Variation in heart rate and blood lactate concentration in freestyle kytesurfing

AIM

The aim of this paper was to evaluate the physiological demands of freestyle kitesurfing.

METHODS

Ten elite subjects performed an incremental running test on a treadmill and a three 7 min simulated freestyle heats of kitesurfing in MW (Midwind) condition ranging from 15 to 22 knots. Oxygen uptake (VO(2)) was estimated from the heart rate (HR) recorded during the freestyle trial using the individual HR-VO(2) relationship determined during the incremental test. Blood lactate concentration [Lab] was measured at rest and 3 min after the exercise completion. 3 experienced kitesurfers acted as judges to better simulate competition conditions.

RESULTS

Linear relationship was demonstrated between scores and % HR(max) on water (r=-0.764, P<0.05), HR(max) on water (r=-0.684, P<0.05) estimated VO(2) on water (r=-0.724, P<0.05), HR on water (r=0.709, P<0.05), % VO(2) on water (r=0.740, P<0.05), final [Lab] (r=-0.884, P<0.05), anaerobic threshold (AT) (r=0.836, P<0.05), HR in AT (r=0.748, P<0.05) and ranking (r=-0,924, P<0.05), mean HR and estimated VO(2) values represented, respectively 85.4±3.0% of maximal heart rate and 80.0±4.5% of maximal oxygen uptake. Mid values for [Lab] were observed at the end of crossing trial (5.2±0.8 mmol L(-1)).

CONCLUSION

This first analysis of freestyle kitesurfing suggests that the energy demand is sustained by both aerobic and anaerobic metabolism during a MW condition and freestyle event of kitesurfing.

Assessment of physiological demand in kitesurfing

To evaluate the physiological demands of kitesurfing, ten elite subjects performed an incremental running test on a 400-m track and a 30-min on-water crossing trial during a light crosswind (LW, 12-15 knots). Oxygen uptake (V(O)(2)) was estimated from the heart rate (HR) recorded during the crossing trial using the individual HR-V(O)(2) relationship determined during the incremental test. Blood lactate concentration [La(b)] was measured at rest and 3 min after the exercise completion. Mean HR and estimated V(O)(2) values represented, respectively 80.6 +/- 7.5% of maximal heart rate and 69.8 +/- 11.7% of maximal oxygen uptake for board speeds ranging from 15 to 17 knots. Low values for [La(b)] were observed at the end of crossing trial (2.1 +/- 1.2 mmol l(-1). This first analysis of kitesurfing suggests that the energy demand is mainly sustained by aerobic metabolism during a LW condition.

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.

Variable power output during cycling improves subsequent treadmill run time to exhaustion

The aim of this study was to investigate the effect of constant versus variable power output cycling exercise on subsequent high-intensity, running performance. Eight triathletes completed two testing sessions (in a random order), which required the subjects to perform 30 min of cycling at either, a constant power output (90% of the lactate threshold), or a variable power output with power output alternating every 5 min (+/-20% of the constant workload). Each cycling bout was immediately followed by a high-intensity treadmill run (16.7+/-0.7 km h(-1)) to exhaustion. No significant differences were found for mean metabolic values or power output between cycling conditions. However, a significant (P<0.05) improvement in run time to exhaustion was reported after 30 min of variable cycling (15:09+/-4:43 min) compared to constant cycling (10:51+/-3:32 min). The results of this study demonstrate that, despite similar average physiological responses during 30 min of cycling, variable-intensity cycling results in an improved running performance compared to constant-intensity cycling. It is hypothesised that the reduced power output in the final 5 min of variable cycling protocol may allow recovery before transition, however the mechanisms involved cannot be determined from the current study.

Cadence selection affects metabolic responses during cycling and subsequent running time to fatigue

OBJECTIVES

To investigate the effect of cadence selection during the final minutes of cycling on metabolic responses, stride pattern, and subsequent running time to fatigue.

METHODS

Eight triathletes performed, in a laboratory setting, two incremental tests (running and cycling) to determine peak oxygen uptake (VO2PEAK) and the lactate threshold (LT), and three cycle-run combinations. During the cycle-run sessions, subjects completed a 30 minute cycling bout (90% of LT) at (a) the freely chosen cadence (FCC, 94 (5) rpm), (b) the FCC during the first 20 minutes and FCC-20% during the last 10 minutes (FCC-20%, 74 (3) rpm), or (c) the FCC during the first 20 minutes and FCC+20% during the last 10 minutes (FCC+20%, 109 (5) rpm). After each cycling bout, running time to fatigue (Tmax) was determined at 85% of maximal velocity.

RESULTS

A significant increase in Tmax was found after FCC-20% (894 (199) seconds) compared with FCC and FCC+20% (651 (212) and 624 (214) seconds respectively). VO2, ventilation, heart rate, and blood lactate concentrations were significantly reduced after 30 minutes of cycling at FCC-20% compared with FCC+20%. A significant increase in VO2 was reported between the 3rd and 10th minute of all Tmax sessions, without any significant differences between sessions. Stride pattern and metabolic variables were not significantly different between Tmax sessions.

CONCLUSIONS

The increase in Tmax after FCC-20% may be associated with the lower metabolic load during the final minutes of cycling compared with the other sessions. However, the lack of significant differences in metabolic responses and stride pattern between the run sessions suggests that other mechanisms, such as changes in muscular activity, probably contribute to the effects of cadence variation on Tmax

Effect of cycling cadence on subsequent 3 km running performance in well trained triathletes

OBJECTIVES

To investigate the effect of three cycling cadences on a subsequent 3000 m track running performance in well trained triathletes.

METHODS

Nine triathletes completed a maximal cycling test, three cycle-run succession sessions (20 minutes of cycling + a 3000 m run) in random order, and one isolated run (3000 m). During the cycling bout of the cycle-run sessions, subjects had to maintain for 20 minutes one of the three cycling cadences corresponding to 60, 80, and 100 rpm. The metabolic intensity during these cycling bouts corresponded approximately to the cycling competition intensity of our subjects during a sprint triathlon (> 80% VO(2)max).

RESULTS

A significant effect of the prior cycling exercise was found on middle distance running performance without any cadence effect (625.7 (40.1), 630.0 (44.8), 637.7 (57.9), and 583.0 (28.3) seconds for the 60 rpm run, 80 rpm run, 100 rpm run, and isolated run respectively). However, during the first 500 m of the run, stride rate and running velocity were significantly higher after cycling at 80 or 100 rpm than at 60 rpm (p<0.05). Furthermore, the choice of 60 rpm was associated with a higher fraction of VO(2)max sustained during running compared with the other conditions (p<0.05).

CONCLUSIONS

The results confirm the alteration in running performance completed after the cycling event compared with the isolated run. However, no significant effect of the cadence was observed within the range usually used by triathletes.

Influence of drafting during swimming on ratings of perceived exertion during a swim-to-cycle transition in well-trained triathletes

After the swim to cycle transition of a triathlon, perceived exertion (RPE) during cycling was higher than during a single cycling bout for 8 well-trained triathletes, but swimming in a drafting position led to lower RPE responses and energy cost of cycling than swimming alone.

Influence of physical exercise on perceptual response in aerobically trained subjects

A significant effect of fatigue induced byphysical exercise leading to exhaustion was observed for 6 male triathletes using some specific analysis of the critical flicker fusion test.

Single and choice reaction time during prolonged exercise in trained subjects: influence of carbohydrate availability

The aim of the present study was to examine the effects of prolonged exercise at the ventilatory threshold and carbohydrate ingestion on single (SRT) and choice (CRT) reaction time. Eight well-trained triathletes completed three testing sessions within a 3-week period. Maximal oxygen uptake was determined in the first test, whereas the second and the third sessions were composed of a 100-min run (treadmill 15 min, overground 70 min, treadmill 15 min) performed at the velocity associated with the ventilatory threshold. During these submaximal tests, the subjects ingested (in random order) 8 ml x kg(-1) body weight of either a placebo (Pl) or 5.5% carbohydrate (CHO) solution prior to the first submaximal run and 2 ml x kg(-1) body weight every 15 min after that. The cognitive tasks were performed before and after exercise for CRT, and before, during each submaximal run and after exercise for SRT. Furthermore, at the end of each submaximal test subjects were asked to report their rating of perceived exertion (RPE). Results showed a significant positive effect of CHO ingestion on RPE and CRT performance at the end of exercise, while no effect of exercise duration was found in the Pl condition. After a 100-min run, during the CHO condition, CRT mean (SD) group values decreased from 688.5 (51) ms to 654 (63) ms, while during the Pl condition, RPE mean group values increased from 11 (2) to 16 (1.02) and CRT mean values remained stable [688 (104) ms vs 676 (73.4) ms, P > 0.05]. No similar effect was observed for SRT. These results suggest that CHO-electrolyte ingestion during a 100-min run results in an improvement in the complex cognitive performance measured at the end of that run.

Effect of exercise duration on optimal pedaling rate choice in triathletes

The purpose of this study was to investigate the effect of an exercise duration similar to triathlon's cyclism event (approximately 1 hr), on factors determining the freely chosen cadence. Nine trained triathletes completed a cycling track session conducted at a speed corresponding to 75% of maximal heart rate. This session was composed of five submaximal rides performed at five cadences presented in a random order (65, 80, 95, 110 rpm and freely chosen cadence) realized before and after a 1-hr exercise at the freely chosen cadence. Results show, during the first condition, that triathletes choose spontaneously a cadence (90,1 +/- 10,7 rpm) close to the neuromuscular optimum (89,6 +/- 1,1 rpm) while at the end of exercise, a decrease of the freely chosen cadence (82,8 +/- 8,7 rpm) was observed toward the energetically optimal cadence (78,6 +/- 5,8 rpm). These findings suggest the hypothesis of an adaptation of the movement pattern with the exercise duration in order to minimize the energy cost rather than the neuromuscular cost of cycling.

Carbohydrate ingestion does not influence the change in energy cost during a 2-h run in well-trained triathletes

The aim of this study was to examine whether the increase in the energy cost of running (C(r)), previously reported to occur at the end of a prolonged run, could be influenced by the ingestion of either an artificially sweetened placebo (Pl) or a 5.5% carbohydrate (CHO) solution. Ten well-trained triathletes completed three testing sessions within a 3-week period. The aim of the first session was to determine maximal oxygen uptake (VO(2)(max)) and the velocity associated with ventilatory threshold (nu(VT)). The second and the third sessions were composed of two submaximal treadmill runs (20 min long, 0% grade, performed at nu(VT)), before and after an 80-min overground run, also conducted at nu(VT). During these submaximal tests, the subjects ingested (in a random order) either a Pl or CHO solution prior to the first submaximal run and every 20 min after that. During the first session, ventilatory threshold (VT) occurred at [mean (SD)] 81.2 (2.5)% VO(2)(max) and 16.5 (0.6) km. h(-1). A significant effect of exercise duration was found on C(r) (DeltaC(r)) at the end of the run, whatever the solution ingested (DeltaC(r) = 5.7% and 7.01% for CHO and Pl, respectively). A reduction in the respiratory exchange ratio (from 0.98 to 0.90) was observed only at the end of the Pl trial. In this study, C(r) seems to be affected only to a minor extent by substrate turnover. Moreover, the increase in the demand for oxygen, estimated from the increase in ventilation, accounted for only a minor proportion of the increase in C(r) (11% and 17% for CHO and Pl, respectively). No correlation was found between the changes in C(r) and the changes in the other physiological parameters recorded. These results suggest, indirectly, that C(r) increases during a 2-h run at 80% VO(2)(max) in well-trained subjects can be explained mainly by alterations in neuromuscular performance, which lead to a decrease in muscle efficiency.

Energetically optimal cadence vs. freely-chosen cadence during cycling: effect of exercise duration

The purpose of this study was to examine the relationship between cadence and oxygen consumption with exercise duration. Ten triathletes who trained regularly were examined. The first test was always a maximal test to determine maximal oxygen uptake (VO2max). The other sessions were composed of six submaximal tests representing 80% of the maximal power reached with VO2max (Pmax). During these tests submaximal rides with a duration of 30 min were performed. Each test represented, in a randomised order, one of the following pedal rates: 50, 65, 80, 95, 110 rpm and a freely-chosen rate. VO2, respiratory parameters, and heart rate were monitored continuously. Two periods, between the 3rd and the 6th minute and between the 25th and the 28th minute, were analysed. Results showed that when VO2 and heart rate were plotted against cadence, each curve could be best described by a parabolic function, whatever the period. Furthermore, a significant effect of period was found on energetically optimal cadence (70 +/- 4.5 vs. 86 +/- 6.2 rpm, P < 0.05). Only during the second period was no significant difference found between freely-chosen cadence (83 +/- 6.9 rpm) and energetically optimal cadence (P > 0.05). In conclusion, our results suggest that during prolonged exercise triathletes choose a cadence that is close to the energetically optimal cadence. A change of muscle fibre recruitment pattern with exercise duration and cadence would explain the shift in energetically optimal rate towards a higher pedal rate observed at the end of exercise.