Influence of anthropometric characteristics on changes in maximal exercise ventilation and breathing pattern during growth in boys

Summary The aim of this study was to investigate the effect of growth on ventilation and breathing pattern during maximal exercise oxygen consumption (VO_2max and their relationships with anthropometric characteristics. Seventy six untrained schoolboys, aged 10.5–15.5 years, participated in this study. Anthropometric measurements made included body mass, height, armspan, lean body mass, and body surface area. During an incremental exercise test, maximal ventilation (V_Emax), tidal volume (V _Tmax), breathing frequency (f _max), inspiratory and expiratory times (t _Imax and t _Emax), total duration of respiratory cycle (t _TOTmax), mean inspiratory flow (V _T/t _Imax), and inspiration fraction (t _I/t _TOTmax) were measured at VO_2max. A power function was calculated between anthropometric characteristics and ventilatory variables to determine the allometric constants. The results showed firstly, that V_Emax, V _Tmax, t _Imax, t _Emax, t _TOTmax, and V _T/t _Imax increased with age and anthropometric characteristics (P<0.001), f _max decreased (P<0.001), and t _I/t _TOTmax remained constant during growth; secondly that lean body mass explained the greatest percentage of variance of V_Emax (62.1%), V _Tmax (76.8%), and V _T/t _Imax (70.6%), while anthropometric characteristics explained a slight percentage of variance of f _max and timing; and thirdly that V_Emax, V _Tmax, and V _T/t _Imax normalized by lean body mass did not change significantly with age. We concluded that at VO_2max there were marked changes in ventilation and breathing pattern with growth. The changes in V_Emax, V _Tmax, and V _T/t _Imax were strongly related to the changes in lean body mass.     

Peak power output predicts maximal oxygen uptake and performance time in trained cyclists

Summary The purposes of this study were firstly to determine the relationship between the peak power output (W _peak) and maximal oxygen uptake (VO_2max) attained during a laboratory cycling test to exhaustion, and secondly to assess the relationship betweenW _peak and times in a 20-km cycling trial. One hundred trained cyclists (54 men, 46 women) participated in the first part of this investigation. Each cyclist performed a minimum of one maximal test during whichW _max andVO_2max were determined. For the second part of the study 19 cyclists completed a maximal test for the determination ofW _peak, and also a 20-km cycling time trial. Highly significant relationships were obtained betweenW _peak andVO_2max (r=0.97,P<0.0001) and betweenW _peak and 20-km cycle time (r= –0.91,P<0.001). Thus,W _peak explained 94% of the variance in measuredVO_2max and 82% of the variability in cycle time over 20 km. We concluded that for trained cyclists, theVO_2max can be accurately predicted fromW _peak, and thatW _peak is a valid predictor of 20-km cycle time.     

Changes in maximal exercise ventilation and breathing pattern in boys during growth: a mixed cross-sectional longitudinal study

The aim of this mixed cross-sectional longitudinal study covering a total age range of 11–17 years, i.e. the entire pubertal growth period, was (1) to specify the changes in maximal breathing pattern during incremental exercise; (2) to determine what parts of the changes are due to anthropometric characteristics, physical fitness and inspiratory or expiratory muscle strength; and (3) to determine if the role of these variables is identical before, during and after pubertal growth spurt. This study was conducted in 44 untrained schoolboys separated into three groups, with an initial age of 11.2 ± 0.2 years for group A, 12.9 ± 0.25 years for group B, and 14.9 ± 0.26 years for group C. These children were subsequently followed for 3 years, during the same time period each year. The maximal inspiratory and expiratory pressures (P_{I max} and P_{E max}) were used as an index of the respiratory muscle strength. During an incremental exercise test, maximal ventilation (V˙_{E max}), tidal volume (V_{T max}), breathing frequency (f_max), inspiratory and expiratory times (t_{I max} and t_{E max}) and mean inspiratory flow (V_T/t_{I max}) were measured at maximal oxygen uptake (V˙_O2max). Our study showed that there was a marked increase with age in V˙_{E max}, V_{T max}, and V_T/t_{I max} , and no significant changes in f_max, t_{I max} and t_{E max}. P_{I max} and P_{E max} showed a general trend towards an increase between 11 and 17 years. The study of the linear correlations between maximal breathing pattern and the anthropometric characteristics, physical fitness and inspiratory or expiratory muscle strength showed that, in the three groups of children, (1) lean body mass was the major determinant of V˙_{E max}, V_{T max} and V_T/t_{I max} and the relationships were significantly different before, during and after the pubertal growth spurt; (2) physical fitness was the main determinant of t_{I max}, t_{E max} and f_max before and after the pubertal growth spurt; and (3) maximal respiratory strength did not play a significant role. In conclusion, this mixed cross-sectional longitudinal study showed, at maximal exercise, a significant increase in V˙_{E max} during growth due only to a significant increase in V_{T max} and V_T/t_{I max}, and that the relationships of anthropometric characteristics and physical fitness with maximal breathing pattern change during growth.     

Maximal oxygen uptake during field running does not exceed that measured during treadmill exercise

Modern ergometric equipment enables the simulation of laboratory maximal oxygen uptake (V˙O_2max) testing in the field. Therefore, it was investigated whether the improved event specificity on the track might lead to higher V˙O_2max measurements in running. Identical protocols were used on the treadmill and on the track (speed was indicated by a computer-driven flashing light system). Ambulatory measurements of gas exchange were carried out throughout both tests, which were executed in randomized order. There were no significant differences (P=0.71) in V˙O_2max between treadmill [4.65 (0.51) ml·min^–1] and field tests [4.63 (0.55) ml·min^–1]. However, the test duration differed significantly (P<0.001) by approximately 5%: treadmill 691 (39) s; field test 727 (42) s. With the exception of maximum heart rate (HR_max; significantly higher in the field with P=0.02) all criteria for the degree of effort were similar between the two tests. However, the difference in HR_max at less than 2 beats·min^–1, was practically negligible. Submaximal measurements of oxygen uptake and minute ventilation were significantly higher on the treadmill (P<0.001 for both parameters). In summary, field tests with incremental running protocols do not result in higher V˙O_2max measurements compared to laboratory treadmill exercise. A better running economy on the track results in higher maximal velocities and longer exercise durations being sustained. The determination of V˙O_2max is not a reasonable application for ambulatory gas exchange measurements because laboratory values are not surpassed. Electronic Publication     

Caffeine increases maximal anaerobic power and blood lactate concentration

Summary The aim of this study was to specify the effects of caffeine on maximal anaerobic power (W _max). A group of 14 subjects ingested caffeine (250 mg) or placebo in random double-blind order. TheW _max was determined using a force-velocity exercise test. In addition, we measured blood lactate concentration for each load at the end of pedalling and after 5 min of recovery. We observed that caffeine increasedW _max [964 (SEM 65.77) W with caffeine vs 903.7 (SEM 52.62) W with placebo;P<0.02] and blood lactate concentration both at the end of pedalling [8.36 (SEM 0.95) mmol · l^–1 with caffeine vs 7.17 (SEM 0.53) mmol · l^–1 with placebo;P<0.011 and after 5 min of recovery [10.23 (SEM 0.97) mmol · l^–1 with caffeine vs 8.35 (SEM 0.66) mmol · l^–1 with placebo;P<0.04]. The quotient lactate concentration/power (mmol · l^–1 · W^–1) also increased with caffeine at the end of pedalling [7.6 · 10^–3 (SEM 3.82 · 10^–5) vs 6.85 · 10^–3 (SEM 3.01 · 10^–5);P<0.01] and after 5 min of recovery [9.82·10^–3 (SEM 4.28 · 10^–5) vs 8.84 · 10^–3 (SEM 3.58 · 10^–5);P<0.02]. We concluded that caffeine increased bothW _max and blood lactate concentration.     

Effect of training in humans on off- and on-transient oxygen uptake kinetics after severe exhausting intensity runs

The purpose of this study was to examine the effect of 4 weeks of intense interval-training on the pulmonary off-transient oxygen uptake (VO₂) after running until exhaustion at the same absolute speed. Seven physical education students ran as follows in three maximal tests on a synthetic track (400 m) whilst breathing through a portable, telemetric metabolic analyser: firstly, in an incremental test which determined maximal oxygen uptake (VO_2max), the minimal speed associated with VO_2max (vVO₂max) and the speed at the lactate threshold (v _LT). Secondly, in two continuous severe intensity runs at 90% (R90) and 95% (R95) of vVO_2max. After training, the times to exhaustion (t _lim) at these two speeds (i.e. the time limits t _lim90 and t _lim95, respectively), were significantly increased at both speeds (+37% and +66% for t _lim90 and t _lim95, P=0.04 and 0.01, respectively) and v _LT and vVO₂max were increased by 8% and 5%, respectively (P<0.02). The time constants of the cardio-dynamic added to the metabolic phase (phases I+II) and of the slow phase (phase III) of oxygen kinetics in the on-transient phase decreased significantly after training (P=0.05). However, the decrease in the time constants of oxygen kinetics in the on-transient phases II and III were not correlated with the improvement in performance (i.e. increase in t _lim). After training the VO₂ off-transient phase was significantly faster [off-time constant (τ_off) decreased significantly both after R90 and R95, P=0.03]. This decrease in τ_off was correlated with the increase in t _lim90 (r=0.795, P=0.03). The physiological factors best correlated with the increased performance after training were v _LT for t _lim90 and vVO₂max for t _lim95. Electronic Publication     

Factors limiting maximal performance in humans

Theoretical best performance times (t_theor) in track running are calculated as follows. Maximal metabolic power (Ė_max) is a known function of maximal oxygen uptake (O_2max), of maximal anaerobic capacity (AnS) and of effort duration to exhaustion (t_e): Ė_max=f (t_e). Metabolic power requirement (Ė_r) to cover the distance (d) in the performance time t_p is the product of the energy cost of locomotion per unit distance (C) and the speed: Ė_r=C×d/t_p. The time values for which Ė_max (t_e)=Ė_r (t_p), assumed to yield t_theor, can be obtained for any given subject and distance provided that O_2max, AnS and C are known, and compared with actual best performances (t_act). For 15 mint_e100 s, the overall ratio t_act/t_theor was rather close to 1.0. To estimate the relative role of the different factors limiting O_2max, several resistances to O₂ transport are identified, inversely proportional to: alveolar ventilation (R_V*), O₂ transport by the circulation (R_Q), O₂ diffusion from capillary blood to mitochondria (R_t), mitochondrial capacity (R_m). Observed changes of O_2max are accompanied by measured changes of several resistances. The ratio of each resistance to the overall resistance can therefore be calculated by means of the O₂ conductance equation. In exercise with large muscle groups (two legs), R_Q is the major (75%) limiting factor downstream of the lung, its role being reduced to 50% during exercise with small muscle groups (one leg). R_t and R_m account for the remaining fractions. In normoxia R_V* is negligible; at high altitude it increases progressively, together with R_t and R_m, at the expense of R_Q.     

Comparison between maximal power in the power-endurance relationship and maximal instantaneous power

The purpose of this study was to analyze the relevance of introducing the maximal power ( P _m) into a critical-power model. The aims were to compare the P _m with the instantaneous maximal power ( P _max) and to determine how the P _m affected other model parameters: the critical power ( P _c) and a constant amount of work performed over P _c ( W ). Twelve subjects [22.9 (1.6) years, 179 (7) cm, 74.1 (8.9) kg, 49.4 (3.6) ml/min/kg] completed one 15 W/min ramp test to assess their ventilatory threshold (VT), five or six constant-power to exhaustion tests with one to measure the maximal accumulated oxygen deficit (MAOD), and six 5-s all-out friction-loaded tests to measure P _max at 75 rpm, which was the pedaling frequency during tests. The power and time to exhaustion values were fitted to a 2-parameter hyperbolic model (NLin-2), a 3-parameter hyperbolic model (NLin-3) and a 3-parameter exponential model (EXP). The P _m values from NLin-3 [760 (702) W] and EXP [431 (106) W] were not significantly correlated with the P _max at 75 rpm [876 (82) W]. The P _c value estimated from NLin-3 [186 (47) W] was not significantly correlated with the power at VT [225 (32) W], contrary to other models ( P <0.001). The W from NLin-2 [25.7 (5.7) kJ] was greater than the MAOD [14.3 (2.7) kJ, P <0.001] with a significant correlation between them ( R =0.76, P <0.01). For NLin-3, computation of W _{P >P c}, the amount of work done over P _C, yielded results similar to the W value from NLin-2: 27.8 (7.4) kJ, which correlated significantly with the MAOD ( R =0.72, P <0.01). In conclusion, the P _m was not related to the maximal instantaneous power and did not improve the correlations between other model parameters and physiological variables.     

Force-velocity relationship and maximal power on a cycle ergometer

Summary The force-velocity relationship on a Monark ergometer and the vertical jump height have been studied in 152 subjects practicing different athletic activities (sprint and endurance running, cycling on track and/or road, soccer, rugby, tennis and hockey) at an average or an elite level. There was an approximatly linear relationship between braking force and peak velocity for velocities between 100 and 200 rev · min⁻¹. The highest indices of force P₀, velocity V₀ and maximal anaerobic power (W_max) were observed in the power athletes. There was a significant relationship between vertical jump height and W_max related to body mass.     

Neuromuscular factors determining 5 km running performance and running economy in well-trained athletes

This study investigated the effects of the neuromuscular and force–velocity characteristics in distance running performance and running economy. Eighteen well-trained male distance runners performed five different tests: 20 m maximal sprint, running economy at the velocity of 4.28 m s⁻¹, 5 km time trial, maximal anaerobic running test (MART), and a treadmill test to determine VO_2max. The AEMG ratio was calculated by the sum average EMG (AEMG) of the five lower extremity muscles during the 5 km divided by the sum AEMG of the same muscles during the maximal 20 m sprinting. The runners’ capacity to produce power above VO_2max (MART VO_2gain) was calculated by subtracting VO_2max from the oxygen demand of the maximal velocity in the MART (V _MART). Velocity of 5 km (V _5K) correlated with V _MART (r=0.77, p<0.001) and VO_2max (r=0.49, p<0.05). Multiple linear regression analysis showed that MART VO_2gain and VO_2max explained 73% of the variation in V _5K. A significant relationship also existed between running economy and MART VO_2gain (r=0.73, p<0.01). A significant correlation existed between V _5K and AEMG ratio during the ground contact phase at the 3 km (r=0.60, p<0.05) suggesting that neural input may affect distance running performance. The results of the present study support the idea that distance running performance and running economy are related to neuromuscular capacity to produce force and that the V _MART can be used as a determinant of distance-running performance.     

Anaerobic threshold and maximal steady-state blood lactate in prepubertal boys

Summary To elucidate further the special nature of anaerobic threshold in children, 11 boys, mean age 12.1 years (range 11.4–12.5 years), were investigated during treadmill running. Oxygen uptake, including maximal oxygen uptake (VO_2max), ventilation and the ventilatory anaerobic threshold were determined during incremental exercise, with determination of maximal blood lactate following exercise. Within 2 weeks following this test four runs of 16-min duration were performed at a constant speed, starting with a speed corresponding to about 75% ofVO_2max and increasing it during the next run by 0.5 or 1.0 km·h^–1 according to the blood lactate concentrations in the previous run, in order to determine maximal steady-state blood lactate concentration. Blood lactate was determined at the end of every 4-min period. Anaerobic threshold was calculated from the increase in concentration of blood lactate obtained at the end of the runs at constant speed. The mean maximal steady-state blood lactate concentration was 5.0 mmol · 1^–1 corresponding to 88% of the aerobic power, whereas the mean value of the conventional anaerobic threshold was only 2.6 mmol · 1^–1, which corresponded to 78% of theVO_2max. The correlations between the parameters of anaerobic threshold, ventilatory anaerobic threshold and maximal steady-state blood lactate were only poor. Our results demonstrated that, in the children tested, the point at which a steeper increase in lactate concentrations during progressive work occurred did not correspond to the true anaerobic threshold, i.e. the exercise intensity above which a continuous increase in lactate concentration occurs at a constant exercise intensity.     

The influence of body position on maximal performance in cycling

Summary Six healthy male subjects performed a 3-min supramaximal test in four different cycling positions: two with different trunk angles and two with different saddle-tube angles. Maximal power output and maximal oxygen uptake (VO_2max) were measured. Maximal power output was significantly higher in a standard sitting (SS, 381 W, SD 49) upright position compared to all other positions: standard racing (SR, 364 W, SD 49), recumbent backwards (RB, 355 W, SD 44) and recumbent forwards (RF, 341 W, SD 54). Although VO_2max was also highest in SS (4.31 l · min^–1, SD 0.5) upright position, the differences in VO_2max were not significant (SR, 4.21 · min^–1, SD 0.53; RB, 4.17 l · min^–1, SD 0.58; RF, 4.11 l · min^–1, SD 0.66). It is concluded that (supra)maximal tests on a cycle ergometer should be performed in a sitting upright position and not in a racing position. In some cases when cycling on the road, higher speeds can be attained when sitting upright. This is especially true when cycling uphill when high power must be generated to overcome gravity but the road speed, and hence the power required to overcome air resistance, is relatively low.     

Effects of prolonged cycle ergometer exercise on maximal muscle power and oxygen uptake in humans

Summary The mechanical power (W_tot, W·kg^–1) developed during ten revolutions of all-out periods of cycle ergometer exercise (4–9 s) was measured every 5–6 min in six subjects from rest or from a baseline of constant aerobic exercise [50%–80% of maximal oxygen uptake (VO_2max)] of 20–40 min duration. The oxygen uptake [VO₂ (W·kg^–1, 1 ml O₂ = 20.9 J)] and venous blood lactate concentration ([la]_b, mM) were also measured every 15 s and 2 min, respectively. During the first all-out period, W_tot decreased linearly with the intensity of the priming exercise (W_tot = 11.9–0.25·VO₂). After the first all-out period (i greater than 5–6 min), and if the exercise intensity was less than 60% VO_2max, W_tot, VO₂ and [la]_b remained constant until the end of the exercise. For exercise intensities greater than 60% VO_2max, VO₂ and [la]_b showed continuous upward drifts and W_tot continued decreasing. Under these conditions, the rate of decrease of W_tot was linearly related to the rate of increase of V [(d W_tot/dt) (W·kg^–1·s^–1) = 5.0·10^–5 –0.20·(d VO₂/dt) (W·kg^–1·s^–1)] and this was linearly related to the rate of increase of [la]_b [(d VO₂/dt) (W·kg^–1·s^–1) = 2.310^–4 + 5.910^–5·(d [la]_b/dt) (mM·s^–1)]. These findings would suggest that the decrease of W_tot during the first all-out period was due to the decay of phosphocreatine concentration in the exercising muscles occurring at the onset of exercise and the slow drifts of VO₂ (upwards) and of W_tot (downwards) during intense exercise at constant W_tot could be attributed to the continuous accumulation of lactate in the blood (and in the working muscles).     

Neuromuscular characteristics and fatigue in endurance and sprint athletes during a new anaerobic power test

The purpose of this study was to investigate neuromuscular and energy performance characteristics of anaerobic power and capacity and the development of fatigue. Ten endurance and ten sprint athletes performed a new maximal anaerobic running power test (MARP), which consisted ofn x 20-s runs on a treadmill with 100-s recovery between the runs. Blood lactate concentration [la^–]_b was measured after each run to determine submaximal and maximal indices of anaerobic power (P _3mmol·1 ^–1,P_5mmol·1 ^–1,P_10mmol·1 ^–1andP _max) which was expressed as the oxygen demand of the runs according to the American College of Sports Medicine equation: the oxygen uptake (ml·kg^–1·min^–1)=0.2·velocity (m·min^–1) +0.9·slope of treadmill (frac)·velocity (m·min^–1)+3.5. The height of rise of the centre of gravity of the counter movement jumps before (CMJ_rest) and during (CMJ) the MARP test, as well as the time of force production (t _F) and electromyographic (EMG) activity of the leg muscles of CMJ performed after each run were used to describe the neuromuscular performance characteristics. The maximal oxygen uptake ( _max), anaerobic and aerobic thresholds were determined in the _max test, which consisted ofn x 3-min runs on the treadmill. In the MARP-testP _max did not differ significantly between the endurance [116 (SD 6) ml·kg^–1·min^–1] and sprint [120 (SD 4) ml·kg^–1·min^–1] groups, even though CMJ_rest and peak [la^–]_b were significantly higher and _max was significantly lower in the sprint group than in the endurance group and CMJ_rest height correlated withP _max (r=0.50,P<0.05). The endurance athletes had significantly higher mean values ofP _3mmol·1 ^–1andP _5mmol·1 ^–1[89 (SD 7) vs 76 (SD 8) ml·kg^–1·min^–,P<0.001 and 101 (SD 5) vs 90 (SD 8) ml·kg^–1·min^–1,P<0.01. Significant positive correlations were observed between theP _3mmol·l ^–1and _max, anaerobic and aerobic thresholds. In the sprint group CMJ and the averaged integrated iEMG decreased andt _F increased significantly during the MARP test, while no significant changes occurred in the endurance group. The present findings would suggest thatP _max reflected in the main the lactacid power and capacity and to a smaller extent alactacid power and capacity. The duration of the MARP test and the large number of CMJ may have induced considerable energy and neuromuscular fatigue in the sprint athletes preventing them from producing their highest alactacidP _max at the end of the MARP test. Due to lower submaximal [la^–]_b (anaerobic sprinting economy) the endurance athletes were able to reach almost the sameP _max as the sprint athletes.     

The influence of maximal aerobic power on recovery of skeletal muscle following anaerobic exercise

Phosphorus magnetic resonance spectroscopy (³¹P-MRS) was used to investigate the influence of maximal aerobic power (˙VO _2max) on the recovery of human calf muscle from high-intensity exercise. The (˙VOO_2max) of 21 males was measured during treadmill exercise and subjects were assigned to either a low-aerobic-power (LAP) group (n?=?10) or a high-aerobic-power (HAP) group (n?=?11). Mean (SE) ˙VO _2max of the groups were 46.6 (1.1) and 64.4 (1.4) ml?·?kg^?1?·?min^?1, respectively. A calf ergometry work capacity test was used to assign the same relative exercise intensity to each subject for the MRS protocol. At least 48 h later, subjects performed the rest (4 min), exercise (2 min) and recovery (10 min) protocol in a 1.5 T MRS scanner. The relative concentration of phosphocreatine (PCr) was measured throughout the protocol and intracellular pH (pH_i) was determined from the chemical shift between inorganic phospate (P_i) and PCr. End-exercise PCr levels were 27 (3.4) and 25 (3.5)% of resting levels for LAP and HAP respectively. Mean resting pH_i was 7.07 for both groups, and following exercise it fell to 6.45 (0.04) for HAP and 6.38 (0.04) for LAP. Analysis of data using non-linear regression models showed no differences in the rate of either PCr or pH_i recovery. The results suggest that ˙VO_2max is a poor predictor of metabolic recovery rate from high-intensity exercise. Differences in recovery rate observed between individuals with similar ˙VO_2max imply that other factors influence recovery.     

Step ergometry: is it task-specific training?

Summary Maximal exercise responses were measured before and after 10 weeks of training in two groups of men, one trained on a treadmill (n =12) and the other on a step ergometer (n=9); the groups were pre- and post-tested on both machines to examine the specificity of the training modes. Training for both groups consisted of 3 days week^–1, 30 min day^–1, progressing to 50 min day^–1, at an intensity of 75%–80% heart rate maximum reserve. Pre-training maximal oxygen uptake (VO_{2 max}) was significantly higher on the treadmill for both groups (X=8.5%). VO_2max increased 6.9% on the treadmill (P<0.05) and 6.9% (P>0.05) on the step ergometer after treadmill training. The small increases may be attributed to the specificity of the testing protocols used to elicit VO_2max. Significant (P<0.01) increases in VO_2max were found for both modalities after step-ergometry training (treadmill= 11.8%; step ergometer=23.2%). These increases resulted in equal post-test VO_2max values (4.05 l min^–1; 51 ml kg^–1 min-) on the step ergometer and treadmill. The significant increases in VO_2max found for both modalities after step-ergometry training shows that (1) step ergometry is an effective training modality, and (2) its effects can be measured on the treadmill and therefore it is not task-specific training.     

Influence of age on blood pressure recovery after maximal effort ergometer exercise in non-athletic adult males

This study investigated whether age influences blood pressure recovery after maximal exercise in adult males. Forty healthy, non-athletic adult males (20 young, aged 22 ± 3.46 years and 20 older, aged 48 ± 6.91 years) participated in the study. Subjects performed a maximal-effort ergometer exercise test. Peak oxygen uptake (VO_2max) was measured during the exercise protocol; heart rate (HR) and blood pressure (BP) were measured before exercise, during exercise (at 2-min intervals), and at the first minute of post-exercise recovery and subsequently at 2-min intervals until the recovery of BP. Results indicated that young adults had lower systolic blood pressure (SBP) recovery ratio (P < 0.05), lower SBP recovery time (P < 0.001), higher SBP% decline in 1, and 3 min (P < 0.001), and higher DBP% decline in 1, and 3 min (P < 0.05, <0.001) than the older adults, thus indicating faster BP recovery in young than older adults. A bivariate correlation test, revealed significant associations (P < 0.001, <0.01) between age and BP recovery parameters: percentage SBP decline in 1 and 3 min (27 and 39%), percentage DBP decline in 1 and 3 min (14 and 26%), third minute SBP ratio (22%), and SBP recovery time (72%). After controlling for factors affecting BP recovery such as resting SBP, percentage HR decline, VO_2max and delta SBP, the observed correlations reduced in SBP recovery time (29%; P < 0.002) but disappeared (P > 0.01) in the other BP recovery parameters. These data indicate the need to take into account, factors affecting BP recovery when interpreting the effect of age on BP responses after exercise in future investigations.     

Prediction of <Emphasis Type="Italic">V</Emphasis>O<Subscript>2max</Subscript> with daily step counts for Japanese adult women

The purpose of the study was to develop a new non-exercise VO_2max prediction model using a physical activity (PA) variable determined by pedometer-determined step counts (SC, steps day⁻¹) in Japanese women aged 20–69 years old. Eighty-seven and 102 subjects were used to develop the prediction model, and to validate the new model, respectively. VO_2max was measured using a maximal incremental test on a bicycle ergometer. SC was significantly related to VO_2max (partial correlation coefficient r = 0.40, P < 0.001) after adjusting for BMI (kg m⁻²) and age (years). When the new prediction equation developed by multiple regression to estimate VO_2max from age, BMI, and SC (R = 0.71, SEE = 5.3 ml kg⁻¹ min⁻¹, P < 0.001) was applied to the Validation group, predicted VO_2max correlated well with measured VO_2max (r = 0.81, P < 0.001), suggesting that SC is a useful PA variable for non-exercise prediction of VO_2max in Japanese women.     

Intermittent short-term graded running performance in middle-distance runners in hypobaric hypoxia

This study investigated whether in trained middle-distance runners, intermittent short-term graded running performance is affected by a hypobaric hypoxic environment (simulated 2,500 m) (H). Seven male middle-distance runners performed an aerobic performance test and an intermittent short-term graded anaerobic running-performance test (MART) both in H and in a normobaric normoxic environment (N). VO_2max and OBLA were markedly lower (by 18.1% and 8.7%, respectively) in H than in N. In MART, neither maximal running velocity (V_max) nor exhaustion-time was different between N and H (454 (7) m min^–1 vs. 451 (6) m min^–1, respectively, and 208.7 (5.2) s vs. 205.7 (4.2) s, respectively). The blood lactate concentration at sub-maximal running speed (425 m min^–1) was significantly greater in H than in N (paired t-test: P<0.05). These results suggest that, in trained middle-distance runners, intermittent short-term graded running performance is not affected by H, despite a considerable decrease in aerobic power in H during the aerobic performance test.