Abstract
tisport events continue to grow in popularity among recrea- tional, amateur, and professional athletes around the world. This study aimed to determine the compounding effects of the initial run and cycling legs of an International Triathlon Union (ITU) Duathlon simulation on maximal oxygen uptake (VO 2max), ventilatory threshold (VT) and running economy (RE) within a thermoneutral, laboratory controlled setting. Seven highly trained multisport athletes completed three trials; Trial-1 con- sisted of a speed only VO 2max treadmill protocol (SOVO 2max) to determine VO 2max, VT, and RE during a single-bout run; Trial-2 consisted of a 10 km run at 98% of VT followed by an incre- mental VO 2max test on the cycle ergometer; Trial-3 consisted of a 10 km run and 30 km cycling bout at 98% of VT followed by a speed only treadmill test to determine the compounding effects of the initial legs of a duathlon on VO 2max, VT, and RE. A re- peated measures ANOVA was performed to determine differ- ences between variables across trials. No difference in VO 2max, VT (%VO 2max), maximal HR, or maximal RPE was observed across trials. Oxygen consumption at VT was significantly lower during Trial-3 compared to Trial-1 (p = 0.01). This de- crease was coupled with a significant reduction in running speed at VT (p = 0.015). A significant interaction between trial and running speed indicate that RE was significantly altered during Trial-3 compared to Trial-1 (p < 0.001). The first two legs of a laboratory based duathlon simulation negatively impact VT and RE. Our findings may provide a useful method to evaluate multisport athletes since a single-bout incremental treadmill test fails to reveal important alterations in physiological thresholds. Key words: Multisport, sport performance, endurance, exercise
that RE was significantly altered during Trial-3 compared to Trial-1 (p < 0.001). The first two legs of a laboratory based duathlon simulation negatively impact VT and RE. Our findings may provide a useful method to evaluate multisport athletes since a single-bout incremental treadmill test fails to reveal important alterations in physiological thresholds. Key words: Multisport, sport performance, endurance, exercise prescription. Introduction The International Triathlon Union (ITU) serves as the governing body for all internationally sanctioned multi- sport events. These multisport competitions place a unique demand on athletes due to their need to perform a variety of sport modalities in a single event. Similarly, the coaches of these athletes have to manage acute and chron- ic training loads from a variety of modalities that further complicates the training model. Whether utilizing a tradi- tional periodization model or an alternative periodization model (Issurin, 2010), key physiological measures such as maximal oxygen uptake (VO2max), ventilatory threshold (VT), heart rate (HR), and blood lactate (BL) are often used to monitor, prescribe, and measure training related performance gains for endurance athletes (Bunc et al., 1995). While each of these periodization models have limitations (Issurin, 2010) they all aim to build fitness and ultimately increase athletic performance. Scientific research, and the presentation of this re- search to the public, plays an important role in progress- ing sport and the periodization methods in sport. Investi- gating the compounding effects of multisport events on athletic performance requires complex experimental de- signs with transitions from one modality to another. The compounding effects of the first two exercise bouts on the final run performance have become an increasingly popu- lar topic of research as the winner of a multisport event is often decided during the last leg of the competition (Landers et al., 2000; Vleck et al., 2006). De Vito et al. (1995) previously reported a decline in maximal oxygen uptake (VO2max) and VO2 (ml∙kg -1 ∙min -1 ) at VT during the final running leg of an ITU Triathlon simulation. De Vito et al. (1995) concluded that these declines could potential- ly influence performance during the last leg
competition (Landers et al., 2000; Vleck et al., 2006). De Vito et al. (1995) previously reported a decline in maximal oxygen uptake (VO2max) and VO2 (ml∙kg -1 ∙min -1 ) at VT during the final running leg of an ITU Triathlon simulation. De Vito et al. (1995) concluded that these declines could potential- ly influence performance during the last leg of a triathlon race and recommended that coaches and athletes consider this information when developing racing strategies. While triathlon and duathlon events have some similar charac- teristics, the physiological consequences associated with the transition phases may invoke different physiological responses. Few studies have investigated the effects of cycling on a subsequent running bout (Bernard et al., 2003; Gottschall and Palmer, 2000; Hue et al., 2000; Suriano et al., 2007) or running on subsequent cycling performance (Chapman et al., 2008; Gottschall and Palm- er, 2000; Suriano et al., 2007; Vercruyssen et al., 2002). The compounding effects of a duathlon event on running performance have been minimally investigated (Moncada-Jiménez et al., 2009; Sparks et al., 2005; 2013; Vallier et al., 2003). Both Moncada-Jiménez et al. (2009) and Sparks et al. (2013) investigated the effects of dietary modifications on duathlon performance. While both of these studies reported significant differences in carbohy- drate and fat metabolism between dietary modifications, neither found significant differences in overall time. Con- versely, Sparks et al. (2005) reported that carbohydrate and fat oxidation did not differ significantly between duathlon simulations performed at 10°C and 30°C. How- ever, they did report that overall performance was faster in the 10°C environment compared to 30°C. Vallier et al. (2003) investigated the energy cost of running during an outdoor duathlon simulation, reporting that the energy cost of running was not significantly different between the initial, and final, running bouts. Each of these studies provides unique and insightful information on duathlon performance. The external validity of Vallier et al. (2003) Research article Received: 15 December 2015 / Accepted: 16 February 2016 / Published (online): 23 May 2016
the initial, and final, running bouts. Each of these studies provides unique and insightful information on duathlon performance. The external validity of Vallier et al. (2003) Research article Received: 15 December 2015 / Accepted: 16 February 2016 / Published (online): 23 May 2016
Effect of a duathlon simulation on VT and RE 248 provides highly meaningful information about multisport performance to coaches and athletes alike, however, in- sight into the compounding effect of the first two legs of the duathlon event on performance during the final run- ning bout may have been limited by pacing strategy. While the physiological consequences of either a triathlon or duathlon event may be different due to the different transitional demands of each event, the alterations in final running performance observed during triathlon (De Vito et al., 1995) and duathlon (Vallier et al., 2003) simula- tions warrant further investigation. Thus, the purpose of this study was to further ex- pand on previous findings of duathlon performance by having athletes complete a duathlon simulation at the highest attainable intensity within a controlled laboratory setting. Specifically, our objective was to compare per- formance between a single-bout treadmill run and the final run of a duathlon simulation. Measures of maximal oxygen uptake (VO 2max), ventilatory threshold (VT), and running economy (RE) were used to assess differences between trials. We hypothesized that 1) VO 2peak would remain the same between Trial-1 and Trial-3 2) that VT would decrease, and 3) that RE would decrease during the final running bout of the duathlon simulation. Methods Subjects Seven highly- trained multisport male athletes (age: 34 ± 9 years; height: 1.78 ± 0.04 m; weight: 73.9 ± 2.7 kg) were recruited to participate in this study. Participants included professional and elite age-group athletes who had been training a minimum of fifteen hours per week for a mini- mum of six months prior to beginning the study. Prior to participating in the study, each subject was fully informed of the methodological procedures. This study was ap- proved by the Biomedical Institutional Review Board of the University of North Carolina at Chapel Hill. Partici- pants provided written consent before completing a phys- ical examination, medical history questionnaire, and a Par-Q (physical activity readiness questionnaire). Once participants were deemed healthy and low-risk (American College of Sports Medicine, 2010), they were scheduled for their first session. Overview Each athlete
proved by the Biomedical Institutional Review Board of the University of North Carolina at Chapel Hill. Partici- pants provided written consent before completing a phys- ical examination, medical history questionnaire, and a Par-Q (physical activity readiness questionnaire). Once participants were deemed healthy and low-risk (American College of Sports Medicine, 2010), they were scheduled for their first session. Overview Each athlete completed three testing sessions separated by a minimum of 72 hours and completed within a span of three weeks (Figure 1). Participants were asked to abstain from intense training 24 hours prior to each testing ses- sion. Trial- 1 consisted of a single incremental treadmill test to determine VO 2max. Trial-2 consisted of a 10 km run at VT proceeded by an incremental test on the cycle ergometer to determine VO 2max. During Trial-3, partici- pants performed a 10 km run and 30 km cycling bout at threshold before transitioning back to the treadmill to perform an incremental treadmill test to volitional exhaus- tion. Ergometers Incremental tests, as well as running and cycling bouts, were performed using the T2100 GE treadmill system (General Electric Company, USA) and Lode Corival electromagnetic breaking cycle ergometer (Lode B.V., Groningen, Netherlands). Athletes provided their saddle height (center of the bottom bracket to the top of the sad- dle) upon arrival at the lab for Trial- 2 and all settings were recorded and replicated in Trial-3. All athletes pro- vided their own clipless pedals; enabling them to wear their cycling shoes. Pre-trial measures and questionnaires Height and weight were recorded using a stadiometer (Perspective MO, USA) and Detecto 2381 balance beam scale (Detecto, Webb City, MO, USA) respectively. Prior to the start of each trial, urine specific gravity was as- sessed using a refractometer (TS Meter, American Optical Corp, Keene, NH, USA), to determine hydration status. In addition, adherence to pre-trial guidelines and prepar- edness was assessed using a questionnaire developed explicitly for this study. Specifically, the questionnaire asked about 24- hour exercise history and used 5-point Likert scales to assess fatigue and sleep quality. Individu- als reporting high levels of fatigue, poor or limited
Meter, American Optical Corp, Keene, NH, USA), to determine hydration status. In addition, adherence to pre-trial guidelines and prepar- edness was assessed using a questionnaire developed explicitly for this study. Specifically, the questionnaire asked about 24- hour exercise history and used 5-point Likert scales to assess fatigue and sleep quality. Individu- als reporting high levels of fatigue, poor or limited sleep quality or individuals with poor hydration status (Casa et al., 2000) were rescheduled for a later date. Determination of maximal oxygen uptake (VO 2max) and ventilatory threshold (VT) VO 2max and VT were determined from incremental proto- cols. To determine VO 2max during Trial-1 and Trial-3, the treadmill speed began at 8 km∙h -1 and the speed was in- creased 1.6 km/h each minute until a speed of 17.6 km/h. Beyond this point, incremental increases in speed were 0.8 km∙h -1 each minute until volitional exhaustion (Vanhoy, 2012). During Trial-2, participants completed an incremental test on a cycle ergometer. All participants started at 150 Watts and intensity increased 50 watts eve- ry two minutes until a workload of 250 watts was reached. After this, resistance increased by 30 watts every 2 minutes until volitional fatigue. Oxygen uptake, minute ventilation, and the respiratory exchange ratio were col- lected continuously with a Parvo Medics TrueMax® 2300 Metabolic system (Parvo Medics, Salt Lake City, UT, modified V-slope method (Sue et al., 1988) and by deter- mining the point corresponding to an increase in the Figure 1. Overview of study design.
Berry et al. 249 Table 1. Comparisons of maximal and submaximal values obtained during the three trials. Data are means (±SD). T1 T2 T3 VO 2max (ml∙kg -1 ∙min -1 ) 66.8 (6.1) 65.1 (5.0) 63.7 (7.0) BLmax 12.6 (2.5) 11.0 (2.0) 8.2 (2.1)* HRmax (bpm) 182 (10) 184 (11) 179 (10) RPEmax 19.1 (.7) 18.7 (1.0) 18.6 (.6) Max Running Speed (km∙h -1 ) 20.6 (1.4) - 18.7 (1.2)* VT (ml∙kg -1 ∙min -1 ) 50.6 (4.1) 50.8 (3.8) 47.0 (5.8)* VT (% VO 2max) 75.7 (3.5) 77.3 (6.9) 73.7 (5.6) RER (at VT) .90 (.03) .92 (.10) .84 (.04)* # RPE (at VT) 13.9 (1.1) 13.9 (1.3) 12.8 (1.6) Running Speed at VT (km∙h -1 ) 14.9 (1.3) - 13.5 (1.6)* HRavg (10 km run) - 163 (13) 159 (9) RPEavg (10 km run) - 13.5 (1.0) 13.0 (1.0) HRavg (30 km cycling) - - 153 (8) RPEavg (30 km cycling) - - 13.9 (1.3) Watts (30 km cycling) - - 223.0 (11.9) RE (slope) .232 (.013) - .213 (.027) * Denotes statistical significance between T1 and T3 (p < 0.05). # Denotes difference between T1 and T2 (p < 0.01). ventilatory equivalent for oxygen (VE/VO 2) without an accompanying increase in the ventilatory equivalent for carbon dioxide (VE/VCO 2) (Davis et al., 1980). Three minutes post exercise, a finger-prick was used to deter- mine blood lactate levels using the Lactate Plus lactate analyzer (Sports Resource Group, Hawthorne, NY). Heart rate was measured continuously throughout the trial and Borg’s Ratings of Perceived Exertion (RPE) was used to subjectively measure exertion (Borg, 1998) at the end of each stage. Prescribing and monitoring intensity during the 10 km run and 30 km cycling bout Based on individual ventilatory threshold values, initial exercise intensity (running speed and wattage, respective- ly) for the 10 km run and 30 km cycling bout was set at 98% of VT for each subject. By definition, VT represents a workload that subjects can maintain for long durations. If a subject struggled to complete either of the steady state bouts during Trial-2 or Trial-3 at an intensity
initial exercise intensity (running speed and wattage, respective- ly) for the 10 km run and 30 km cycling bout was set at 98% of VT for each subject. By definition, VT represents a workload that subjects can maintain for long durations. If a subject struggled to complete either of the steady state bouts during Trial-2 or Trial-3 at an intensity equal to 98% of VT, the intensity was decreased by 5%. To assure that individuals were not working above the desired inten- sity, oxygen uptake was monitored at regular intervals throughout the 10 km run [km 0-2, 5-7, and 9- 10] and 30 km cycling [km 0- 3, 10- 13, and 25- 28] bout. Subjects provided ratings of perceived exertion (RPE) every 5 minutes, while heart rate was monitored continuously throughout each of the three trials. Each subject was re- quired to have an organized dietary and hydration plan, designed to mimic individual race-day nutritional prefer- ences. Calculation of running economy Various methods are available for the calculation of run- ning economy (RE). For the purposes of this study, RE was calculated as the oxygen uptake per given running speed (Conley and Krahenbuhl, 1980; Costill and Fox, 1969; Morgan and Craib, 1992). The slopes of the linear regressions obtained from submaximal VO 2 during Trial- 1 and Trial-3 were subsequently compared (Costill and Fox, 1969; Saunders et al, 2004). Running economy was calculated for all sub-threshold running speeds and one running speed above the mean calculated threshold. Statistical analyses All data shown are mean ± standard deviation. All statis- tical procedures were performed using R statistical pro- gramming language. Normality was determined prior to analysis. Univariate repeated-measures analysis of vari- ance (ANOVA) was used to determine differences b e- tween measures of VO 2max, HRmax, BLmax, RPEmax, VT (ml∙kg -1 ∙min -1 ), VT (% VO2max), HR at VT, and RPE at VT across the three trials. Similarly, a repeated measures ANOVA assessed differences in oxygen uptake at each running speed between Trial-1 and Trial-3. Greenhouse- Geisser corrections addressed any sphericity violations and Bonferroni post-hoc tests compared differences whenever a
measures of VO 2max, HRmax, BLmax, RPEmax, VT (ml∙kg -1 ∙min -1 ), VT (% VO2max), HR at VT, and RPE at VT across the three trials. Similarly, a repeated measures ANOVA assessed differences in oxygen uptake at each running speed between Trial-1 and Trial-3. Greenhouse- Geisser corrections addressed any sphericity violations and Bonferroni post-hoc tests compared differences whenever a main effect was present. Paired t-tests deter- mined significant differences between maximal running speed, running speed at VT, and the regression slopes of VO 2 per running speed between Trial-1 and Trial-3. Sig- nificance was set at α = 0.05 for all statistical procedures. Results Mean resting heart rate was 55(±8) bpm and was similar for all 3 trials. In addition, no significant differences in any of the potential confounding variables [hydration status, reported sleep, fatigue, and muscles soreness] were observed among the three trials (data not shown). Maximal and submaximal values attained during the three trials appear in Table 1. There were no signifi- cant differences in VO 2max values attained during the three trials (F (2,12) = 3.02, p = 0.087, η 2 = 0.335). Differences in maximal HR trended toward significance (F (2,12) = 3.73, p = 0.055, η 2 = 0.656), and visual inspection suggests lower HR max in Trial- 3 compared to Trial-1 and Trial-2. A main effect for trial was observed for BL max (F(2,12) = 28.9, p < 0.001, η 2 = 0.828). Bonferroni post-hoc tests indicate a significant difference between BL max values obtained during Trial-1 and Trial-3 (p = 0.006). No differences were observed in RPE max among the three trials (F(2,12) = 0.93, p = 0.42, η 2 = 0.135). Differences in maximal run- ning speeds between Trial-1 and Trial-3 approached sig- nificance (df = 6, t = 2.291, p = 0.06). No differences were observed in VT among the three trials; sphericity
Effect of a duathlon simulation on VT and RE 250 was violated (p < 0.001) and a Greenhouse-Geisser cor- rection was applied (Ɛ = 0.503, p = 0.34, η 2 = 0.153). No differences among the three trials were observed for HR at VT (F (2,12) = 1.71, p = 0.22, η 2 = 0.222), or for RPE at VT (F (2,12) = 3.21, p = 0.08, η 2 = 0.348). No differences were observed between running speeds at VT between Trial-1 and Trial-3 (df = 6, t = 1.333, p = 0.23). Comparison of RE expressed as relative oxygen uptake at each running speed indicated a significant inter- action (F (6, 36) = 4.88, p = 0.001, η 2 = 0.449) between time (Trial-1 and Trial-3) and running speed (Figure 2), ho w- ever, the simple comparisons only approached signifi- cance (9.6 km∙h -1 , p = 0.09; 11.2 km ∙h -1 , p = 0.06; 12.8 km∙h -1 , p = 0.08). The slope of the regression lines for Trial-1 and Trial-3 were not statistically different (Table 1), and were very similar to those values previously re- ported (Conley and Krahenbuhl, 1980; Costill and Fox, 1969). No differences were observed between the regre s- sion slopes of submaximal VO 2 between Trial-1 and Tri- al-3 (df = 6, t = 1.658, p = 0.15). Discussion The purpose of this study was to investigate the effects of a laboratory based duathlon simulation, completed at the highest attainable intensity, on final run performance. Our goal was to effectively control for exercise intensity with- in a thermoneutral environment and examine the physio- logical responses of highly-trained multisport athletes. We hypothesized that; 1) VO 2peak would not differ be- tween Trial-1 and Trial-3, 2) VT would decrease during the final running bout of the duathlon simulation, and 3) RE would decrease during Trial-3. We observed a signifi- cant decrease in relative oxygen uptake at VT during Trial-3 compared to Trial-1. Corresponding running speeds decreased; falling from 15.5 km∙h -1 during Trial-1 to 13.9 km∙h -1 during Trial-3. In our population, this de-
Trial-3, 2) VT would decrease during the final running bout of the duathlon simulation, and 3) RE would decrease during Trial-3. We observed a signifi- cant decrease in relative oxygen uptake at VT during Trial-3 compared to Trial-1. Corresponding running speeds decreased; falling from 15.5 km∙h -1 during Trial-1 to 13.9 km∙h -1 during Trial-3. In our population, this de- cline in running speed equates to a 134 second increase in the time to complete a 5 km running bout, a substantial difference for any competitive athlete. Training practices that mitigate this decline in running speed would provide significant competitive advantages to high performance multi-sport athletes. Contrary to the findings previously reported by Vallier et al. (2003), these results suggest a negative ef- fect of the cycle- to-run transition during a duration event and more closely agree with findings previously reported in triathlon (De Vito et al., 1995) . However, it is im- portant to consider the external validity of Vallier et al. (2003). The complex nature of an ITU Duathlon often means that athletes are not always working at, or near, threshold. The draft legal nature of the ITU Duathlon means that race dynamics are drastically different from the highly controlled laboratory environment of the cur- rent study. Both tactical awareness and split second deci- sion-making are vitally important in determining who crosses the line in first place. For instance, drafting during a cycling event has been shown to elicit a 39% reduction in energy cost (McCole et al., 1990) . The nature of these events forces these athletes to periodically work above threshold in an effort to either strain, or detach, their op- ponents from the lead group, or maintain contact with others trying to form a split in the group. While an out- door simulation may offer a more race- like experience by allowing individuals to employ pacing strategies similar to a competitive event, our design maintains a higher degree of control. This provides us the opportunity to determine the physiological consequences associated with having performed a duathlon event at the highest attaina- ble intensity. While it
Description
The study investigates the impact of duathlon simulation on athletic performance metrics.