Comparison of Exclusive Double Poling to Classic Techniques of Cross-country Skiing

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY-NC-ND 4.0 https://creativecommons.org/licenses/by-nc-nd/4.0/ Comparison of Exclusive Double Poling to Classic Techniques of Cross-country Skiing 2018 The Author(s). Published version Stöggl, Thomas; Ohtonen, Olli; Takeda, Masaki; Miyamoto, Naoto; Snyder, Cory; Lemmettylä, Teemu; Linnamo, Vesa; Lindinger, Stefan Josef Stöggl, T., Ohtonen, O., Takeda, M., Miyamoto, N., Snyder, C., Lemmettylä, T., Linnamo, V., & Lindinger, S. J. (2019). Comparison of Exclusive Double Poling to Classic Techniques of Crosscountry Skiing. Medicine and Science in Sports and Exercise, 51(4), 760-772. https://doi.org/10.1249/MSS.0000000000001840 2019 Comparison of Exclusive Double Poling to Classic Techniques of Cross-country Skiing THOMAS STO ¨GGL 1 , OLLI OHTONEN 2 , MASAKI TAKEDA 3 , NAOTO MIYAMOTO 4 , CORY SNYDER 1 , TEEMU LEMMETTYLA ¨ 2 , VESA LINNAMO 2 , and STEFAN JOSEF LINDINGER 1,5 1 Department of Sport and Exercise Science, University of Salzburg, Hallein/Rif, AUSTRIA; 2 Faculty of Sport and Health Sciences, Sports Technology, University of Jyva¨skyla¨, Vuokatti, FINLAND; 3 Faculty of Health and Sports Science, Doshisha University, Tatara, Kyotanabe, Kyoto, JAPAN; 4 New Industry Creation Hatchery Center, Tohoku University, Aramaki, Aoba, Sendai, Miyagi, JAPAN; and 5 Center of Health and Performance at the Department of Food and Nutrition and Sport Science, University of Gothenburg, Gothenburg, SWEDEN ABSTRACT STO ¨GGL, T., O. OHTONEN, M. TAKEDA, N. MIYAMOTO, C. SNYDER, T. LEMMETTYLA ¨, V. LINNAMO, and S. J. LINDINGER. Comparison of Exclusive Double Poling to Classic Techniques of Cross-country Skiing. Med. Sci. Sports Exerc., Vol. 51, No. 4, pp. 760–772, 2019. Introduction: This study aimed to 1) determine basic physiological demands during a simulated on-snow cross-country skiing (XCS) race when using grip-waxed skis (all classic XCS techniques [CLASSIC]), versus glide-waxed skis for exclusive double poling (DP) and 2) analyze in which track sections DP is different from CLASSIC under controlled gliding conditions in elite junior and senior skiers. Methods: Nineteen male and female elite XC skiers performed 1) two randomized simulated XCS races over 5.3 km using DP or CLASSIC measuring section times, V ˙O 2 , HR, blood lactate, and RPE; and 2) V ˙O 2peak tests using diagonal stride and DP on treadmill. Results: The total group showed no differences in performance or physiological responses between DP and CLASSIC. Elite male skiers achieved improved (~23 s, PG0.05), male juniors equal (P90.05) and females worse (~43 s, PG0.05) performance with DP versus CLASSIC. Flat and undulating terrain favored DP in men, whereas uphill favored CLASSIC in females (~60 s). Uphill sections showed the greatest group differences. Greater RPE was found in the arms during DP, whereas RPE was greater in the legs using CLASSIC. V ˙O 2peak in DP was ~95% of V ˙O 2max .Conclusions: Male skiers demonstrated superior performance with exclusively using DP on a Fe ´de ´ration International de Ski regulation-compliant XCS track, whereas junior males achieved similar, and females’ weaker performance using DP versus CLASSIC. The greatest potential in females is in uphill sections where they distinctly lose time. Exclusive DP might only be beneficial in athletes with high upper-body capacity, and double-pole–specific training and technique. To generalize the findings of the current study, further analysis of snow conditions and course topography is required. Key Words: BLOOD LACTATE, GRIP-WAX, HEART RATE, OXYGEN UPTAKE, PHYSIOLOGICAL RESPONSE, RPE, SIMULATED RACE Recently, the double poling (DP) technique has rapidly developed as one of the more used of the four main techniques (DP, DP with kick [DPK], diagonal stride [DIA], and herringbone) during classic cross-country skiing (XCS). In the last decade, a new sprint DP technique was proposed (1), which has recently been developed further (2–5). To date, several elite skiers exclusively execute the DP technique successfully throughout an entire race instead of using grip-wax, which allows utilization of all classic XCS techniques, such as DIA or DPK (1–3,6–8). In the long-distance Ski-Classics series, currently almost all races, (except the 50-km‘‘ReistadlLpet,’’ which has two long uphill sections of more than 300 vertical meters), are won by exclusively using the DP technique. Even in World Cup distance racing, certain skiers have begun to successfully use exclusively DP (two podiums and two victories; unpublished data based on personal video analysis). By using skis without kick-wax during DP, the gliding properties of the ski may be enhanced. Combined with improvements in upper-body capacity and improved technique, certain athletes may be more economical and efficient on certain sections of the course. In an attempt to counteract this development, the Fe ´de ´ration International de Ski (F.I.S.) recently introduced two new rules to limit the exclusive use of DP: First, maximum pole Address for correspondence: Thomas Sto¨ggl, Department of Sport and Exercise Science Schlossallee 49, 5400 Hallein/Rif, Austria; E-mail: thomas.stoeg[email protected]. Submitted for publication April 2018. Accepted for publication October 2018. 0195-9131/19/5104-0760/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE Ò Copyright Ó2018 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine. This is an openaccess article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. DOI: 10.1249/MSS.0000000000001840 760 APPLIED SCIENCES length is limited to 83% of the athletes height, and second, introducing no-DP zones where exclusive DP is prohibited. One question arises: Can this development in favor of the DP technique be explained based on scientific state of the art knowledge? Hoffman and Clifford (9) demonstrated the best economy on flat terrain and moderate speeds (14.2 kmIh j1 ) using DP, whereas DIA elicited the greatest physiological demand and highest perceived effort among all analyzed classic and skating XCS techniques. The improved economy using the DP technique was attributed to more effective storage and recovery of elastic energy, a greater proportion of forces produced in line with the direction of travel, and a lower air resistance due to a partially tucked position. At that time, it was suggested that the greater economy of DP may be advantageous in certain race conditions if the upper body is adequately prepared (10). In this context, Sto¨ggl and Holmberg (2) recently demonstrated that changes that have occurred in the DP technique enable this technique to be used more extensively on a variety of inclines. On flat terrain, the very short ground contact time has been suggested to be the main limitation, whereas on steep uphill terrain, the considerable reduction in swing time and high pole forces challenge the athlete. By adapting a special uphill DP technique (e.g., ‘‘pumping DP’’), more rapid repositioning of the body is guaranteed and enhances uphill DP performance. However, it was also speculated that extended use of the DP technique might be limited by its greater anaerobic demands (11). More than 20 yr later, Pellegrini and co-workers (12) demonstrated that, in national level XC skiers roller skiing on a treadmill, DP is the preferred technique at low inclines (upto2-C). At moderate inclines (2-C–3-C), their skiers switched to DPK and all used DIA on inclines greater than 6-C. In that investigation, no skier used DP on an incline steeper than 4-C. Furthermore, when focusing on the sprint start, it was demonstrated that using DIA was faster over the first 38 m when compared with exclusive DP (13). These later findings would not support the current trend for exclusive execution of DP during XCS racing. Although research on the DP technique has been extensive during the past 13 yr, both with elite skiers in the laboratory roller skiing on a treadmill (1–3,14,15) and with regional-to-national level skiers (12), to date, no reports on elite athletes during competition on snow have appeared. Therefore, the physiological mechanisms and performance differences behind the exclusive DP versus all classic XCS techniques (adapted to track topography) are not yet established in a valid environment. Furthermore, the effects of biological sex or maturity level (e.g., elite juniors vs elite seniors) were not within the scope of laboratory or field trials with respect to this research question. The aims of the current study were: 1) determine the basic physiological demands during a simulated on-snow XCS race when using grip-waxed skis and all classic XCS techniques (CLASSIC) versus only glide-waxed skis and exclusive DP with female and male world-class athletes and junior skiers under controlled gliding conditions; 2) analyze in which sections of a track exclusive DP might lead to gained or lost time compared with CLASSIC, considering both the aspect of performance level as well as sex. The hypotheses were that 1) based on their higher DP capacity, senior male XC skiers would demonstrate improved performance using the DP technique when compared to CLASSIC, while in female and or junior skiers it would be the opposite; 2) exclusive DP would be especially superior in flat and slightly uphill sections of a track, whereas DIA would be in favor on steeper uphills (i.e., 94-C). METHODS Participants. Nineteen elite female and male XCS athletes (current members of the Finnish National Team or Junior Team) volunteered to take part in this study (mean T SD: age, 24 T7 yr; body mass, 71 T9 kg; height, 178 T6cm). All participants were well-trained professional and semiprofessional athletes (mean V ˙O 2max 71.1 T7.6 mLIkg j1 Imin j1 (range, 60–85 mLIkg j1 Imin j1 )], routinely performing 7 to 10 training sessions each week (mean, 705 hIyr j1 ; range, 550– 770 h), with approximately 110 hIyr j1 [range, 95–130 h] of DP or specific upper-body training). They had been competing in XC skiing competitions for the past 8 to 20 yr and were all healthy during the entire period of testing. Seven of these skiers had earned World Cup points, two of whom were among the top 4 results. For statistical analysis, participants were grouped according to performance level within the male skiers (senior males, international level [n= 5]; junior males, national level [n= 8]), and senior and junior females of national and international level (n= 6). Participants were fully informed about the study details and participation requirements with written and verbal information before providing written informed consent to participate. The study received approval from the local Ethical Committee (EK-GZ: 05/2017) and was conducted in accordance with the Declaration of Helsinki. Overall design. To accommodate the skier_s tight competition schedule, this study was carried out from March 20 to 29, 2017, after the end of the last World Cup and prior to the Finnish national championships. Due to illness, two senior international level elite female skiers who volunteered to take part in the study were not able to attend the measurements (not included above) and thus the females were not grouped as elite and juniors as males were. Each participant was analyzed on two separate days with 1) tests on snow (race simulation) as well as 2) tests in the laboratory on a treadmill using roller skis. On the first day, two separate simulated XCS races (randomized order) on snow over a distance of 5.3 km were performed. This distance of approximately 5 km (shortest distance applied in female skiers distance competitions) was chosen 1) to keep the overall load manageable for skiers performing repeated runs on a race track with a 1-h break in between, 2) to provide a proper study and test economy (logistics), and 3) to be able to get world-class athletes into the study (time budget). One trial DOUBLE POLING THE FUTURE TECHNIQUE? Medicine & Science in Sports & Exercise d 761 APPLIED SCIENCES was performed using grip-waxed skis, enabling leg push-offs and all appropriate classic techniques (CLASSIC) where appropriate, and one trial with only glide-waxed skis (entire ski base), allowing only for DP. In some parts (very steep inclines), the herringbone was allowed in case of lacking upper-body capacity for pure DP (e.g., in case of some of the females). The time engagement of each participant during the on-snow tests (including installation of the equipment at start and removal at the end of the tests) was approximately 2 h. On the second session, laboratory tests with anthropometrical measurements and two V ˙O 2peak roller skiing ramp tests on the treadmill were performed. At least 48 h rest (2–5 d) was given between visits. On both testing days, all participants were asked to report well hydrated and to refrain from consuming alcohol and engaging in strenuous exercise at least 24 h before testing. V ˙O 2peak laboratory tests. The laboratory tests included the determination of body mass, body height, absolute, and relative pole length. Absolute pole length was measured from the tip of the pole to the strap, and relative was defined in terms of percent body height in shoes (F.I.S. international competition rule 343.8.1). Additionally, two incremental roller skiing (roller skis: Marwe 800 XC, wheel N-6, Marwe Oy, Hyvinka¨a¨, Finland) ramp protocols to volitional exhaustion with DIA and DP only (randomized order) were completed to get information about their peak performance and peak physiological output in both skiing techniques. The DP and DIA laboratory performance test protocols were selected based on tests that the athletes were familiar with in performance testing and training settings. To link upperbody capacity to natural skiing performance, the DP protocol was selected as an indicator for upper-body capacity (in contrast to an isolated upper-body exercise as, for example, arm cranking, or seated pull-down exercises) as previous studies have also reported (e.g., (16,17)). Each roller skiing protocol consisted of a 10-min warm-up phase, with 6 min low-intensity (~70% HR max ) and 4 min moderate-intensity (~80% HR max ), after which the ramp protocol in the respective technique began. In between the two ramp protocols, there was a break of 20 min consisting of a 2-min passive rest in which blood lactate was collected 1 min postexercise, followed by a 3-min active cool-down with blood sampling 5 min postexercise and a 15-min passive break before start of the warm-up for the second ramp test. The DIA warm-up protocol consisted of 6 min at 8 kmIh j1 and 3-grade, followed by 4 min at 10 kmIh j1 and 3-grade. The DIA ramp protocol had a fixed treadmill speed of 10 kmIh j1 at a starting grade of 3-which was increased 1-every minute until volitional exhaustion. The cooldown consistedof3minat6kmIh j1 and 3-grade. The DP warm-up protocol consisted of 6 min at 10 kmIh j1 and 2-grade, followed by 4 min at 12 kmIh j1 and 2-grade. The DP ramp protocol had a fixed grade of 2-, a starting speed of 14 kmIh j1 which was increased 1 kmIh j1 Imin j1 until volitional exhaustion. A previous study has shown a close link between flat and uphill DP performance in elite XC skiers, thus, the selection of the 2-inclination for the DP test (2). This inclination also represents a grade familiar to a majority of study participants. Cool-down was the same as that for DIA. For both protocols, peak values for V ˙O 2 , HR, and blood lactate were established. Simulated XCS races. In a counterbalanced X-over design, each of the participants performed one trial with CLASSIC and one trial with exclusive DP with 45-min rest in between. Each trial took place over 5.3 km (two laps of 2.65 km) on a competition track meeting the F.I.S. homologation (course design) regulations. The total climb was 178 m, with a maximal climb of 22 m and a height difference of 23 m. The exact track profile for one lap is illustrated in Figure 1. FIGURE 1—Track profile for one lap of the simulated race. S, section; d, section distance in meter; TC, total climb within section in meter; HD, height difference within section in meter; Var, variable terrain consisting of flat and undulating terrain with moderate inclines with skiers using DP or DPK; Up, uphill section; Down, downhill section. http://www.acsm-msse.org762 Official Journal of the American College of Sports Medicine APPLIED SCIENCES The track was prepared each morning with one classic track all along the track. To prevent shortcutting, the skiing line within the curves was marked. The area for the section times (buried magnets—see further down) was marked with fluorescent spray. Each participant used his/her own poles (similar in the laboratory and outdoor tests and for both conditions), whereas the skis were provided by expert skitechnicians of the Finnish national team. The glide wax was similar for both conditions and across all athletes. The ski base grind and ski stiffness was similar for both conditions within each athlete (ski stiffness was selected relative to the body weight of the skier), and grip wax was selected according to snow conditions. After an individual warm-up of approximately 30 min including the testing of the skis (grip and glide) the participants were instrumented with the measurement equipment (HR belt, V ˙O 2 portable system, and magnetometer attached on the ski). After the V ˙O 2 system was started, the athlete performed a race warm-up for approximately 8 min on the competition track. After a short break (1–2 min), where the timing system (magnetometers) was started, the skier performed the first race simulation using either the CLASSIC or DP condition. Athletes_rate of perceived exertion levels (RPE-BORG scale, 6–20) were taken at the end of the race simulation and the timing system was switched off. Blood lactate was taken from the fingertip in the second and fifth minute post time trial, and the V ˙O 2 system was removed. After a passive break of 5 min, the athlete performed an easy cool-down for 20 min on skis including a ski glide test, followed by a 10-min rest where the V ˙O 2 system was reinstalled. After another 8-min competition warm-up (similar to test trial 1), the second simulated XC skiing race, using the other condition, was performed with maximal effort. The same post time trial procedure as in the first condition was implemented. During each trial V ˙O 2 , HR, blood lactate, section times, whole-body RPE (RPE WHOLE-BODY ), legs only (RPE LEGS ), arms only (RPE ARMS ) and trunk only (RPE TRUNK ) were recorded. Only the mean and peak values across the entire time trial for the collected physiological parameters were entered into the statistical analysis. Furthermore, after each trial, the used skis were tested on an 80-m-long gliding track by the athlete to determine the ski gliding properties for each condition. The ski testing place was wind sheltered and consisted of a gentle downhill that provided a velocity that was comparable to race skiing speeds. Gliding tests were done using the Ski Speed ski timer (Tieto-Oskari Oy, Kajaani, Finland). Each ski was tested five times, the best and worst records were removed. The mean value of the remaining three trials was used for further analysis. External conditions, such as snow and air temperature, humidity, as well as qualitative descriptions of the snow characteristics and atmospheric cloud cover, were measured and documented according to the methods used by the Finnish ski team. Air temperature and humidity were tested using Vaisala HM40 (Vaisala Oy, Vantaa, Finland), snow temperature with Swix digital snow thermometer T0093 (Swix, Lillehammer, Norway), snow humidity using Doser snow moisture meter type 001 (DOSER Messtechnik GmbH & Co KG, Fu ¨ssen, Germany), and the atmospheric cloud cover by visual inspection of an experienced technician with numerical evaluation (0–8). In general, the weather was representative of typical spring conditions in northern Finland. The temperature was below zero during nighttime, but temperature generally rose above 0-C during the daytime. Mean air temperature across the entire testing period was +1.6-CT 1.8-C (range, j2.7-C to +4.2-C) with snow temperatures being fairly consistent and remained under 0-(j1.1-CT 0.9-C; range, j3.4-Ctoj0.6-C). Within each participant, the deviation in air and snow temperature from the start to the end of the on-snow tests was +0.6-CT0.3-Cand+0.2-CT0.3-C, respectively. High air humidity (68% T9%) caused high snow humidity (30% T8% [doser]). Generally, air and snow temperatures were comparable between conditions within athletes. However, snow conditions changed from cold to wet during some trials, and in one case from wet to cold. Depending on the external conditions, the appropriate grip waxes were applied by the expert ski-technician (range in grip wax: Swix VR45 hard wax to Swix KX75 klister). In summary, we tried, as strictly as possible, to control and standardize this outdoor experiment by 1) randomization; 2) glide tests; 3) using the same ski grind, ski stiffness, and glide wax within each athlete; and 4) standardized protocol with respect to break durations, warm-up procedure, cooldown, and passive rest procedure. Instruments. V ˙O 2 was measured using a portable metabolic cart (K5, Cosmed, Italy). Based on the expected high V ˙O 2 in a majority of the elite skiers, the mixing chamber mode with sampling taken every 10 s was applied for both the laboratory and outdoor trials. The athletes were fitted with a proper-size mask covering the mouth and nose (7450 Series V2iMask; Hans Rudolph Inc., Shawnee, KS). Before each test trial, the gas analyzer_s oxygen (O 2 ) and carbon dioxide (CO 2 ) sensors were calibrated using a two calibration procedure with ambient air conditions (20.93% O 2 and 0.03% CO 2 ) and the anticipated expiratory gas percent using calibration gas containing 15% O 2 and 5% CO 2 (UN 1950 Aerosols, Cortex Biophysik GmbH, Leipzig, Germany) (rest volume: nitrogen). The flow volume was calibrated using a 3-L syringe (M9424; Medikro Oy, Kuopio, Finland). Furthermore, a Garmin HR belt was connected via ANT+ to the K5 system. Additionally, an extra HR monitor (Polar V800; Polar electro Oy, Kempele, Finland) with a sampling rate of 1 Hz and an integrated GPS was used. For lactate analysis, a 20-HL capillary blood sample from the fingertip was collected and quantified using an amperometric– enzymatic technique (Biosen S-Line Lab+; EKF-diagnostic GmbH, Magdeburg, Germany). The lactate sensor was calirated before each test using a lactate standard sample of 12 mmolIL j1 . Results within a range of T0.1 mmolIL j1 were accepted. To get exact intermediate times during the race for flat, uphill, downhill sections, undulating terrain, and so on, a DOUBLE POLING THE FUTURE TECHNIQUE? Medicine & Science in Sports & Exercise d 763 APPLIED SCIENCES self-developed measurement system was applied. This system included a magnetometer (Axivity IMU sensor: size, 23 32.5 8.9 mm; weight, 8 g; sampling rate, 50 Hz) that was attached to the tip of the ski. The second component was a custom-made 15-cm-long magnet unit which was a serial arrangement of three sets of double magnets (six magnets of the type: S-20-10-N; Supermagnete, Gottmandingen, Germany) connected using two 50 mm 10 mm iron cylinders. This magnet unit was buried in the snow exactly in the middle between the two single classic tracks (between the two skis) or three in a form of an array of three magnet units crossover the whole track in sections where herringbone technique was expected (i.e., very steep uphills). The accuracy of this system was tested against that of a light-beam system, and the error was found to be within the range of its 50-Hz sampling rate. Sensor data were collected by an in-house smartphone application (SkiSense App, Salzburg Research, Salzburg, Austria) attached to the V ˙O 2 metabolic cart. All data processing was performed using R-Studio (Version 1.1.383) and the Ikemaster software (Ike Software Solutions, Salzburg, Austria). Statistical analysis. All data exhibited a Gaussian distribution verified by the Shapiro–Wilk test and, accordingly, the values are presented as means (TSD). A 2 3 repeated-measures ANOVA (with the two conditions [DP vs CLASSIC] as repeated measures and the three groups [male international level, male juniors national level, females] as independent measures) was performed to test the main effects of the used skiing condition, group, and its interaction. Furthermore, a 2 2 ANOVA with repeated measures (two conditions, two laps) was used to check for differences in pacing between the two laps with respect to the used condition (DP vs CLASSIC). For analysis of differences between the two conditions with each single section, a 9 2 ANOVA with repeated measures was performed for the entire group and for each group separately (nine sections and two laps). In case of significant main effects and/or interaction effects, further post hoc analysis within each group as univariate ANOVA or paired sample ttests were performed. All tests were adjusted by Bonferroni post hoc corrections. Alpha level of significance was set to 0.05. In addition, the values obtained were evaluated by calculating the effect size ( p G 2 ) and statistical power. Individual response analysis was performed in accordance to Sylta and colleagues (18) with percent differences categorized as nonresponse, G3% difference; moderate response, 3% to 9%; or large response, 99% difference. The Statistical Package for the Social Sciences (Version 24.0; SPSS Inc., Chicago, IL) was used for statistical analysis. Graphs were done in R-Studio (Version 1.1.383) and Excel 2010. RESULTS Descriptive data. The absolute pole length was 147 T 6cmrepresenting82.4%T0.9% of body height (measured with shoes). Females used shorter poles (both absolute and relative) compared with both elite males and junior level males (81.6% T0.8% vs 82.7% T0.8% and 82.9% T0.7%, P=0.048,P= 0.012). None of the skiers used a pole length greater than 83% of body height. Laboratory tests. For the laboratory tests, HR peak was 1.2% lower (range, j3.7% to 2.0%) with DP compared with DIA (190 T8 bpm vs 192 T7 bpm, P= 0.009) while relative and absolute V ˙O 2peak was 4.9% lower (range, j14.7% to +5.4%) with DP compared with DIA (67.3 T7.3 mLImin j1 Ikg j1 vs 70.8 T7.6 mLImin j1 Ikg j1 ;4.7T0.8 LImin j1 vs 5.0 T 0.8 LImin j1 ;bothP= 0.004). Peak blood lactate was similar between DP and DIA (10.4 T1.9 LImin j1 vs 10.6 T2.5 LImin j1 ; P= 0.664). Performance differences in the simulated outdoor competition. For the total group, the skiing time for the DP condition was nonsignificantly slower (14 T38 s) than CLASSIC (P= 0.116), but demonstrated a group– condition interaction (P= 0.009) with 2.8% (j24 s) faster skiing times in the male elite DP condition (P=0.018) and 3.9% (+43 s) slower skiing times in the female skiers DP condition (P= 0.035). Skiing times were similar between conditions for the junior males (P= 0.240) (Table 1). Mean skiing speeds for DP and CLASSIC were 5.5 T0.8 mIs j1 versus 5.6 T0.7 mIs j1 for the total group. Individual response analysis revealed that across the entire group 10% demonstrated a moderately positive response with DP only, 53% no difference, and 37% moderately negative response. Within the elite males, 50% demonstrated a moderate positive response in favor of DP and 50% achieved similar results between the two conditions. In the male juniors, 75% achieved similar performance and 25% achieved moderately worse performance with DP compared with CLASSIC. In females, 33% achieved similar performance between the two conditions, and 67% had moderately worse performance with DP (Fig. 2). Glide conditions were similar for DP and CLASSIC (13.51 T1.03 s vs 13.58 T0.81 s, P= 0.496). There was a low nonsignificant correlation between glide condition differences and delta changes in DP versus CLASSIC (r xy = 0.31, P= 0.25). Warm-up lactate was similar between both conditions (DP: 3.0 T 0.9 vs CLASSIC: 2.9 T1.2 mmolIL j1 ;P= 0.660). Section time and lap analyses. The time differences between DP versus CLASSIC within the single sections of the track for all three groups are illustrated in Figures 3A–C. In male juniors, none of the sections showed significant difference between DP versus CLASSIC. In the male elite, especially in the variable and moderate uphill terrain, DP was faster (P= 0.01 to 0.05) than CLASSIC. In the females, within all uphill sections, CLASSIC was faster (P= 0.001 to 0.005), whereas in the two steeper downhill sections, DP was faster (P= 0.013–0.026). When pooling the respective sections for the flat and moderately undulating terrain (variable terrain), the uphill sections (Up) and downhill sections (Down) and using the pooled data for DP and CLASSIC, the greatest differences between the three groups in total skiing performance were found in the uphill sections (interaction, terrain–group; PG0.001). http://www.acsm-msse.org764 Official Journal of the American College of Sports Medicine APPLIED SCIENCES More specifically, the greatest difference between DP versus CLASSIC between the three groups was found in the uphill section (interaction, condition–terrain–group: P= 0.025). The only difference between the three groups with respect to the comparison between DP versus CLASSIC was observed in the uphill sections (P= 0.001). No differences between groups were observed in the downhill and variable terrain sections. The difference between the two conditions in the uphill sections was most pronounced in females (61 T32 s slower with DP, P= 0.005) compared with nonsignificantly different values for DP and CLASSIC in both male elite (P= 0.162) and male juniors (P=0.116). FIGURE 2—Individual response analysis with respect to DP vs CLASSIC in the total group and the three subgroups. Percent differences are categorized as nonresponse, G3% or 9j3% difference; moderate positive response in favor of DP, 3% to 9%; moderate negative response in favor of CLASSIC, j3% to j9%. TABLE 1. Comparison of the situations DP vs CLASSIC for the Total group, EM group, JM group, and F skiers elite and junior skiers with respect to performance (time), blood lactate, and RPE. ANOVA Group DP CLASSIC Condition Group Group–Condition Skiing time (s) EM 842 T63 866 T59 a F 1,16 = 2.2 F 2,16 =31 F 2,16 =6.6 JM 911 T39 899 T47 N.S. PG0.001 P= 0.009 F 1158 T93 b 1115 T87 a,b p G 2 = 0.80 p G 2 = 0.47 Total 978 T147 964 T127 pow = 1.0 pow = 0.84 Lactate (mmolIL j1 ) EM 10.7 T3.1 9.4 T4.3 F 1,16 = 0.4 F 2,16 = 4.1 F 2,16 =2.9 JM 9.5 T1.2 10.4 T2.0 N.S. P= 0.036 N.S. F 7.0 T2.1 c 6.8 T0.7 d p G 2 = 0.34 Total 9.1 T2.5 9.0 T2.9 pow = 0.64 RPE WHOLE-BODY EM 16.4 T1.3 18.0 T2.0 F 1,16 = 1.6 F 2,16 = 0.9 F 2,16 =1.4 (6–12) JM 16.6 T1.2 16.6 T2.1 N.S. N.S. N.S. F 16.2 T1.0 16.2 T1.3 Total 16.4 T1.1 16.8 T1.9 RPE ARMS EM 16.6 T2.7 16.2 T2.6 F 1,16 = 2.2 F 2,16 = 0.2 F 2,16 =0.5 (6–12) JM 16.6 T1.2 16.6 T2.1 P= 0.027 N.S. N.S. F 16.6 T2.1 15.4 T1.3 p G 2 = 0.27 Total 16.5 T2.1 15.5 T1.8 a pow = 0.63 RPE TRUNK EM 15.2 T1.8 15.6 T1.3 F 1,16 = 0.3 F 2,16 = 0.02 F 2,16 =1.5 (6–12) JM 15.8 T1.5 15.1 T2.4 N.S. N.S. N.S. F 14.8 T1.2 15.7 T2.2 Total 15.3 T1.5 15.4 T2.0 RPE LEGS EM 15.2 T2.3 17.6 T1.5 F 1,16 = 8.8 F 2,16 = 2.3 F 2,16 =0.3 (6–12) JM 15.5 T1.8 16.8 T2.2 P= 0.009 N.S. N.S. F 14.0 T2.1 15.5 T1.0 p G 2 = 0.36 Total 15.0 T2.0 16.6 T1.8 a pow = 0.80 a Significantly different to DP. b Significantly different to both EM and JM. c Significantly different to EM d Significantly different to JM. Mean TSD. F, female; JM, junior male skiers; EM, elite male; Total, total group; p G 2 , partial eta squared effect size; pow, statistical power; N.S., not significantly different. DOUBLE POLING THE FUTURE TECHNIQUE? Medicine & Science in Sports & Exercise d 765 APPLIED SCIENCES Physiological and RPE differences between DP versus CLASSIC. There was no difference in HR mean , V ˙O 2mean ,V ˙O 2peak , tidal volume (V T ), RER, and blood lactate between the two conditions. HR peak was slightly lower with DP compared with CLASSIC (180 bpm vs 181 bpm, P= 0.032). In contrast, mean and peak breathing frequency was higher (P=0.015,P= 0.029) with DP compared with CLASSIC. Although there was no difference in RPE WHOLEBODY and RPE TRUNK (both P90.05), higher values were found for RPE LEGS with CLASSIC (P= 0.009) and for RPE ARMS with DP (P= 0.027). It should be noted that in the majority of significant results, the statistical power was G0.8. No group differences were found with respect to RPE values (all P90.05) (Tables 1 and 2.). The peak HR achieved during the two simulated races relative to the maximal HR achieved during the laboratory tests were 96% T6% versus 97% T5% for DP and CLASSIC, respectively, and 92% T17% versus 92% T14% for V ˙O 2 ,and 85% T29% versus 83% T30% for blood lactate. Pacing strategies (lap 1 versus lap 2 comparison). With the exception of three skiers, a positive pacing strategy with faster skiing times in lap 1 compared with lap 2 (pooled DP and CLASSIC: 478 T16 s vs 493 T16 s, PG0.001), with no interaction between conditions (DP vs CLASSIC) with respect to the decrement in performance across the laps was found (DP: 482 T77 vs 496 T71; CLASSIC: 475 T64 vs 489 T64 s, both P90.05). Both peak and mean HR increased from lap 1 to lap 2 (peak HR: 178 T7 bpm vs 183 T7bpm; mean HR, 173 T7vs178T6 bpm, both PG0.001). Only the mean V ˙O 2 and mean V T increased across the laps (mean V ˙O 2 , 56.7 T7.6 mLImin j1 Ikg j1 vs 60.5 T8.3 mLImin j1 Ikg j1 ;mean V T ,2.4T0.4 mLImin j1 Ikg j1 vs 2.6 T0.5 mLImin j1 Ikg j1 , both PG0.01), while V ˙O 2peak and V Tpeak remained constant. Breathing frequency and RER increased for both the mean FIGURE 3—Differences DP to CLASSIC in all three groupstfgap (A, male elite; B, male juniors; C, female elite). Red, CLASSIC faster; green,DP faster. a, first lap; b, second lap; *PG0.05, **PG0.01, ***PG0.001 significant difference between DP and CLASSIC within the respective section. http://www.acsm-msse.org766 Official Journal of the American College of Sports Medicine APPLIED SCIENCES and the peak values (mean, 54.4 T4.8 bpm vs 59.1 T5.6 bpm; PG0.001; peak, 62.3 T8.3 bpm vs 64.7 T8.8 bpm; P= 0.040). No significant interaction effects between condition and lap with sufficient statistical power were found for all measured parameters. DISCUSSION The main findings of the current study were sixfold: 1) total group differences between DP and CLASSIC were not observed with respect to performance, pacing strategies, or the majority of physiological parameters.; 2) within the three groups, the elite male skiers achieved higher, junior males similar and females worse performance with exclusive DP when compared with CLASSIC; 3) flat and undulating terrain favored DP in the male elite and male juniors, while the uphill sections were more advantageous with CLASSIC in females; 4) greatest discrepancies between performance groups were found in the uphill terrain for both overall performance (DP and CLASSIC pooled) and between DP and CLASSIC, with females demonstrating lower performance compared with the male skiers; 5) ski glide was not different between DP and CLASSIC and the difference in glide times was not related to the performance differences between the two conditions; and 6) analyzed skiers achieved DP V ˙O 2peak values of 95% (up to 105%) when compared with DIA V ˙O 2peak . Performance differences and section analysis DP versus CLASSIC. Within the total group, the application of exclusive DP with only glide-waxed skis resulted in nonsignificantly different race performance on a demanding XCS track fulfilling F.I.S. regulations when compared with CLASSIC. When analyzing the single groups separately, the male elite skiers were significantly faster (~23 s faster) with DP (demonstrating a moderate response), with no difference in junior male skiers and worse performance (~43 s) in female skiers. This result demonstrates that for DP to be beneficial over all classic techniques using grip-waxed skis, TABLE 2. Comparison of the situations DP vs CLASSIC for the Total group, the EM group, JM skiers, and F elite and junior skiers with respect to mean and peak valuesof physiological parameters. ANOVA Group DP CLASSIC Condition Group Group x Condition HR mean (bpm) EM 175 T3 175 T4F 1,16 = 1.6 N.S. F 2,16 = 0.6 N.S. F 2,16 =2.2 N.S.JM 178 T5 177 T7 F172T8 176 T10 Total 175 T6 176 T7 HR peak (bpm) EM 179 T4 179 T5F 1,16 = 5.5 P= 0.032 p G 2 = 0.26 pow = 0.60 F 2,16 = 1.6 N.S. F 2,16 =2.3 N.S.JM 183 T6 184 T7 F176T8 180 T9 Total 180 T7 181 T7 V ˙O 2mean (mLImin j1 Ikg j1 ) EM 62.4 T3.8 62.4 T3.4 F 1,16 = 0.2 N.S. F 2,16 = 1.2 N.S. F 2,16 =5.3 P= 0.027 p G 2 = 0.52 pow = 0.71 JM 56.9 T7.9 58.4 T8.9 F 56.5 T3.2 54.2 T1.2 Total 56.9 T7.9 58.4 T8.9 V ˙O 2peak (mLImin j1 Ikg j1 ) EM 66.9 T3.7 67.2 T3.8 F 1,16 = 0.02 N.S. F 2,16 = 2.1 N.S. F 2,16 =1.5 N.S.JM 66.5 T7.7 68.0 T6.9 F 60.8 T3.4 58.8 T1.5 Total 65.3 T6.0 65.7 T6.2 V Tmean (L) EM 2.5 T0.2 2.6 T0.3 a F 1,16 = 0.1 N.S. F 2,16 = 3.4 N.S. F 2,16 =3.3 N.S.JM 2.6 T0.3 2.7 T0.4 F 2.3 T0.3 2.0 T0.3 Total 2.5 T0.3 2.5 T0.5 V Tpeak (L) EM 2.7 T0.2 2.8 T0.2 F 1,16 = 1.3 N.S. F 2,16 = 7.9 P= 0.007 p G 2 = 0.59 pow = 0.88 F 2,16 =3.0 N.S.JM 3.0 T0.3 3.1 T0.4 F 2.5 T0.3 2.1 T0.4 Total 2.8 T0.4 2.8 T0.5 RF mean (bpm) EM 58.1 T4.1 55.6 T5.3 a F 1,16 = 8.2 P= 0.015 p G 2 = 0.43 pow = 0.74 F 2,16 = 0.0 N.S. F 1,16 =0.6 N.S.JM 58.2 T4.6 54.8 T5.5 a F 57.2 T2.9 56.1 T6.1 Total 58.0 T3.8 55.4 T5.1 RF peak (bpm) EM 64.1 T4.7 61.3 T7.5 F 1,16 = 6.5 P= 0.029 p G 2 = 0.40 pow = 0.64 F 2,16 = 0.2 N.S. F 2,16 =0.6 N.S.JM 67.2 T8.2 62.9 T10.2 F 63.1 T4.7 60.3 T6.2 Total 65.1 T6.1 61.7 T7.8 RQ mean EM 0.92 T0.04 0.90 T0.04 F 1,16 = 3.4 N.S. F 2,16 = 0.5 N.S. F 2,16 =0.5 N.S.JM 0.93 T0.11 0.95 T0.14 F 0.88 T0.05 0.90 T0.03 Total 0.91 T0.08 0.92 T0.10 RQ peak EM 0.95 T0.05 0.93 T0.04 F 1,16 = 2.3 N.S. F 2,16 = 0.9 N.S. F 2,16 =0.7 N.S.JM 0.97 T0.12 1.04 T0.15 F 0.93 T0.06 0.93 T0.04 Total 0.95 T0.08 1.00 T0.11 a Significantly different to DP. Mean TSD. RF, respiratory frequency. DOUBLE POLING THE FUTURE TECHNIQUE? Medicine & Science in Sports & Exercise d 767 APPLIED SCIENCES