compared to the morning.     

Diurnal variation in maximal and submaximal strength, power and neural activation of leg extensors in men: multiple sampling across two consecutive days

This study aimed to compare day-to-day repeatability of diurnal variation in strength and power. Thirty-two men were measured at four time points (07 : 00 - 08 : 00, 12 : 00 - 13 : 00, 17 : 00 - 18 : 00, and 20 : 30 - 21 : 30 h) throughout two consecutive days (day 1 and day 2). Power during loaded squat jumps, torque and EMG during maximal (MVC) and submaximal (MVC40) voluntary isometric knee extension contractions were measured. The EMG/torque ratio during MVC and MVC40 was calculated to evaluate neuromuscular efficiency. A significant time-of-day effect with repeatable diurnal patterns was found in power. In MVC, a significant time-of-day effect was present on day 2, whereas day 1 showed a typical but nonsignificant diurnal pattern. EMG and antagonist co-activation during MVC remained statistically unaltered, whereas neuromuscular efficiency improved from day 1 to day 2. A similar trend was observed in MVC40 neuromuscular efficiency with significant time-of-day and day-to-day effects. Unaltered agonist and antagonist activity during MVC suggests that modification at the muscular level was the primary source for the diurnal variation in peak torque. A learning effect seemed to affect data in MVC40. In conclusion, the second consecutive test day showed typical diurnal variation in both maximum strength and power with no day-to-day effect of cumulative fatigue.     

Different effects of heat exposure upon exercise performance in the morning and afternoon

Independent of environmental conditions, rectal temperature follows a circadian rhythm with an acrophase in the late afternoon. In neutral environment, this diurnal increase in temperature is believed to have a passive warm-up effect improving muscle contractility, and in turn, muscle force, power and performance. However, a hot environment blunts the diurnal variation in muscle function by only improving muscle contractility, and in turn, muscle force, power and performance in the morning, when body temperature is at its lowest. Despite this diurnal variation in muscle function, long-duration exercise is only slightly affected by the time-of-day in neutral environment. However, higher afternoon body temperatures can reduce the heat storage capacity and result in a reduction in exercise capacity in hot environments. In addition, in parallel to the circadian variations in muscle contractility and central temperature, exercise capacity in hot environment may also be affected by the diurnal variations in melatonin concentration and in the onset of peripheral vasodilatation and sweating.     

雷达作业人员白班作业后工作绩效和主观工作负荷的变化

目的 观察雷达作业人员白班作业后工作绩效和主观工作负荷的变化.方法 根据某雷达部队正常工作班次,对21名男性雷达作业人员白班(8:00-12:00为上午班,12:00-18:00为下午班)作业前后分别进行跟踪计算机模拟雷达信号、识别目标绩效、临界闪光融合频率(critical flicker fusion frequency,CFF)和数字划消成绩测试,同时对工作负荷进行主观测评.结果 上、下午班后的CFF值(分别为30.34±1.49、31.11±1.53)较班前(分别为31.61±1.84、32.41±2.13)显著降低(t=5.49、4.64,P＜0.01),班后的主观工作负荷(分别为4.94±0.85、5.06±0.77)较班前(分别为1.88±0.72、1.63±0.50)明显升高(t=9.91、14.26,P＜0.01).此外,与班前相比,上午班后的雷达信号标识任务时间明显延长(t=2.51,P＜0.05),下午班后的数字错划数与漏划数明显增多(t=2.85、2.24,P＜0.05).结论 雷达作业人员在白班连续作业后出现明显疲劳,表现为工作绩效下降、主观工作负荷增加. Abstract： Objective To compare the change of performance and subjective workload of radar operators after day shift. Methods Twenty-one radar operators in a troop were selected as subjects. Their performances of pursuing computer simulated radar signal and recognizing target and fatigue degree, which scaled by the critical flicker fusion frequency (CFF) and the score of crossing out, were tested before and after the duty of day shift(8:00-12:00 and 12:00-18:00 was defined as morning and afternoon shift respectively). The subjective evaluation of workload was done at same time.Results CFF value that measured after morning and afternoon shift was respectively 30.34±1.49 Hz and 31.11±1.53 Hz, which was significantly lower than that before morning (31.61±1.84)and afternoon shift (32.41±2.13) (t=5.49, 4.64, P＜0.01). The subjective workload after shifts (4.94±0.85, 5.06±0.77) was respectively increased (t=9.91, 14.26, P＜0.01) comparing with that before shifts. In comparison of the state before shift, the time of recognizing radar signal after morning shift was significantly longer (t=2.51, P＜0.05) and the errors of crossing out after afternoon shift was significantly increased (t=2.85, 2.24, P＜0.05). Conclusions Continued day shift would cause radar operators' significant fatigue that appeared as decreased performance and increased subjective workload.     

Evidence of neuromuscular fatigue after prolonged cycling exercise

PURPOSE: The purpose of this study was to analyze the effects of prolonged cycling exercise on metabolic, neuromuscular, and biomechanical parameters. METHODS: Eight well-trained male cyclists or triathletes performed a 2-h cycling exercise at a power output corresponding to 65% of their maximal aerobic power. Maximal concentric (CON; 60, 120, 240 degrees x s(-1)), isometric (ISO; 0 degrees s(-1)), and eccentric (ECC; -120, -60 degrees x s(-1)) contractions, electromyographic (EMG) activity of vastus lateralis (VL) and vastus medialis (VM) muscles were recorded before and after the exercise. Neural (M-wave) and contractile (isometric muscular twitch) parameters of quadriceps muscle were also analyzed using electrical stimulation techniques. RESULTS: Oxygen uptake (VO2), minute ventilation (VE), and heart rate (HR) significantly increased (P < 0.01) during the 2-h by, respectively, 9.6%, 17.7%, and 12.7%, whereas pedaling rate significantly decreased (P < 0.01) by 21% (from 87 to 69 rpm). Reductions in muscular peak torque were quite similar during CON, ISO, and ECC contractions, ranging from 11 to 15%. M-wave duration significantly increased (P < 0.05) postexercise in both VL and VM, whereas maximal amplitude and total area decreased (VM: P < 0.05, VL: NS). Significant decreases in maximal twitch tension (P < 0.01), total area of mechanical response (P < 0.01), and maximal rate of twitch tension development (P < 0.05) were found postexercise. CONCLUSIONS: A reduction in leg muscular capacity after prolonged cycling exercise resulted from both reduced neural input to the muscles and a failure of peripheral contractile mechanisms. Several hypothesis are proposed to explain a decrease in pedaling rate during the 2-h cycling with a constancy of power output and an increase in energy cost.     

Influence of time of day on all-out swimming

The effect of time of day on all-out swim performances was examined. Fourteen subjects performed maximal front crawl swim tests on separate days over 100 m. and 400 m. at 5 different times of day between 06.30 h. and 22.00 h. Performance showed a significant linear trend with time of day in close though not exact association with the circadian rhythm in oral temperature: a goodness of fit test confirmed that the values predicted from linear trend analysis coincided with the measured values (p less than 0.05). The steady improvement throughout the day was 3.5% for 100 m. and 2.5% for 400 m. swims. Trunk flexibility displayed a time of day variation with a trough in the morning and a peak in the afternoon. No significant rhythm was observed in ankle and shoulder flexibility, grip strength or peak expiratory flow rate (p greater than 0.05). It was concluded that maximal swimming trials are best scheduled for the evening and worst in the early morning. Specific fitness factors cannot clearly account for the higher exercise capability in the evening which is strongly related to the circadian curve in body temperature.     

Effect of time of day on adaptive response to a 4-week aerobic exercise program.

The circadian effects of an aerobic training program were studied in 3 groups of men who exercised at different times of day. Twelve healthy sedentary men were assigned to morning (9:00-9:30), afternoon (15:00-15:30) or evening (20:00-20:30) exercise groups. Each group performed a 30-minute 60% VO2max cycle ergometer exercise 4 days per week over a 4-week period. Maximal oxygen uptake (VO2max) was estimated and adaptive responses of heart rate and blood lactate levels to the training program were measured. After 4 weeks, the afternoon group showed a significant increase in estimated VO2max. A significant decrease in heart rate and blood lactate responses occurred in the afternoon and morning groups and the afternoon and evening groups, respectively. These results suggest that aerobic training is most effective in the afternoon.     

Diurnal variation in long- and short-duration exercise performance and mood states in boys

The aim of the present study was to investigate the effect of time-of-day on long- and short-duration exercise performance and mood states. Twelve prepubertal boys (age 10.7 ± 0.4 years; height 1.47 ± 0.6 m; body-mass 44.8 ± 3.1 kg) performed three test sessions at 08:00, 14:00 and 18:00 h. During each session, they performed the squat jump (SJ), the countermovement jump (CMJ) and the Yo–Yo test. Oral temperature was recorded at the beginning of each test session. Moreover, boys completed the profile of mood states questionnaire before performing the physical tests. The results showed that SJ (p < 0.05), CMJ (p < 0.01) and oral temperature (p < 0.001) were higher at 14:00 and 18:00 h compared to 08:00 h. Maximal aerobic velocity during the Yo–Yo test was higher only at 18:00 h than 08:00 h (p < 0.05). However, mood states were not significantly different between 08:00, 14:00 and 18:00 h. Likewise, we did not observe significant correlations between mood states and physical performances. In conclusion, in boys, both long- and short-duration exercises, performances were better in the afternoon than the morning.     

急性低压缺氧对飞行人员血浆乳酸及乳酸脱氢酶含量的影响

目的：探讨急性低压缺氧对飞行人员血浆乳酸（ＬＡ）及乳酸脱氢酶（ＬＤＨ）含量的影响。方法：用比色法测定了１６名健康男性歼击机飞行人员清晨（６：００ａ．ｍ．）、急性中度低压缺氧２０ｍｉｎ后即刻（１０：００ａ．ｍ．）及下降至地面６ｈ后（４：００ｐ．ｍ．）的血浆ＬＡ及ＬＤＨ含量,并以１６名健康男性地面人员相应时间的测定作对照。结果：实验组急性中度低压缺氧２０ｍｉｎ后即刻,血浆ＬＡ水明显高于实验前及实验后６ｈ,也高于同一时间对照组（Ｐ＜０．０１）,实验后６ｈ时血浆ＬＡ含量下降,与实验前及同一时间对照组相比较无显著性差异（Ｐ＞０．０５）。实验组急性中度低压缺氧２０ｍｉｎ后即刻,血浆乳酸脱氢酶含量与实验前及实验后６ｈ以及同一时间对照组相比均无显著性差异（Ｐ＞０．０５）。结论：急性中度低压缺氧能使飞行人员血浆乳酸水平升高,出舱     

Diurnal patterns of objectively measured sedentary time and interruptions to sedentary time are associated with glycaemic indices in type 2 diabetes

ObjectivesTo investigate diurnal patterns of sedentary time and interruptions to sedentary time and their associations with achievement of pre-meal glucose, post-meal glucose, bedtime glucose and the dawn phenomenon targets and with duration of hypoglycaemia, euglycaemia, hyperglycaemia and above target range.DesignIntensive longitudinal study.MethodsIn 37 adults with type 2 diabetes, the FreeStyle Libre and activPAL3 were used to monitor glucose and sedentary time and interruptions to sedentary time in the morning (07:00–12:00), afternoon (12:00–17:00) and evening (17:00–23:00) for 14 days. Diurnal patterns of sedentary behaviour and associations with glycaemic indices were assessed using repeated measures ANOVA and linear regressions.ResultsSedentary time was significantly higher in the evening (43.47 ± 7.37 min/h) than the morning (33.34 ± 8.44 min/h) and afternoon (37.26 ± 8.28 min/h). Interruptions to sedentary time were significantly lower in the evening (2.64 ± 0.74 n/h) than the morning (3.69 ± 1.08 n/h) and afternoon (3.06 ± 0.87 n/h). Sedentary time in the morning and afternoon was associated with lower achievement of the dawn phenomenon target. Sedentary time in the evening was associated with lower achievement of post-lunch glucose target. Interruptions to sedentary time in the morning and afternoon were associated with higher achievement of pre-dinner glucose target. Interruptions to sedentary time in the evening showed beneficial associations with achievement of post-dinner glucose and bedtime glucose targets and euglycaemia.ConclusionsProlonged sedentary behaviour is high in the evening. Interruptions to sedentary time, particularly in the evening, have beneficial associations with glycaemic indices. Interventions targeting interruptions to sedentary time in the evening may be more clinically relevant.