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Race Performance and Exercise Intensity of Male Amateur Mountain Runners During a Multistage Mountain Marathon Competition Are Not Dependent on Muscle Strength Loss or Cardiorespiratory Fitness

Gatterer, Hannes; Schenk, Kai; Wille, Maria; Raschner, Christian; Faulhaber, Martin; Ferrari, Marcello; Burtscher, Martin

Journal of Strength and Conditioning Research: August 2013 - Volume 27 - Issue 8 - p 2149–2156
doi: 10.1519/JSC.0b013e318279f817
Original Research
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Gatterer, H, Schenk, K, Wille, M, Raschner, C, Faulhaber, M, Ferrari, M, and Burtscher, M. Race performance and exercise intensity of male amateur mountain runners during a multistage mountain marathon competition are not dependent on muscle strength loss or cardiorespiratory fitness. J Strength Cond Res 27(8): 2149–2156, 2013—The aims of this study were to quantify the cardiorespiratory fitness level of amateur mountain runners and to characterize the related cardiorespiratory and muscular strain during a multistage competition. Therefore, 16 male amateur participants performed an incremental treadmill test before the Transalpine-Run 2010. Besides race time, heart rate (HR) was monitored using portable HR monitors during all stages, and countermovement jump ability was assessed after each stage. Overall race time and race times of the single stages were not related to any of the cardiorespiratory fitness parameters assessed during the incremental treadmill test (e.g., V[Combining Dot Above]O2max, ventilatory threshold). Average HR during the first stage was 81 ± 7% of the maximal HR and decreased to 73 ± 6% during the following stages. Creatine kinase activity as an indirect marker of muscle damage and strain amounted to 1,100 ± 619 U·L−1 after the third stage and was related to the decrease in the mean HR between stage 1 and stage 2 (r = −0.616, p < 0.05). Jump ability decreased continuously in the course of the race but was not related to exercise intensity. In conclusion, this study showed that race performance during a multistage mountain marathon does not depend on cardiorespiratory fitness parameters determined in the laboratory. Furthermore, the mean HR decreased after the first stage and remained constant during the following stages independent of the decreased muscle strength. We interpret these data to mean that performance differences were a result of insufficient recovery after the first day of multistage mountain running and the different individual pacing strategies. It is worth mentioning that also other factors, not determined in this investigation, could be responsible for the present outcomes (e.g., nutrition, genetics, psychological and environmental factors, or different training programs).

1Department of Sport Science, University of Innsbruck, Innsbruck, Austria

2School of Sports Medicine, University of Verona, Verona, Italy

Address correspondence to Hannes Gatterer, hannes.gatterer@uibk.ac.at.

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Introduction

Athletes are continuously in search of new challenges exploring the limits of their individual physical and mental performance capacity. Although most contemplate finishing a marathon run once in their life, others are challenged when the race route crosses deserts, overcomes several thousand meters of difference in altitude, or strings together multiple marathon stages. With a total distance of 305 km within 8 days and 13,500 m of ascent, the Transalpine-Run is in line with the trend of extreme sporting challenges.

Successful performance in such events relies on several factors, of which willingness to endure pain and mental toughness are indispensable prerequisites (7). Also, an outstanding cardiorespiratory fitness, extraordinary muscular endurance and exercise economy (4), intelligence and experience concerning effort regulation (9), adequate nutrition (8,18), and training strategies (17) are important factors for high performance and for safety and injury prevention (7). Despite increasing popularity of multistage mountain/track running and booming numbers of races worldwide, scientific interest in this discipline is still poor. Most research has considered single-stage mountain running competitions or has focused on injuries, health problems, hydration status, or anthropometry (3,4,6,8,17,18,23,24,26). To our knowledge, no study has examined the heart rate (HR) response, indicative of exercise intensity (1,11), and the loss of jump ability, indicative of muscle strength loss (5,6,22), during a multistage mountain running race or the cardiorespiratory fitness of amateur competitors. Despite the multifactorial nature of performance in multistage mountain running, this information could be essential to evaluate the cardiorespiratory and skeletal muscular strain and to estimate the metabolic demand for the participants. On the basis of these data, possible health risks could be appraised, appropriate training strategies developed, and proper advice for nutritional intake derived. Therefore, the goals of this study were (a) to describe the HR response and to evaluate lower-body muscle strength in the course of the Transalpine-Run 2010 and (b) to determine the cardiorespiratory fitness parameters (e.g., V[Combining Dot Above]O2max, ventilatory threshold [VT]) of the participants. We hypothesized that cardiorespiratory fitness parameters at least partly determine running performance during multistage mountain running, as was shown for single-stage mountain races (4), and that the frequent uphill (concentric exercise), and especially downhill (eccentric exercise), running over the stages may lead to a loss of muscle strength (10,21) with a concomitant reduction in power output and related HR response.

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Methods

Experimental Approach to the Problem

The GORE-TEX Transalpine-Run 2010 was held from September 4 to 11, 2010. Two months before the start of the race, all teams—each team consisted of 2 persons—that registered for the competition were invited by the organizers of the race to participate in the study. The first 15 teams that volunteered to participate were included in the study. In the course of the Transalpine-Run, participants had to complete 8 stages in 8 consecutive days, with a total distance of 305 km and a total gain of altitude of 13,500 m. Figure 1 gives an outline of the course including the horizontal distance (kilometers) and the high meters (meters) for all stages.

Figure 1

Figure 1

Within 2 weeks before the competition, all study participants performed a laboratory incremental exercise test to exhaustion to determine maximal HR (HRmax) and V[Combining Dot Above]O2max and to identify different intensity zones (see following). During all stages of the competition, HR response was measured in all study participants, and the intensity zones determined in the laboratory test were used to evaluate exercise intensity. After finishing each stage, the participants performed 3 countermovement jumps (CMJs) for investigating the possible changes in muscle strength during the competition week.

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Subjects

A total of 15 teams (N = 30, 24 men and 6 women) volunteered to participate in the study. For the final statistical analysis, 16 men were included. The reasons for the large drop out were as follows: 1 participant was unable to perform the first measurement session. During the competition, 3 women and 2 men abandoned the race because of medical problems, and 1 woman and 1 man quit because of the retirement of the partner. As only 2 women finished the challenge, female participants were excluded from the analysis. During the competition, some degree of failure of the HR monitors was documented. Seven participants had missing values during only 1 stage (1 during stages 1, 3, 4, and 6 and 3 during stage 8), so the missing values were replaced with the mean of the group for the specific stage. Subjects were excluded from analysis if HR values were not available for ≥2 stages (n = 3). Table 1 shows the baseline characteristics of the 16 amateur participants included in the analysis. All participants were informed of the experimental procedures and provided written informed consent. The study was approved by the Institutional Review Board of the Department of Sport Science of the University of Innsbruck.

Table 1

Table 1

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Procedures

Laboratory Exercise Test

A maximal treadmill (Pulsar; HP-Cosmos, Traunstein, Germany) test was performed applying a modified Bruce protocol, with each step lasting 2 minutes (14). During the test, HR was registered. Gas exchange variables, including the rate of ventilation (VE), V[Combining Dot Above]O2, V[Combining Dot Above]CO2, and end-tidal partial pressure of oxygen (PETO2) and carbon dioxide (PETCO2) were recorded breath by breath (Oxycon Mobile; CareFusion, Hoechberg, Germany). A test was considered maximal when 3 of the following criteria were fulfilled: V[Combining Dot Above]O2 plateau at peak exercise, respiratory exchange ratio (V[Combining Dot Above]CO2/V[Combining Dot Above]O2) >1.10, peak HR reaching at least 90% of the theoretical maximal HR predicted for age and gender, an indication of maximal exhaustion by the athlete (12). The VT was defined as the point of a nonlinear increase in VE in combination with an increasing equivalent for oxygen (VE/V[Combining Dot Above]O2) and end-tidal O2 (PETO2) without a concomitant increase in the ventilatory equivalent of CO2 (VE/V[Combining Dot Above]CO2). The respiratory compensation point (RCP) was determined by an increase in both VE/V[Combining Dot Above]O2 and VE/V[Combining Dot Above]CO2 and a concomitant decrease in end-tidal CO2 (PETCO2) (27). Ventilatory thresholds were visually determined by 2 experienced investigators, and consensus-based values were used for further analysis. Four exercise intensity zones were defined as follows: the low-intensity zone was characterized by an HR below VT. The HR range between VT and RCP was split in 2 intensity zones to distinguish the exercise strain better: the moderate-intensity zone was defined by an HR between VT and [(HRRCP – HRVT)/2 + HRVT], the high-intensity zone ranged between the latter and RCP, whereas an HR above RCP marked the very high-intensity zone (25).

No intense training was performed during the day before the test. Days before testing, the participants were advised to follow their normal precompetition preparation habits with focus on proper drinking, eating, and sleep. All participants were amateurs, and they presented to the laboratory when they had free time. Therefore, time of testing was different for all participants. The ambient temperature during the test was kept constant between 20 and 22° C.

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Measurements During the Competitions

In the afternoon before the race start (September 4), a trial measure session was carried out to discuss the last open questions and to familiarize the participants with the HR monitor. Heart rate analyzers from 2 different companies were used: Polar RS800CX (Polar, Kempele, Finland) and Garmin Forerunner 405 (Garmin, Olathe, KS, USA). These types of HR analyzers were shown to be valid and reliable when tested against an electrocardiogram (1). After every stage, the HR files were saved by the study coordinators.

Official race times of the participants were obtained from the race office. V[Combining Dot Above]O2 during the stages was derived from the race time of the stages using a modified formula of the American College of Sports Medicine for treadmill running, that is, V[Combining Dot Above]O2 = 1.1 [0.2 speed (m·min−1) + (0.9 speed (m·min−1) × fractional grade)] + 3.5 (2,4).

The CMJs were performed on a portable force platform (MLD-Station Evo2; SP Sportdiagnosegerate GmbH, Innsbruck, Austria) within 1 hour after finishing each stage. The CMJs on the MLD force plates have been shown to be a suitable test to determine muscle strength in athletes (22). The force platforms (2 separate force platforms) contain 4 one-dimensional force transducers, each able to measure a maximum-functional force of 7.5 kN with a sampling rate of 1,000 Hz. The measurement precision is 0.1% of the end result. The software (MLD 2.0) uses the ground reaction force record obtained from the force platforms to calculate parameters as described by Linthorne (19). The CMJ was performed 2-footed, with participants instructed to place their hands on their hips to eliminate the influence of the arm-swing impulse. The jump was started from an erect position. When given a verbal command, the athlete made the downward countermovement to his preferred position and then immediately jumped vertically for maximum height. Three maximal CMJs were recorded, and the trial with the best jump height was used for further analysis.

Creatine kinase (CK Boehringer, Ingelheim am Rhein, Germany) levels were measured from capillary blood samples after stage 3 (Reflotron Sprint; Mannheim, Germany; reference range for men: 24–195 U·L−1 at a measurement temperature of 37 °C). When the CK activity was out of the range of the device, the maximal measured activity (i.e., 1880 U·L−1) was registered (n = 4) because dilution was not possible in the field setting.

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Statistical Analyses

Data were analyzed using PASW Statistics 18 (SPSS, Hong Kong). Repeated measures analysis of variance (ANOVA) was used to investigate the changes in average HR and in partial race times spent in each of the 4 intensity zones in the course of the 8 stages. When significant changes were identified, Bonferroni post hoc analysis was performed. Cohen effect size (ES) was calculated for significant ANOVA outcomes. Pearson or Spearman correlation analysis was applied as appropriate to identify the relationships among cardiorespiratory fitness parameters, race time, and CK values. Mean ± SD and confidence intervals, when appropriate, were used to describe variables. A p value of ≤0.05 was used as a 2-tailed level of significance.

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Results

The results of the maximal incremental treadmill test are shown in Table 1. Table 2 shows the mean race time for every stage, considering all 16 participants. The overall race time (hours:minutes) for the participants was 49:37 ± 7:47 (range: 37:06–62:36). The winning times in the different age categories, men, master (age of both team partners >80 years), and senior master (age of both team partners >100 years), were 28:29, 31:17, and 36:37, respectively. The slowest times were 80:12, 62:36, and 58:42, respectively. No correlation was found between race times (overall and single stages) and cardiorespiratory fitness parameters of the participants (e.g., V[Combining Dot Above]O2max, VT, RCP). Figure 2 shows an exemplary HR response during the stages in view of the altitude profile of the route. Mean HR of all participants was significantly reduced in the course of the race (ANOVA, p < 0.001, ES = 0.930). The post hoc tests revealed a significant reduction of the mean HR in all stages when compared with stage 1 (p < 0.05; Table 2). Distribution of the exercise intensities (given as a percentage of the race time) during the 8 stages is shown in Figure 3. There were significant changes over time for the low-intensity zone (ANOVA, p < 0.001, ES = 0.599). The post hoc tests revealed a significantly higher proportion of the low-intensity zone in stages 2, 4, 5, 6, and 7 when compared with stage 1 (p < 0.05). Further significant changes were found over time when the high-intensity and the very high-intensity zones were combined (ANOVA, p < 0.001, ES = 0.919). The post hoc tests revealed a significantly higher proportion of the combined zones in all stages when compared with stage 1 (p < 0.05). The calculated mean V[Combining Dot Above]O2 during the first stage was 36 ± 5 ml·min−1·kg−1, corresponding to 65% of the V[Combining Dot Above]O2max determined in the laboratory. During the remaining stages, the mean V[Combining Dot Above]O2 was ∼32 ± 5 ml·min−1·kg−1, corresponding to 57% of the V[Combining Dot Above]O2max, with one exception during stage 5 where the V[Combining Dot Above]O2 was 25 ± 4 ml·min−1·kg−1. Jump ability decreased in the course of the race (ANOVA, p < 0.05, ES = 0.571; Table 2). The CK activity amounted to 1,100 ± 619 U·L−1 after stage 3 and was related to the decrease in the mean HR from stage 1 to stage 2 (r = −0.616, p < 0.05).

Table 2

Table 2

Figure 2

Figure 2

Figure 3

Figure 3

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Discussion

The main findings of this study are (a) that the mean HR during a 8-day mountain marathon competition decreased after the first stage but was stable at ∼70% of the maximal HR during the later stages independent of the decreased muscle strength and (b) that the cardiorespiratory fitness parameters of the amateur participants did not predict performance during the race. At present, the only study that has investigated the HR response in a multistage mountain race competition (Bike Transalp) comparable with the present race was performed among mountain bikers (28). Wirnitzer and Kornexl (28) found average HRs of ∼80% of the maximum throughout the 8 stages. In contrast, for mountain runners, we found that after the first stage, with an exercise intensity of ∼80% of the maximal HR, running intensity decreased to ∼70% for the remaining 7 stages. The reduction of high-intensity running phases already after the first day may be linked to the movement pattern of mountain running. Typically for such races, uphill running (i.e., concentric exercise) alternates with downhill running (i.e., eccentric exercise). The eccentric exercise was shown to initiate inflammation and to induce muscle damage (16), with symptoms of muscle soreness and decreased muscular strength that can be seen for some days after the damaging exercise (10,21). Although most participants specifically trained for the Transalpine-Run challenge, 25% reported signs of muscle pain after the first stage (data not systematically determined). In agreement to this, we found high CK activities (1,100 ± 619 U·L−1), indicative of muscle damage and strain (5). Therefore, the relationship between CK activity and the decrease in the mean HR from stage 1 to stage 2 could mean that because of muscle strain and pain, exercise intensity was lowered and, as a consequence, also mean HR.

Furthermore, we hypothesized that the decreased jump ability, indicative of loss of muscle strength (5,6,22), may influence performance throughout the competition week. Interestingly, this was not the case because mean HR was found to be constant over stages 2–8. In fact, when regeneration is incomplete, performance plateaus (15). The present results suggest that during mountain running, an exercise intensity of ∼70% of the maximum HR can be kept despite a substantial strength loss of the working muscle.

Several other factors might also have influenced running speed and daily performance during the competition week. As mentioned earlier, only teams consisting of 2 persons were allowed to participate in the race. So when one could not hold the pace, the other had to slow down too. Furthermore, for most of our participants, this was the first experience in a multistage mountain marathon race, and their main goal was to stay the course. As a consequence, they might have consciously slowed down after the first stage because they did not know how to ration their forces to reach the final arrival. Additionally, it has to be recognized that successful performance in such ultraendurance events relies on psychological and personality characteristics of the participants, for example, willingness to endure pain or mental toughness, or both.

All these factors might explain why no correlations between the cardiorespiratory fitness parameters and the race time were found. It seems as if exercise intensity during a multistage mountain marathon race is regulated rather by self-assessment, prior experience, and sensation of and coping with pain than by physical fitness, at least in this group of amateur participants. Of course, a certain degree of physical fitness is prerequisite to finish the competition. The average V[Combining Dot Above]O2max found in the present investigation was 56 ± 5 ml·min−1·kg−1, the highest value was 66 ml·min−1·kg−1, and the lowest was found for a 46-year-old man with a value of 47 ml·min−1·kg−1. This value, however, is still 15% higher when compared with the 50th percentile of the sedentary peers, and the mean of the present group is even higher by 36% (2).

Some issues should be kept in mind when interpreting the present results. It has to be mentioned that maximum HR was measured only at the beginning of the competition. When considering that during stage races, a progressive decrease in maximum HR may occur (13,20); the physiological strain over the competition days may be higher despite a comparable mean HR response. Measurements of HR during mountain races may also be influenced by different conditions, for example, high-altitude environment, hydration status, and cardiovascular drift (1). This could lead to a mild overestimation of the exercise intensity when based on HR monitoring and analysis (25). Nevertheless, in the field setting, HR monitoring is the most commonly used method to get an indication of the exercise intensity (1,11). In this regard, the apparent dissociation of the V[Combining Dot Above]O2-HR relationship (reduced V[Combining Dot Above]O2 despite an unchanged HR response) in the course of stage 5 needs to be addressed. A possible explanation might be the comparably higher mean altitude reached during this stage when compared with the other stages (Figure 2).

Besides these issues, a further limitation was that because of the field setting (inadequate measurement places), CK values were only available after stage 3. Additionally, the approach to replace the 4 missing CK values with the highest detected value could have biased the presented outcomes because during such an event very high values are possible. Furthermore, muscle soreness was not systematically determined.

In conclusion, this study showed that exercise intensity—evaluated by HR monitoring—during an 8-stage mountain marathon competition was reduced already after the first stage. The exact cause for this reduction could not be evaluated, but muscle strain and soreness (indicated by the high CK activity), individual pacing strategies, and psychological factors might be involved. Present results further suggest that during multistage mountain running, an exercise intensity of ∼70% of the maximal HR could be kept even though muscle strength decreases. Interestingly, cardiorespiratory fitness parameters determined in the laboratory did not predict race performance during a multistage mountain marathon competition, suggesting that other factors may substantially influence race performance, for example, willingness to endure pain, mental toughness, prior experience, or pacing strategy, or all.

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Practical Applications

Altogether, the present results suggest that participants of a multistage mountain running competition need a good but not an extraordinary cardiorespiratory fitness (i.e., V[Combining Dot Above]O2max) (2). Furthermore, data imply that the running intensity should not exceed 70% of the maximal HR determined in the laboratory when the goal is to successfully complete the race. Besides this, the capacity to recover quickly, to effectively restore glycogen stores and rehydrate, to ignore increasing physical soreness and decreasing mental motivation, empathy for the partner and extraordinary resilience are indispensable attributes of athletes participating in the Transalpine-Run. From a practical point of view in the preparation phase for such an event, focus should be given on specific training interventions including multiday training cycles, uphill and downhill running, and good mental preparation. During the race, optimizing pacing and recovery strategies might help to improve race performance and likely also reduce the risk for adverse events.

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Acknowledgments

We are indebted to all the participants of our study, in particular for their willingness to submit themselves to repeated measurements. We thank the organizer (Plan B) for their support. The study was funded by the “Aktion D. Swarovski & Co. 2010.” We disclose professional relationships with companies or manufacturers who benefit from the results of the present study. The use of products does not in any way constitute endorsement or recommendation of the products.

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Keywords:

energy expenditure; mountain running; heart rate response

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