Estimation of oxygen cost of internal power during cycling exercise with changing pedal rate

It has been reported that oxygen uptake (VO2) increases exponentially with levels of the pedal rate during cycling. The purpose of this study was therefore to test the hypothesis that the O2 cost for internal power output (Pint) exerted in exercising muscle itself would be larger than for an external power output (Pext) calculated from external load and pedal rate during cycling exercise under various conditions of Pint and Pext in a large range of pedal rates. The O2 cost (DeltaVO2/ Deltapower output) was investigated in three experiments that featured different conditions on a cycle ergometer that were carried out at the same levels of total power output (Ptot; sum of Pint and Pext) (Exp. 1), Pext (Exp. 2) and load (Exp. 3). Each experiment consisted of three exercise tests with three levels of pedal rate (40 rpm for a lower pedal rate: LP; 70-80 rpm for a moderate pedal rate: MP; and 100-120 rpm for a higher pedal rate: HP) lasting for 2-3 min of unloaded cycling followed by 4-5 min of loaded cycling. Blood lactate accumulations (2.3-3.4 mmol l(-1)) at the HP were significantly higher compared with the LP (0.6-0.9 mmol l(-1)) and MP (0.9-1.0 mmol l(-1)) except for the LP in Exp. 1. The VO2 (360-432 ml min(-1) for LP, 479-644 ml min(-1) for MP, 960-1602 ml min(-1) for HP) during unloaded cycling in the three experiments increased exponentially with increasing pedal rates regardless of Pext=0. Moreover, the slope of the VO2-Pint (13.7 ml min(-1) W(-1)) relation revealed a steeper inclination than that of the VO2-Pext (10.2 ml min(-1) W(-1)) relation. We concluded that the O2 cost for Pint was larger than for Pext during the cycling exercises, indicating that the O2 cost for Ptot could be affected by the ratio of Pint to Ptot due to the levels of pedal rate.     

Pacing pattern in a 30-minute maximal cycling test

The purpose of this study was to investigate the pacing pattern and associated physiological effects in competitive cyclists who performed a 30-minute maximal cycling test. Measurements included oxygen uptake (V O2), heart rate (HR), blood lactate concentration (BLC), rating of perceived exertion (RPE), and work rate in watts. Twelve well-trained amateur cyclists (seven men and five women) whose mean age was 32.4 +/- 8.6 years participated in this study. They performed a 30-minute self-paced maximal cycling test using their own performance road bike attached to a CompuTrainer Pro, which allowed the assessment of work rate (W). During the test, work rate, V O2, and HR were measured every 30 seconds. Subjects' BLC and RPE were obtained every 5 minutes. Results indicate that no significant differences existed across three 10-minute periods for work rate, HR, or V O2. However, RPE at 30 minutes was significantly greater than RPE at 10 and 20 minutes (both p < 0.05). The RPE at 20 minutes was also greater than the RPE at 10 minutes (p < 0.01). Work rate remained relatively constant, with minimal fluctuations occurring throughout the test except for a surge during the final 30 seconds of the test. The associated V O2 was fairly constant over time, whereas HR rose linearly and gradually. It was concluded that pacing in a 30-minute maximal exercise bout performed in the laboratory in experienced cyclists varies minimally until the last 30 seconds. Knowledge of pacing strategy and the linked physiological responses may be helpful to exercise scientists in optimizing performance in the endurance athlete.     

Effect of duration and exogenous carbohydrate on gross efficiency during cycling

The purpose of this investigation was to determine the effects of 2.5 hours of cycling with and without carbohydrate supplementation on gross efficiency (GE). Trained cyclists (N = 15) were tested for V(.-)O2max (53.6 + 2.2 ml x kg(-1) x min(-1)) and lactate threshold during incremental tests to exhaustion. On 2 separate visits, cyclists performed 2.5 hours of cycling on an indoor trainer. A carbohydrate (C) or placebo (P) beverage was randomly provided and counterbalanced for each of the trials. Gross efficiency, cycling economy, power output, V(.-)O2, lactate, and blood glucose were measured every 20 minutes during the 2.5-hour ride. Muscle glycogen was measured immediately before and after the ride from the vastus lateralis. Results indicated that power output and V(.-)O2 decreased over time (p < 0.05) but were not different between trials. Relative GE and cycling economy during C were greater than P at 40 and 150 minutes (p < 0.05). Blood glucose significantly decreased in P and was lower than C at all time points (p < 0.05). Respiratory exchange ratio decreased over time in both trials, with a significant treatment effect at 40 and 150 minutes (p < 0.05). Muscle glycogen decreased by 65% during both conditions (p < 0.05) but demonstrated no treatment effect. We conclude that carbohydrate supplementation during 2.5 hours of cycling attenuated the decrease in GE possibly by maintaining blood glucose levels. This suggests that the positive effect of carbohydrate supplementation on endurance performance may be through the maintenance of metabolic efficiency.     

Deciphering the metabolic and mechanical contributions to the exercise-induced circulatory response: insights from eccentric cycling

Metabolic demand and muscle mechanical tension are closely coupled during exercise, making their respective drives to the circulatory response difficult to establish. This coupling being altered in eccentric cycling, we implemented an experimental design featuring eccentric vs. concentric constant-load cycling bouts to gain insights into the control of the exercise-induced circulatory response in humans. Heart rate (HR), stroke volume (SV), cardiac output (Q), oxygen uptake (V(.-)(O(2))), and electromyographic (EMG) activity of quadriceps muscles were measured in 11 subjects during heavy concentric (heavy CON: 270 +/- 13 W; V(.-)(O(2)) = 3.59 +/- 0.20 l/min), heavy eccentric (heavy ECC: 270 +/- 13 W, V(.-)(O(2)) = 1.17 +/- 0.15 l/min), and light concentric (light CON: 70 +/- 9 W, V(.-)(O(2)) = 1.14 +/- 0.12 l/min) cycle bouts. Using a reductionist approach, the circulatory responses observed between heavy CON vs. light CON (difference in V(.-)(O(2)) and power output) was ascribed either to metabolic demand, as estimated from heavy CON vs. heavy ECC (similar power output, different V(.-)(O(2))), or to muscle mechanical tension, as estimated from heavy ECC vs. light CON (similar V(.-)(O(2)), different power output). 74% of the Q response was determined by the metabolic demand, also accounting for 65% and 84% of HR and SV responses, respectively. Consequently, muscle mechanical tension determined 26%, 35%, and 16% of the Q, HR, and SV responses, respectively. Q was significantly related to V(.-)(O(2)) (r(2) = 0.83) and EMG activity (r(2) = 0.82; both P < 0.001). These results suggest that the exercise-induced circulatory response is mainly under metabolic control and support the idea that the level of muscle activation plays a role in the cardiovascular regulation during cycle exercise in humans.     

The prediction of maximal oxygen uptake before and after physical training in children.

Maximal oxygen consumption (V O2 max) expressed in ml/kg/min and predicted V O2 max were determined before and after 8 weeks of training in 24 boys 10-12 years. Training involved 13 of them while 11 were controls. Predicted V O2 max was based on submaximal cycling heart rate according to the Astrand-Rhyming procedure. Pre-training, V O2 max was underpredicted by 12 per cent. This resulted mainly from an apparently low cycling efficiency in these subjects compared to that implicit in the prediction equation. Although adjustments in the prediction equation could equalize the means for V O2 max and predicted V O2 max, the rather low correlation (r = .55) between these measures precluded the accurate prediction of individual scores. V O2 max remained unchanged with training while submaximal heart rate during bicycle and treadmill exercise showed a significant decrease, resulting in predicted increases in V O2 max in children. Since V O2 max was actually unchanged, the prediction falsely indicated an improvement. Furthermore, despite a significantly lower heart rate in the trained group, there was no difference in predicted V O2 max between the groups post-training. These findings indicate that if V O2 max is the parameter of interest, it would seem to be more satisfactory to measure it directly until more reliable methods of prediction are developed.     

Scientific approach to the 1-h cycling world record: a case study.

The purpose of this study was to describe the physiological and aerodynamic characteristics and the preparation for a successful attempt to break the 1-h cycling world record. An elite professional road cyclist (30 yr, 188 cm, 81 kg) performed an incremental laboratory test to assess maximal power output (W(max)) and power output (W(OBLA)), estimated speed (V(OBLA)), and heart rate (HR(OBLA)) at the onset of blood lactate accumulation (OBLA). He also completed an incremental velodrome (cycling track) test (VT1), during which V(OBLAVT1) and HR(OBLAVT1) were measured and W(OBLAVT1) was estimated. W(max) was 572 W, W(OBLA) 505 W, V(OBLA) 52.88 km/h, and HR(OBLA) 183 beats/min. V(OBLAVT1), HR(OBLAVT1), and W(OBLAVT1) were 52.7 km/h, 180 beats/min, and 500.6 W, respectively. Drag coefficient and shape coefficient, measured in a wind tunnel, were 0. 244 and 0.65 m(2), respectively. The cyclist set a world record of 53,040 m, with an estimated average power output of 509.5 W. Based on direct laboratory data of the power vs. oxygen uptake relationship for this cyclist, this is slightly higher than the 497. 25 W corresponding to his oxygen uptake at OBLA (5.65 l/min). In conclusion, 1) the 1-h cycling world record is the result of the interaction between physiological and aerodynamic characteristics; and 2) performance in this event can be predicted using mathematical models that integrate the principal performance-determining variables.     

Prior heavy exercise increases oxygen cost during moderate exercise without associated change in surface EMG.

The aim of this study was to test the hypothesis that prior heavy exercise results in a higher oxygen cost during a subsequent bout of moderate exercise due to changes in muscle activity. Eight male subjects (25+/-2 yr, +/-SE) performed moderate-moderate and moderate-heavy-moderate transitions in work rate (cycling intensity, moderate=90% LT, heavy=80% VO(2) peak). The second bout of moderate exercise was performed after 6 min (C) or 30s (D) of recovery. Pulmonary gas exchange was measured breath-by-breath and surface electromyography was obtained from the vastus lateralis and medialis muscles. Root mean square (RMS) and median power frequency (MDPF) were computed. Prior heavy exercise increased DeltaVO(2)/DeltaWR (C: +2.0+/-0.8 ml min(-1)W(-1), D: +3.4+/-0.8 ml min(-1)W(-1); P<0.05) and decreased exercise efficiency (C: -13.3+/-5.6%, D: -22.2 +/-4.9%; P<0.05) during the second bout of moderate exercise in the absence of changes in RMS. MDPF was slightly elevated ( approximately 2%) during the second bout of moderate exercise, but MDPF was not correlated with V O(2) (r=0.17). These findings suggest that the increased oxygen cost during moderate exercise following heavy exercise is not due to increased muscle activity as assessed by surface electromyography.     

维生素E和硒水平对肉鸡不同自由基代谢的影响

选用200羽14日龄健康AA肉鸡,以电子自旋共振(ESR)捕集法和生物化学法对肉仔鸡血液和组织器官的不同自由基进行直接或间接测定,探讨VE和Se对肉鸡不同自由基代谢的作用及其动态变化.结果表明:组织一氧化氮(NO)自由基水平随日粮VE含量升高而降低,二者呈负相关关系,日粮高水平Se有诱导产生NO自由基的倾向;高VE和Se日粮显著提高血清和肝脏中SOD和GSH-Px的活性,但随处理时间的延长,组织SOD活性逐渐降低,而GSH-Px活性逐渐升高,说明日粮VE和/或Se不足均会诱导机体产生O.2-、H2O2自由基,且O2.-自由基会持续大量产生,而H2O2自由基仅在缺乏初期大量产生,而后趋于缓和;低VE和/或低Se均显著提高组织MDA含量,且低Se比低VE更为显著.VE和Se对肉鸡NO、O.2-和H2O2自由基代谢的作用存在协同效应.     

The effects of ionized and nonionized compression garments on sprint and endurance cycling

ABSTRACT: Burden, RJ and Glaister, M. The effects of ionized and nonionized compression garments on sprint and endurance cycling. J Strength Cond Res 26(10): 2837-2843, 2012-The aim of this study was to examine the effects of ionized and nonionized compression tights on sprint and endurance cycling performance. Using a randomized, blind, crossover design, 10 well-trained male athletes (age: 34.6 ± 6.8 years, height: 1.80 ± 0.05 m, body mass: 82.2 ± 10.4 kg, V[Combining Dot Above]O2max: 50.86 ± 6.81 ml·kg·min) performed 3 sprint trials (30-second sprint at 150% of the power output required to elicit V[Combining Dot Above]O2max [pV[Combining Dot Above]O2max] + 3 minutes recovery at 40% pV[Combining Dot Above]O2max + 30-second Wingate test + 3 minutes recovery at 40% pV[Combining Dot Above]O2max) and 3 endurance trials (30 minutes at 60% pV[Combining Dot Above]O2max + 5 minutes stationary recovery + 10-km time trial) wearing nonionized compression tights, ionized compression tights, or standard running tights (control). There was no significant effect of garment type on key Wingate measures of peak power (grand mean: 1,164 ± 219 W, p = 0.812), mean power (grand mean: 716 ± 68 W, p = 0.800), or fatigue (grand mean: 66.5 ± 6.9%, p = 0.106). There was an effect of garment type on blood lactate in the sprint and the endurance trials (p < 0.05), although post hoc tests only detected a significant difference between the control and the nonionized conditions in the endurance trial (mean difference: 0.55 mmol·L, 95% likely range: 0.1-1.1 mmol·L). Relative to control, oxygen uptake (p = 0.703), heart rate (p = 0.774), and time trial performance (grand mean: 14.77 ± 0.74 minutes, p = 0.790) were unaffected by either type of compression garment during endurance cycling. Despite widespread use in sport, neither ionized nor nonionized compression tights had any significant effect on sprint or endurance cycling performance.     

Morning-to-evening differences in oxygen uptake kinetics in short-duration cycling exercise

This study analyzed diurnal variations in oxygen (O(2)) uptake kinetics and efficiency during a moderate cycle ergometer exercise. Fourteen physically active diurnally active male subjects (age 23+/-5 yrs) not specifically trained at cycling first completed a test to determine their ventilatory threshold (T(vent)) and maximal oxygen consumption (VO(2max)); one week later, they completed four bouts of testing in the morning and evening in a random order, each separated by at least 24 h. For each period of the day (07:00-08:30 h and 19:00-20:30 h), subjects performed two bouts. Each bout was composed of a 5 min cycling exercise at 45 W, followed after 5 min rest by a 10 min cycling exercise at 80% of the power output associated with T(vent). Gas exchanges were analyzed breath-by-breath and fitted using a mono-exponential function. During moderate exercise, the time constant and amplitude of VO(2) kinetics were significantly higher in the morning compared to the evening. The net efficiency increased from the morning to evening (17.3+/-4 vs. 20.5+/-2%; p<0.05), and the variability of cycling cadence was greater during the morning than evening (+34%; p<0.05). These findings suggest that VO(2) responses are affected by the time of day and could be related to variability in muscle activity pattern.     

Effect of recovery interval on multiple-bout sprint cycling performance after acute creatine supplementation

The purpose of this study was to examine the effect of varying recovery intervals on multiple-bout, short-duration, high-intensity cycling efforts of adult men supplemented with creatine (Cr) or a placebo (Pl). Thirty subjects underwent 3 trials of a maximal cycling protocol (T(0), T(1), T(2)). T(0) included V(O)2 max testing and familiarization with the sprint cycling protocol. T(1) consisted of 8 15-second bouts of sprint cycling exercise. Subjects were randomly assigned to recovery interval groups (1 minute, 3 minutes, 6 minutes), and Cr or Pl groups (0.3 g x kg(-1) x d(-1)). Posttesting (T(2)) took place 7 days after T(1) and consisted of an identical protocol as during T(1). Changes in mean power (MP), peak power (PP), and fatigue index (FI) were compared between trials. MP was significantly increased in Cr 1-minute, Cr 3-minute, and Pl 6-minute groups (p < 0.05). Significant PP increases were demonstrated in Cr 1-minute and Pl 6-minute groups (p < 0.05), and FI significantly increased in Pl 1-minute group (p < 0.05). Results indicate that Cr supplementation is effective in improving recovery from repeated sprint cycling performances when the recovery interval is of a short (<6 minutes) duration.     

Prior eccentric exercise reduces v[combining dot above]o2peak and ventilatory threshold but does not alter movement economy during cycling exercise

Exercise-induced muscle damage (EIMD) has been shown to reduce force production and result in delayed-onset soreness and pain in the damaged muscle(s). Cycling in the presence of EIMD reduces peak power output and time-trial performance. However, its effect on peak aerobic capacity has not been widely studied. The purpose of this study was to examine the impact of EIMD targeted specifically to the quadriceps muscle group on peak oxygen consumption (V[Combining Dot Above]O2peak) during cycling. Ten participants (4 men, 6 women) completed a V[Combining Dot Above]O2peak test on a cycle ergometer before and 48 hours after performing 24 eccentric contractions with their right and left quadriceps with a weight equal to 120% of 1-repetition maximal concentric strength (1RM). The EIMD was assessed using 1RM, and muscle soreness was assessed using a 100-mm visual analog scale. The presence of EIMD was confirmed by a 9% reduction in 1RM (p = 0.0001) and increased ratings of soreness from 2.4 ± 2.1 to 24.6 ± 10.8 mm (p = 0.001). The V[Combining Dot Above]O2peak was reduced from 46.2 ± 9.7 to 41.8 ± 10.7 ml·kg·min (10%; p = 0.01) with participants terminating exercise at lower heart rates 191 ± 9 vs. 186 ± 10 b·min (p = 0.02) and power output 248 ± 79 vs. 238 ± 81 W (p = 0.02) after EIMD. Additionally, ventilatory threshold decreased from 34.2 ± 7.8 to 30.5 ± 8.5 ml·kg·min (11%; p = 0.031). Despite the reduction in V[Combining Dot Above]O2peak, cycling economy (p = 0.17) did not differ pre-EIMD and post-EIMD. These findings indicate that EIMD reduced peak aerobic exercise capacity to an extent that could result in meaningful reductions in exercise performance. The reduction is likely attributable to a combination of reduced strength, earlier accumulation of lactic acid, and heightened muscle pain during exercise.     

Non-linear relationship between oxygen uptake and power output in the Astrand nomogram-old data revisited.

For the last decade there have been considerable discussion concerning the linearity / non-linearity of the oxygen uptake (V(O2)) - power output (W) relationship with strong experimental evidence of non-linearity provided mainly by breath-by-breath measurements. In this study, we attempted to answer the question whether the V(O2) - W relationship in the Astrand nomogram, as presented in the Textbook of Work Physiology, P.-O. Astrand et al. (2003), page 281, based on the Douglas bag method, is indeed linear, as stated by the authors before, or if a change point in V(O2), described by Zoladz et al. (1998) Eur J Appl Physiol 78: 369-377, can possibly be detected in those data. The V(O2) - W data were taken from the Astrand nomogram referenced above and from the Table 9.5 on page 282 in the same reference and tested for the presence of the change point in V(O2), using our two-phase model (see the reference above). In the first phase, a linear V(O2) - W relationship was assumed, whereas in the second one (above the so-called change point) an additional increase in V(O2) above the values expected from the linear model was allowed. It was found that in the data taken from the Astrand nomogram (data for men), as well as in the data taken from the Table 9.5, statistically significant change points in V(O2) were present at the power output of 150 W. The documentation of the presence of a change point in the V(O2) - W relationship in the Astrand data provides further evidence for the existence of a non-linearity in the V(O2) - W relationship in incremental exercise tests of humans, also in V(O2) data based upon the Douglas bag method.     

Salicylate inhibits LDL oxidation initiated by superoxide/nitric oxide radicals

Simultaneously produced superoxide/nitric oxide radicals (O2*-/NO*) could form peroxynitrite (OONO-) which has been found to cause atherogenic, i.e. oxidative modification of LDL. Aromatic hydroxylation and nitration of the aspirin metabolite salicylate by OONO- has been reported. Therefore we tested if salicylate may be able to protect LDL from oxidation by O2*-/NO* by scavenging the OONO reactive decomposition products. When LDL was exposed to simultaneously produced O2*-/NO* using the sydnonimine SIN-1, salicylate exerted an inhibitory effect on LDL oxidation as measured by TBARS and lipid hydroperoxide formation and alteration in electrophoretic mobility of LDL. The cytotoxic effect of SIN-1 pre-oxidised LDL to endothelial cells was also diminished when salicylate was present during SIN-1 treatment of LDL. Spectrophotometric analysis revealed that salicylate was converted to dihydroxybenzoic acid (DHBA) derivatives in the presence of SIN-1. 2,3- and 2,5-DHBA were even more effective to protect LDL from oxidation by O2*-/NO*. Because O2*-/NO* can occur in vivo, the results may indicate that salicylate could act as an efficacious inhibitor of O2*-/NO* initiated atherogenic LDL modification, thus further supporting the rationale of aspirin medication regarding cardiovascular diseases.     

Improved v[combining dot above]o2max and time trial performance with more high aerobic intensity interval training and reduced training volume: a case study on an elite national cyclist

ABSTRACT: St?ren, ?, Bratland-Sanda, S, Haave, M, and Helgerud, J. Improved V[Combining Dot Above]O2max and time trial performance with more high aerobic intensity interval training and reduced training volume: a case study on an elite national cyclist. J Strength Cond Res 26(10): 2705-2711, 2012-The present study investigated to what extent more high aerobic intensity interval training (HAIT) and reduced training volume would influence maximal oxygen uptake (V[Combining Dot Above]O2max) and time trial (TT) performance in an elite national cyclist in the preseason period. The cyclist was tested for V[Combining Dot Above]O2max, cycling economy (Cc), and TT performance on an ergometer cycle during 1 year. Training was continuously logged using heart rate monitor during the entire period. Total monthly training volume was reduced in the 2011 preseason compared with the 2010 preseason, and 2 HAIT blocks (14 sessions in 9 days and 15 sessions in 10 days) were performed as running. Between the HAIT blocks, 3 HAIT sessions per week were performed as cycling. From November 2010 to February 2011, the cyclist reduced total average monthly training volume by 18% and cycling training volume by 60%. The amount of training at 90-95% HRpeak increased by 41%. V[Combining Dot Above]O2max increased by 10.3% on ergometer cycle. TT performance improved by 14.9%. Cc did not change. In conclusion, preseason reduced total training volume but increased amount of HAIT improved V[Combining Dot Above]O2max and TT performance without any changes in Cc. These improvements on cycling appeared despite that the HAIT blocks were performed as running. Reduced training time, and training transfer from running into improved cycling form, may be beneficial for cyclists living in cold climate areas.     

Modulation of the rate of cardiac muscle contraction by troponin C constructs with various calcium binding affinities

We investigated whether changing thin filament Ca(2+) sensitivity alters the rate of contraction, either during normal cross-bridge cycling or when cross-bridge cycling is increased by inorganic phosphate (P(i)). We increased or decreased Ca(2+) sensitivity of force production by incorporating into rat skinned cardiac trabeculae the troponin C (TnC) mutants V44QTnC(F27W) and F20QTnC(F27W). The rate of isometric contraction was assessed as the rate of force redevelopment (k(tr)) after a rapid release and restretch to the original length of the muscle. Both in the absence of added P(i) and in the presence of 2.5 mM added P(i) 1) Ca(2+) sensitivity of k(tr) was increased by V44QTnC(F27W) and decreased by F20QTnC(F27W) compared with control TnC(F27W); 2) k(tr) at submaximal Ca(2+) activation was significantly faster for V44QTnC(F27W) and slower for F20QTnC(F27W) compared with control TnC(F27W); 3) at maximum Ca(2+) activation, k(tr) values were similar for control TnC(F27W), V44QTnC(F27W), and F20QTnC(F27W); and 4) k(tr) exhibited a linear dependence on force that was indistinguishable for all TnCs. In the presence of 2.5 mM P(i), k(tr) was faster at all pCa values compared with the values for no added P(i) for TnC(F27W), V44QTnC(F27W), and F20QTnC(F27W). This study suggests that TnC Ca(2+) binding properties modulate the rate of cardiac muscle contraction at submaximal levels of Ca(2+) activation. This result has physiological relevance considering that, on a beat-to-beat basis, the heart contracts at submaximal Ca(2+) activation.     

Impaired leg vasodilation during dynamic exercise in healthy older women.

The purpose of the present study was to test the hypothesis that leg blood flow responses during leg cycle ergometry are reduced with age in healthy non-estrogen-replaced women. Thirteen younger (20-27 yr) and thirteen older (61-71 yr) normotensive, non-endurance-trained women performed both graded and constant-load bouts of leg cycling at the same absolute exercise intensities. Leg blood flow (femoral vein thermodilution), mean arterial pressure (MAP; radial artery), mean femoral venous pressure, cardiac output (acetylene rebreathing), and blood O2 contents were measured. Leg blood flow responses at light workloads (20-40 W) were similar in younger and older women. However, at moderate workloads (50-60 W), leg blood flow responses were significantly attenuated in older women. MAP was 20-25 mmHg higher (P < 0.01) in the older women across all work intensities, and calculated leg vascular conductance (leg blood flow/estimated leg perfusion pressure) was lower (P < 0.05). Exercise-induced increases in leg arteriovenous O2 difference and O2 extraction were identical between groups (P > 0.6). Leg O2 uptake was tightly correlated with leg blood flow across all workloads in both subject groups (r2 = 0.80). These results suggest the ability of healthy older women to undergo limb vasodilation in response to submaximal exercise is impaired and that the legs are a potentially important contributor to the augmented systemic vascular resistance seen during dynamic exercise in older women.     

Electrically evoked and voluntary maximal isometric tension in relation to dynamic muscle performance in elderly male subjects, aged 69 years

The dynamic performance and electrically evoked mechanical properties of elderly triceps surae muscle have been investigated in 9 men, aged 69 yr. Dynamic performance consisted of cycling on a force bicycle and a vertical jump off two feet from a force platform. The results showed that the time to peak tension (TPT) and half relaxation time (1/2 RT) were significantly greater (p less than 0.001) by 30 ms and 22 ms and the supramaximal twitch (Pt) and tetanic (20 Hz-P020) tensions and maximal voluntary contraction (MVC) were less by 45 N (-33%), 708 N (-49%), and 899 N (-43%) in the elderly compared with young male control subjects. On the force platform, the height jumped (Ht), maximal force exerted (P), take-off velocity (VT), net impulse (NI) and peak power output (W) were less by 18.6 cm, 173 N, 0.9 ms-1, 52 Ns and 1120 w respectively. Similar differences of power, force and velocity were observed on the force bicycle. The reduction of W in the elderly was associated with the contractile characteristics of the leg muscle. The loss of contractile speed and capacity to to generate force in old people was reflected in their inability to develop power during the performance of a maximal vertical jump and cycling.