Cardiac electromechanical delay is increased during recovery from 40 km cycling but is not mediated by exercise intensity.

Cardiac electrical-mechanical delay (cEMD), left ventricular (LV) function, and cardiac troponin I (cTnI) were assessed after 40 km cycle time trials completed at high (HIGH) and moderate (MOD) intensities in 12 cyclists. Echocardiograms and blood samples were collected before, 10, and 60 min after cycling. cEMD as assessed by time from QRS onset to peak systolic (S') tissue velocity was lengthened after both bouts of cycling but was not mediated by cycling intensity (HIGH: 174 ± 52 vs 198 ± 26 ms; MOD: 151 ± 40 vs 178 ± 52 ms, P < 0.05). Global LV systolic function was unaltered by exercise. cEMD from QRS to peak early (E') diastolic tissue velocity was also increased post-exercise (HIGH: 524 ± 95 vs 664 ± 68 ms; MOD: 495 ± 62 vs 604 ± 91 ms, P < 0.05). Indices of LV diastolic function was reduced after cycling but were not mediated by exercise intensity. cTnI was elevated in two participants after HIGH trial (0.06 ug/L; 0.04 ug/L) and one participant after MOD trial (0.02 ug/L). While cEMD is lengthened and LV diastolic function was reduced post-cycling, altering time-trial intensity had little impact upon cEMD, LV function, and cTnI release.

The traditional maximal lactate steady state test versus the 5 × 2000 m test.

Here, we compared the maximal lactate steady state velocity (vMLSS) estimated from a single-visit protocol (v5×2000) to the traditional multi-day protocol (vMLSS). Furthermore, we determined whether there was a lactate steady state during the time limits (Tlim) at vMLSS or v5×2000. Eight runners completed a half marathon (HM), the traditional protocol to determine the vMLSS and the 5×2000 m test in a randomised order, and a Tlim at vMLSS and at v5×2000 in a randomised order. The vMLSS (13.56±0.90 km·h - 1) was higher than the v5×2000 (12.93±0.90 km·h - 1, p=0.001) and comparable to the vHM (13.34±0.75 km·h - 1). The vMLSS (r=0.83) and the v5×2000 (r=0.91) were associated with the vHM but were not indicative of the competition pace. The Tlim at vMLSS (64±15 min) was lower than the Tlim at v5×2000 (94±21 min) and the HM time (95±5 min). In both Tlim, lactate was lower at 45 min than upon finishing the effort and was predictive of its duration (p<0.05). Our results indicate that the 5×2000 m test can be equally useful to assess runners as the traditional MLSS protocol and that there is no lactate steady state during the Tlim at vMLSS or at v5×2000.

Cardiac biomarker response to intermittent exercise bouts.

The impact of intermittent exercise on cardiac biomarker release has not been clearly established. In experienced athletes, we examined the acute effect of a heavy resistance training session (n=18 males) and an indoor soccer match (n=21, 11 males, 10 females) on the release of cTnI, cTnT, and NT-proBNP. Biomarkers were assayed from blood samples collected at rest, immediately post- and at 1, 3, 6, 12, and 24 h post-exercise. The heavy resistance training session resulted in an increase in NT-proBNP (pre: 15 ± 17, peak post: 41 ± 56 ng L (-1); p=0.001) but not in cTnI (pre: 0.024 ± 0.009, peak post: 0.025 ± 0.011 µg L (-1), p=0.809) or cTnT (undetectable in all samples). The indoor soccer match led to an increase in the release of NT-proBNP (pre: 28 ± 32, peak post: 66 ± 56 ng L (-1); p=0.000) and cTnI (pre: 0.026 ± 0.047, peak post: 0.033 ± 0.051 µg L (-1); p=0.008) in both males and females but not cTnT (detectable in only one subject). The current data suggest that intermittent bouts of exercise result in only modest perturbations of cardiac biomarkers with very limited evidence of myocyte injury/insult.

The validity of incremental exercise testing in discriminating of physiological profiles in elite runners.

The goal of this study was to determine whether traditional ergoespirometric incremental exercise testing carried out to the point of exhaustion could be useful in distinguishing the physiological profiles of elite runners that compete in races that lasted about 8 minutes versus those that lasted about 2 hours. Ten male marathon runners (performance time: 2:12:04, coefficient of variation (CV) = 2.33%) and 8 male 3000 m steeplechase runners (performance time: 8:37.83, CV = 2.12%) performed an incremental test on the treadmill (starting speed 10 km·h-1; increments, 2 km·h-1; increment duration, 3 min to exhaustion). Heart rate (HR), VO2, and lactate concentrations were measured at the end of each exercise level. At maximal effort, there were no differences between the groups regarding VO2max and maximal HR; however, the workload time, vVO2max and peak treadmill velocity were significantly higher in the 3000 m steeplechase group (p<0.05). At submaximal effort, there were no significant differences between groups for VO2 (ml·kg-1·min-1), HR, or lactate. Our results show that this type of testing was not sufficient for discriminating the physiological profiles of elite runners who competed in middle-distance versus long-distance events (e.g. in the marathon and the 3000 m steeplechase).

The impact of exercise duration and intensity on the release of cardiac biomarkers.

Numerous studies have observed cardiac biomarker release with prolonged exercise. Despite this, we are unsure as to the constituent aspects of any given exercise bout that may be important in promoting cardiac biomarker release. This study examined the influence of exercise duration and intensity on the appearance of cardiac biomarkers. Twenty-one subjects ran for 45, 90 and 180 min at 85% and 95% of their individual anaerobic threshold on six different days randomized. Cardiac troponin I (cTnI) and N-terminal pro-brain natiuretic peptide (NT-proBNP) were assayed from blood samples collected before, 30 min and 3 h post-exercise. NT-proBNP was elevated after all exercise trials (range before: 21-32; range post: 38-67 ng/L). Peak post-exercise concentrations of NT-proBNP were associated with exercise duration (P=0.049), but not exercise intensity (P=0.451). cTnI was elevated after all exercise trials (range before: 0.007-0.011; range post: 0.008-0.021 µg/L). Peak post-exercise concentrations of cTnI were associated with exercise duration (P=0.003) and intensity (P=0.037). Data suggest that while both cTnI and NT-proBNP increased after all exercise trials, the mediating effect of duration influenced both NT-proBNP and cTnI while intensity influenced only cTnI.

Basic physiological measures determine fitness and are associated with running performance in elite young male and female Ethiopian runners.

AIM: The aim of this study was to determine if possible, with the resources available in Ethiopia, to make significant associations between racing performance and laboratory physiological test results in elite young African runners. METHODS: Twenty-four young Ethiopian runners (12 males and 12 females) attended the physiology laboratory of the Addis Ababa University, where skin fold thickness, basic resting pulmonary function and heart rate (HR) during an incremental treadmill exercise test were recorded a week before or a week after two official 800 and 1500 meter races. Performance was rated according to the scoring procedures of the International Association of Athletics Federations (IAAF): male runners (1041, CV=4.1%), female (1051, CV=2.8%). RESULTS: The sum of four skin folds was significantly correlated with male (r=-0.80, P<0.01) and female IAAF score (r= -0.78, P<0.01). IAAF score was also related to forced vital capacity (male: r=0.70, P<0.05; female: r=0.85, P<0.01) and forced expiratory volume in 1 s (male: r=0.63, P<0.05; female: r=0.80, P<0.01). For both sexes, HR at a fixed submaximal exercise workload was significantly associated with IAAF score. In both male and female runners, the more significant association was observed for a treadmill slope of 7.5% (r=-0.93, P<0.01; r= -0.95, P<0.01, respectively). CONCLUSIONS: These results show that basic physiological measures are useful in measuring fitness and in predicting middle-distance running performance in a homogeneous group of elite young male and female Ethiopian runners.