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Cycle Exercise (cycle + exercise)
Selected AbstractsThe decrease in electrically evoked force production is delayed by a previous bout of stretch,shortening cycle exerciseACTA PHYSIOLOGICA, Issue 1 2010S. Kamandulis Abstract Aim:, Unaccustomed physical exercise with a large eccentric component is accompanied by muscle damage and impaired contractile function, especially at low stimulation frequencies. A repeated bout of eccentric exercise results in less damage and improved recovery of contractile function. Here we test the hypotheses that (1) a prior stretch,shortening cycle (SSC) exercise protects against impaired muscle function during a subsequent bout of SSC exercise and (2) the protection during exercise is transient and becomes less effective as the exercise progresses. Methods:, Healthy untrained men (n = 7) performed SSC exercise consisting of 100 maximal drop jumps at 30 s intervals. The same exercise was repeated 4 weeks later. Peak quadriceps muscle force evoked by electrical stimulation at 15 (P15) and 50 (P50) Hz was measured before exercise, after 10, 25, 50 and 100 jumps as well as 1 and 24 h after exercise. Results:, P15 and P50 were higher during the initial phase of the repeated bout compared with the first exercise bout, but there was no difference between the bouts at the end of the exercise periods. P15 and P50 were again larger 24 h after the repeated bout. The P15/P50 ratio during exercise was not different between the two bouts, but it was higher after the repeated bout. Conclusion:, A prior bout of SSC exercise temporarily protects against impaired contractile function during a repeated exercise bout. The protection can again be seen after exercise, but the underlying mechanism then seems to be different. [source] Sex influence on myocardial function with exercise in adolescentsAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2010Thomas Rowland Objectives: Ventricular systolic functional response to exercise has been reported to be superior in adult men compared to women. This study explored myocardial responses to maximal upright progressive exercise in late pubertal males and females. Methods: Doppler echocardiographic techniques were utilized to estimate myocardial function response to a bout of progressive cycle exercise. Results: Systolic functional capacity, as indicated by ejection rate (12.5 ± 2.8 and 13.1 ± 1.0 [×10,2] ml s,1 cm,2 for boys and girls, respectively) and peak aortic velocity (208 ± 45 and 196 ± 12 cm s,1, respectively) at maximal exercise, did not differ between the two groups. Similarly, peak values as well as increases in transmitral pressure gradient (mitral E flow velocity), ventricular relaxation (tissue Doppler imaging E,), and left ventricular filling pressure (E/E, ratio) as estimates of diastolic function were similar in males and females. Conclusions: This study failed to reveal qualitative or quantitative differences between adolescent boys and girls in ventricular systolic or diastolic functional responses to maximal cycle exercise. Am. J. Hum. Biol. 22:680,682, 2010. © 2010 Wiley-Liss, Inc. [source] Left ventricular torsion and untwisting during exercise in heart transplant recipientsTHE JOURNAL OF PHYSIOLOGY, Issue 10 2009Ben T. Esch Left ventricular (LV) rotation is the dominant deformation during relaxation and links systole with early diastolic recoil. LV torsion and untwisting rates during submaximal exercise were compared between heart transplant recipients (HTRs), young adults and healthy older individuals to better understand impaired diastolic function in HTRs. Two dimensional and colour M-mode echocardiography with speckle-tracking analysis were completed in eight HTRs (age: 61 ± 9 years), six recipient age-matched (RM, age: 60 ± 11 years), and five donor age-matched (DM, age: 35 ± 8 years) individuals (all males) at rest and during submaximal cycle exercise. LV peak torsion, peak rate of untwisting and peak intraventricular pressure gradients (IVPGs) were examined. LV torsion increased with exercise in DMs (6.5 ± 5.6 deg, P < 0.05), but not in RMs (,2.6 ± 7.0 deg) or HTRs (,0.9 ± 4.4 deg). The change from rest to exercise in the peak rate of untwisting was significantly greater for DMs (,2.1 ± 0.5 rads s,1, P < 0.05) compared to RMs (,0.7 ± 1.3 rads s,1) and HTRs (,0.2 ± 0.9 rads s,1). The amount of untwisting occurring prior to mitral valve opening substantially declined with exercise in RMs and HTRs only. The change in IVPGs was 1.3-fold greater in DMs versus HTRs or RMs (P > 0.05). Peak LV torsion and untwisting are blunted during exercise in HTRs and RMs compared to DMs. These factors may contribute to the impaired diastolic filling found in HTRs during exercise. Similarities between HTRs and RMs during exercise suggest functional accelerated ageing of the cardiac allograft. [source] Mechanical ventilatory constraints during incremental cycle exercise in human pregnancy: implications for respiratory sensationTHE JOURNAL OF PHYSIOLOGY, Issue 19 2008Dennis Jensen The aim of this study was to identify the physiological mechanisms of exertional respiratory discomfort (breathlessness) in pregnancy by comparing ventilatory (breathing pattern, airway function, operating lung volumes, oesophageal pressure (Poes)-derived indices of respiratory mechanics) and perceptual (breathlessness intensity) responses to incremental cycle exercise in 15 young, healthy women in the third trimester (TM3; between 34 and 38 weeks gestation) and again 4,5 months postpartum (PP). During pregnancy, resting inspiratory capacity (IC) increased (P < 0.01) and end-expiratory lung volume decreased (P < 0.001), with no associated change in total lung capacity (TLC) or static respiratory muscle strength. This permitted greater tidal volume (VT) expansion throughout exercise in TM3, while preserving the relationship between contractile respiratory muscle effort (tidal Poes swing expressed as a percentage of maximum inspiratory pressure (PImax)) and thoracic volume displacement (VT expressed as a percentage of vital capacity) and between breathlessness and ventilation . At the highest equivalent work rate (HEWR = 128 ± 5 W) in TM3 compared with PP: , tidal Poes/PImax and breathlessness intensity ratings increased by 10.2 l min,1 (P < 0.001), 8.8%PImax (P < 0.05) and 0.9 Borg units (P < 0.05), respectively. Pulmonary resistance was not increased at rest or during exercise at the HEWR in TM3, despite marked increases in mean tidal inspiratory and expiratory flow rates, suggesting increased bronchodilatation. Dynamic mechanical constraints on VT expansion (P < 0.05) with associated increased breathlessness intensity ratings (P < 0.05) were observed near peak exercise in TM3 compared with PP. In conclusion: (1) pregnancy-induced increases in exertional breathlessness reflected the normal awareness of increased and contractile respiratory muscle effort; (2) mechanical adaptations of the respiratory system, including recruitment of resting IC and increased bronchodilatation, accommodated the increased VT while preserving effort,displacement and breathlessness, relationships; and (3) dynamic mechanical ventilatory constraints contributed to respiratory discomfort near the limits of tolerance in late gestation. [source] | ||||||||||