Progression of changes in left ventricular function during four days of simulated multi-stage cycling

Abstract

This study investigated the effect of multi-stage cycling on left ventricular function with optimal carbohydrate and fluid replacement. Eleven well-trained cyclists completed 4 days of 3 h race-simulated cycling at an average intensity of 51.8 ± 2.8 %W (max) with carbohydrate supplements (50 g h(-1)). Left ventricular function was assessed by conventional echocardiography and tissue-Doppler imaging before and immediately after exercise on each day and a final recovery measurement on day 5. The rate of passive ventricular filling was persistently suppressed during repeated days of strenuous cycling (change in Septal E' wave pre to post-exercise: -3.9 ± 3.2; -1.0 ± 1.7; -1.9 ± 2.1; -2.2 ± 2.4 cm s(-1) for day 1-4, respectively) and was not completely restored before the subsequent exercise bout. Ejection fraction was significantly reduced post-exercise on day 1 and 2 (by -6.3 ± 7.1 and -6.8 ± 7.6%, respectively), whereas the change was not significant on day 3 and 4 (-3.8 ± 8.5 and -5.5 ± 10.6%, respectively), and may be partly due to the augmented rate of late diastolic filling (Septal A' wave) noted only on day 3 and 4. Finally, resting end-diastolic volume on day 5 (recovery day) was increased compared to day 1 before exercise (127 ± 23 and 108 ± 25 ml, respectively) and may indicate secondary hypervolemia; induced to further compensate for the cardiovascular strain of multi-day exercise. Strenuous prolonged cycling even with carbohydrate replacement is sufficiently stressful to impair cardiac function. As a multi-day cycling event progresses, cardiovascular strain is mitigated by adaptations that assist in restoring systolic function, while diastolic function remains impaired.

Bone resorption is suppressed immediately after the third and fourth days of multiday cycling but persistently increased following overnight recovery

“…The average exercise intensity for all 4 days was similar, with a tendency for a lower intensity on day 3 compared with day 4 (p = 0.05) ( Table 2), as previously reported (Oosthuyse et al 2012). Consequently, total energy expenditure during exercise was similar on days 1, 2, and 4 but significantly less on day 3 than on days 2 and 4 (Table 2).…”

“…At least 2 weeks before the experimental trials, all cyclists completed a continuous incremental cycling test to exhaustion on the Lode Excalibur Sport cycling ergometer (Lode, Groningen, Netherlands) for the determination of maximal aerobic power output (W max ) and onset of blood lactate accumulation as the workload corresponding to the 4-mmol·L −1 blood lactate concentration, as previously described (Oosthuyse et al 2012). These variables are frequently reported when characterising cyclists (Faria et al 2005;Padilla et al 2008).…”

“…Serum osmolality was assessed by a calibrated osmometer by the method of vapour pressure depression (Vapro model 5600; Wescor, Logan, Utah, USA) and used to estimate changes in plasma volume from pre-to postexercise on each day. The serum osmolality data has been presented previously (Oosthuyse et al 2012). …”

“…Furthermore, prolonged, strenuous multiday cycling tends to induce secondary plasma volume expansion as the number of days progress (Oosthuyse et al 2012;Wirnitzer and Faulhaber 2007). For this reason, we corrected pre-exercise serum and plasma concentrations for days 2 to 4 using the equations described above where PV pre and [Osm] pre were always day 1 pre-exercise values and PV post and [Osm] post were replaced with pre-exercise values for days 2 to 4 to solve for the fractional ⌬PV each day pre-exercise relative to baseline (day 1 pre-exercise).…”

“…Interestingly, a comparison between days revealed that the pre-exercise cortisol concentration was significantly suppressed on days 2 to 4 compared with day 1 pre-exercise (p < 0.05). Consequently, the cortisol response to exercise (as post-minus pre-exercise values) was unchanged between days, despite a significantly lower absolute postexercise cortisol (Oosthuyse et al 2012). TEE, total energy expenditure; W max , power output as a percentage of maximal aerobic power; %W OBLA , power output as a percentage of the power output at the onset of blood lactate accumulation.…”