Relationship between strength level and pedal rate

The purpose of this study was to examine the relationship between strength capacity and preferred and optimal cadence in well trained cyclists. Eighteen cyclists participated in this study. Each subject completed three sessions. The initial session was to evaluate the maximal isokinetic voluntary contraction level of lower limb. The second session was an incremental test to exhaustion. During the third session subjects performed a constant cycling exercise (20 min) conducted at five randomly cadences (50, 70, 90, 110 rpm) and at the preferred cadence (FCC) at the power reached at ventilatory threshold. Cardiorespiratory and EMG values were recorded. A metabolic optimum (EOC) was observed at 63.5 +/- 7.8 rpm different from preferred cadence (FCC, 90.6 +/- 9.1 rpm). No difference was found between FCC and the neuromuscular optimal cadence (NOC, 93.5 +/- 4). Significant relationships were found between EOC, NOC and strength capacities (r = - 0.75 and - 0. 63), whereas FCC was only related with VO2max (r = 0.59). The main finding of this study was that during submaximal cycling energetically optimal cadence or neuromuscular optimum in trained cyclists was significantly related with strength capacity and whereas preferred cadence seems to be related with endurance training status of cyclists.     

Effets d'une complémentation nutritionnelle en vitamines et minéraux sur la chute de force et les marqueurs biologiques consécutifs à un exercice excentrique chez des personnes âgées

Purpose

The effects of vitamins and minerals complex supplementation on maximal voluntary contraction decrease (FMV) and biological markers following an eccentric exercise at old people.

Method

Sixteen elderly subjects took either placebo (Pl group) or vitamins and minerals (Isoxan Senior, NHS, Rungis, France) (group S) for 21 d before an eccentric exercise and for 3 d after the exercise. The FMV and surface EMG activity (RMS) of the vastus lateralis (VL), vastus médialis (VM) and rectus fémoris (RF) were recorded before (Pre), immediately after (Post), 24 h (Post 24) and 48 h (Post 48) after the exercise. CCVThe creatine kinase (CK), lactate déshydrogénase, malondialdéhyde, and tumor necrosis Factor (TNFα) levels were analyzed.

Results

The reduced MVC (S: 11,2 ± 4,8%; Pl: 17,8 ± 10,4%, P < 0,01) after exercise was associated with a significant reduction in RMS VL, RMS VM and RMS RF values for both groups. A faster FMV recovery appeared at 48 h for the S group (P < 0.05). CK and TNFα values increased in post-exercise.

Conclusion

A dietary supplementation of a vitamin and mineral complex does not attenuate the loss of contractile function immediately after the running exercise, and it may accelerate the recovery of maximal force capacity after 48 h by limiting the post-exercise pro-inflammatory processes.     

Age-related changes in cardio-respiratory responses and muscular performance following an Olympic triathlon in well-trained triathletes

The aim of the present study was to compare the maximal isometric torque and cardio-respiratory parameters in well-trained young and master triathletes prior to and following an Olympic distance triathlon. One day before and 24 h following the event, participants performed three maximum voluntary isometric knee extensions and flexions and an incremental running test on a treadmill to determine the maximal isometric torque, maximal oxygen uptake ( [(V)\dot]\textO_2max ) \left( {\dot{V}{\text{O}}_{2\max } } \right) , speed at [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } (vVO₂max), speed at ventilatory thresholds (VT1 and VT2) and submaximal running economy. Prior to the event [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } , vVO₂max, speed at ventilatory thresholds and running economy were significantly lower in master athletes, but maximal voluntary torque was similar between the groups. 24 h following the race, a similar significant decrease in [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } (−3.1% in masters, and −6.2% in young, p < 0.05), and vVO₂max (−9.5% in masters, and −5.6% in young, p < 0.05) was observed in both the groups. The speed at VT2 significantly decreased only in master athletes (−8.3%, p < 0.05), while no change was recorded in maximal voluntary torque or submaximal running economy following the event. The results indicate that for well-trained subjects, the overall relative exercise intensity during an Olympic distance triathlon and the fatigue 24 h following the event seem to be independent of age.     

Determination of the Most Influential Sources of Variability in Tacrolimus Trough Blood Concentrations in Adult Liver Transplant Recipients: A Bottom-Up Approach

Tacrolimus, an immunosuppressant drug, presents a narrow therapeutic window and a large pharmacokinetic variability with poor correlation between drug dosing regimen and blood concentration. The objective was to identify predictive factors influencing tacrolimus trough concentrations (C0) using a bottom-up approach. A physiologically based pharmacokinetic (PBPK) model of tacrolimus was proposed, taking into account the body weight, the proportion of fat (P _fat), hematocrit, lipid fraction of organs, typical intrinsic clearance (CLi_typ), CYP3A5 genotype of liver donor, plasma unbound fraction of tacrolimus (fu_p), and concomitant drugs (CYP3A4 inhibitors). For the evaluation of the PBPK model, mean C0 and concentrations 2 h after oral dose of tacrolimus were compared with those from 66 liver transplant recipients included in a multicentric pharmacokinetic study and were found very close. Tacrolimus concentration profiles were simulated in a virtual population defined by a set of covariate values similar to those from the real population. The sensitivity of tacrolimus C0 with respect to each covariate has been tested to identify the most influential ones. With the range of covariate values tested, the impact of each covariate on tacrolimus C0 may be ranked as follows: fu_p, CLi_typ, bioavailability, body weight, hematocrit, CYP3A5 polymorphism, P _fat, and CYP3A4 inhibitory drug–drug interactions. Values for initial dosing regimen of tacrolimus in order to reach a C0 of 10 ng/ml at day 5 (assuming a constant dosing schedule) as a function of CYP3A5 donor genotype and patient’s hematocrit and body weight are proposed.     

Postexercise cooling interventions and the effects on exercise-induced heat stress in a temperate environment

The aim of this study was to examine the effects of cool water immersion (20 °C; CWI) while wearing a cooling jacket (Cryovest;V) and a passive control (PAS) as recovery methods on physiological and thermoregulatory responses between 2 exercise bouts in temperate conditions. Nine well-trained male cyclists performed 2 successive bouts of 45 min of endurance cycling exercise in a temperate environment (20 °C) separated by 25 min of the respective recovery interventions. Capillary blood samples were obtained to measure lactate (La?), sodium (Na?), bicarbonate (HCO??) concentrations and pH, whilst body mass loss (BML), core temperature (T(core)), skin temperature (T(skin)), heart rate (HR), oxygen uptake , and minute ventilation were measured before (Pre), immediately after the first exercise bout (Ex1), the recovery (R), and after the second exercise bout (Ex2). V and CWI both resulted in a reduction of T(skin) at R (-2.1 ± 0.01 °C and -11.6 ± 0.01 °C, respectively, p < 0.01). Despite no difference in final values post-Ex2 (p > 0.05), V attenuated the rise in HR, minute ventilation, and oxygen uptake from Ex1 to Ex2, while T(core) and T(skin) were significantly lower following the second session (p < 0.05). Further, CWI was also beneficial in lowering T(core), T(skin), and BML, while a rise in Na? was observed following Ex2 (p < 0.05). Overall results indicate that cooling interventions (V and CWI) following exercise in a temperate environment provide a reduction in thermal strain during ensuing exercise bouts.     

Effects of acute physical exercise characteristics on cognitive performance

The effect of physical exercise on mental function has been widely studied from the beginning of the 20th century. However, the contradictory findings of experimental research have led authors to identify several methodological factors to control in such studies including: (i) the nature of the psychological task; and (ii) the intensity and duration of physical exercise. The purpose of this article is to provide information, from the perspective of performance optimisation, on the main effects of physical task characteristics on cognitive performance. Within this framework, some consistent results have been observed during the last decade. Recent studies, using mainly complex decisional tasks, have provided the research community with clear support for an improvement of cognitive performance during exercise. Diverse contributing factors have been suggested to enhance cognitive efficacy. First, an increase in arousal level related to physical exertion has been hypothesised. Improvement in decisional performance has been observed immediately after the adrenaline threshold during incremental exercise. Such positive effects could be enhanced by nutritional factors, such as carbohydrate or fluid ingestion, but did not seem to be influenced by the level of fitness. Second, the mediating role of resource allocation has been suggested to explain improvement in cognitive performance during exercise. This effect highlights the importance of motivational factors in such tasks. Finally, when the cognitive performance was performed during exercise, consistent results have indicated that the dual task effect was strongly related to energetic constraints of the task. The greater the energy demand, the more attention is used to control movements.     

Influence of cycling cadence on subsequent running performance in triathletes

PURPOSE: The purpose of this study was to investigate the influence of different cycling cadences on metabolic and kinematic parameters during subsequent running. METHODS: Eight triathletes performed two incremental tests (running and cycling) to determine maximal oxygen uptake (VO2max) and ventilatory threshold (VT) values, a cycling test to assess the energetically optimal cadence (EOC), three cycle-run succession sessions (C-R, 30-min cycle + 15-min run), and one 45-min isolated run (IR). EOC, C-R, and IR sessions were realized at an intensity corresponding to VT + 5%. During the cycling bouts of C-R sessions, subjects had to maintain one of the three pedaling cadences corresponding to the EOC (72.5 +/- 4.6 rpm), the freely chosen cadence (FCC; 81.2 +/- 7.2 rpm), and the theoretical mechanical optimal cadence (MOC, 90 rpm; Neptune and Hull, 1999). RESULTS: Oxygen uptake (VO2) increased during the 30-min cycling only at MOC (+12.0%) and FCC (+10.4%). During the running periods of C-R sessions, VO2, minute ventilation, and stride-rate values were significantly higher than during the IR session (respectively, +11.7%, +15.7%, and +7.2%). Furthermore, a significant effect of cycling cadence was found on VO2 variability during the 15-min subsequent run only for MOC (+4.1%) and FCC (+3.6%). CONCLUSION: The highest cycling cadences (MOC, FCC) contribute to an increase in energy cost during cycling and the appearance of a VO2 slow component during subsequent running, whereas cycling at EOC leads to a stability in energy cost of locomotion with exercise duration. Several hypotheses are proposed to explain these results such as changes in fiber recruitment or hemodynamic modifications during prolonged exercise.     

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.