Cross-country (XC) skiing is a biomechanically complex sport that relies on individuals using their arms and legs in a coordinated manner to successfully perform a range of techniques according to skiing condition, speed, and individual preference. An XC skiing technique can be classified as “symmetric” or “asymmetric.” In symmetric techniques, both sides of the body work in symmetry either simultaneously (e.g., right and left upper extremities move and apply forces simultaneously in double poling) or diagonally (e.g., upper and contralateral lower extremities move together during diagonal striding). In asymmetrical XC skiing techniques, the right and the left sides of the body function in asymmetry or asynchrony that results in differential force application through the right and left poles and/or legs.
The two asymmetric techniques in XC skiing are the V1 and the V2 alternate skate techniques, in which pole support is used only on one side of the body during leg push-off. As depicted in Figure 1, the V1 skate technique is primarily used when ascending steep hills and the V2 alternate skate technique moreover on level or slightly downhill terrain. Skiers can choose to use either a right or a left pole-supporting side in both of these skating techniques, with the preferred side often called the strong or dominant side and the nonselected side termed the weak or nondominant side (11,20,21).
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FIGURE 1: Schematization of the V1 skate technique (A) and the V2 alternate skate technique (B) used in XC skiing.
Elite XC skiers spend approximately 50% of their racing times on uphill terrain (2,5). Thus, how well skiers master the V1 skate technique is a key determinant of overall race finishing time. Although most elite XC skiers are able to use either side for pole support without noticeable difficulties, skiers tend to demonstrate a bias toward one side at high intensity or in a state of fatigue. Although such side preference is observed in XC skiing, there are no scientific publications to our knowledge reporting the side preference frequency for V1 skate, its determinants, or the resulting differences in performance in elite XC skiers.
Although not yet specifically addressed in XC skiers, for more than 40 yr, neuropsychology has explored side preference in individuals primarily using standardized questionnaires (3,12). The latter questionnaires have been adapted for use in sports science. Handedness is conventionally reported in sporting activities that rely on the use of the upper body for throwing or striking objects (15,19), whereas footedness is investigated in sports that require the lower body for kicking or lower extremity for cyclic tasks (6,7). In XC skiing, it seems important to document both handedness and footedness, considering that the activity depends on the combined use of arms and legs for performance. However, neither handedness nor footedness has been documented in the scientific XC skiing literature.
Furthermore, dominance, asymmetry, and right- to left-side differences are reported as considerable risk factors to musculoskeletal injuries in given population groups and when performing particular activities (10,16). Indeed, a recent study including young recreational female alpine skiers found that injuries were more frequent in the left than right lower extremity (18). The authors suggested that laterality or side-to-side differences were the most likely explanation to their findings, but no further empirical data were available to confirm their assumption. The repetitive loading of the body during XC skiing is reported to contribute to the high prevalence of low back pain in this population (4). Low back pain or other musculoskeletal injures during sports may result from asymmetric force application or repeated asymmetric body motion. Yet again, this aspect has not been thoroughly explored or reported in the XC skiing literature.
The underlying question to the current study was “What might explain V1 skate side preference in elite XC skiers?” Therefore, the purpose was to investigate V1 side preference in elite XC skiers, notably through the documentation of V1 skate side preference, dominant and nondominant V1peak speeds, left- to right-side differences (ΔL-R) in laboratory-based measurements, and relationships between side preference data. The main hypotheses were as follows: 1) more skiers prefer the right side when using the V1 skate technique, 2) skiers exhibit greater V1peak speeds on their dominant versus nondominant sides, and 3) ΔL-R in V1peak speeds correlate to ΔL-R in laboratory-based measurements (e.g., higher V1peak speed, higher pole forces, and greater lean body mass content on skiers’ dominant side).
METHODS
Subjects
Sixteen male elite sprint XC skiers (mean ± SD; age = 26.6 ± 4.6 yr, body mass = 76.1 ± 5.2 kg, body height = 180.0 ± 4.7 cm), including national-level (n = 6) and international-level (n = 10) skiers from the Swedish, Austrian, and Norwegian national teams, volunteered to participate in this study. The group included one medalist from the Sprint World Championship, one medalist from the overall Sprint World Cup, three World Cup winners, and nine skiers with top 20 rankings in the World Cup. One of the subjects was a classic specialist, four were experts in sprint skating, six others competed in both sprint and distance races on an international level, and the remaining skiers were cross-disciplinary athletes. All subjects were fully acquainted with the nature of the study before they gave their verbal and written informed consent. The study was approved by the ethics committee of the Umeå University, Umeå, Sweden (no. 08-058M).
Overview of the testing procedure
Subjects were tested on two separate days within 1 wk. Day 1 consisted of a whole-body DXA scan to collect anthropometric data. On the second day, subjects performed two incremental speed tests roller-skiing on a treadmill. One speed test was performed using the V1 skate technique with the dominant side and the other test using the V1 skate technique with the nondominant side. The sequence of V1-dominant and V1-nondominant testing was randomized to minimize order bias and limit the potential influence of fatigue from the first test session on to the second test session. During the speed tests, V1peak speed and time to exhaustion were measured, as were biomechanical data of pole and plantar forces at the highest speed increment that all of the skiers were able to complete on both V1-dominant and V1-nondominant sides (15 km·h−1). In addition, all subjects answered a standardized form with questions about side preference during V1 and V2 alternate skate techniques, various XC skiing techniques and maneuvers, handedness, and footedness. Injury data were also recorded. An overview of the data collection process is provided in Figure 2.
FIGURE 2: Schematic representation of the data collection process.
Anthropometric measurements
Body composition including total mass, lean mass, fat mass, and bone mass content and body dimensions of the right and left body sides were analyzed for the whole body, trunk, legs, and arms using the DXA software (Encore 2007, Version 11.4; General Electric Company, Madison, WI) following similar procedures to a previous study (21). All DXA measurements were performed in a fasted state (no food or liquid intake for 8 h before measurement). The equipment was calibrated before each test using a phantom and standardized procedure. Lean, fat, and bone mass values for the whole body and for the single segments were reported as absolute and relative values (% body mass and % segment mass).
Biomechanical measurements
The incremental speed tests were performed on a large roller-skiing treadmill (belt dimension 3.3 × 2.5 m; Rodby, Sodertalje, Sweden). All subjects had previous experience with roller-skiing on the treadmill and the applied test concepts as part of their seasonal training and performance testing. For safety reasons, subjects wore a pelvic belt that was attached to a metal bracket suspended above the treadmill and connected to an emergency brake. All the incremental speed tests started with a 15-min standardized warm-up using the specific XC skiing technique. This included a standard 10-min low intensity roller-skiing using the V1 skate technique, followed by four 6-s sprints during the last 5-min period of the warm-up. A 3-min break period followed the warm-up before beginning the incremental speed test. Between the two V1 incremental speed tests, subjects performed a standard 10 min of low-intensity roller-skiing using the V2 skate technique, a symmetrical skating technique, for recovery. After this active recovery period, subjects had a 20-min break before the start of the warm-up for the second incremental speed test.
The incremental speed tests were performed to exhaustion to determine subjects’ V1peak speed on their dominant and nondominant sides. The test protocol was based on previously established and validated experimental protocols from Stöggl et al. (22). The tests were performed on a treadmill at a grade of 7°. The initial speed was 12 km·h−1 and was increased every 10 s at increments of 1 km·h−1 until exhaustion. Exhaustion was defined as an inability to maintain the given speed on the treadmill. Thus, the incremental speed tests were stopped by the tester when the subjects passed a marker placed at a distance of 1.5 m behind the front of the treadmill. V1peak speed from each of the two incremental speed tests was calculated by linear interpolation using the following formula: V1peak speed = Vf + [ ( t / 10) ΔV], where Vf is the speed of the last completed workload, t is the duration of the last workload (s), and ΔV is the speed difference between the last two completed workloads.
All subjects used Pro-Ski S2 roller-skis (Sterners, Nyhammar, Sweden) with a rolling resistance friction coefficients of μR = 0.013 measured on the treadmill surface in a fixture specially designed for this purpose (1). Testing was performed with carbon-fiber racing poles specially constructed for force measurements during XC skiing. The poles were adjustable, enabling each subject to set the poles to their preferred length. A strain gauge force transducer (Hottinger-Baldwin Messtechnik GmbH, Darmstadt, Germany) mounted directly below the pole grip measured the pole reaction force in the axial direction. The transducer weighed 60 g and was installed in a lightweight (75 g) aluminum tube. Plantar insoles inserted into the right and left XC ski boots recorded plantar ski reaction forces at 100 Hz (Pedar mobile system; Novel GmbH, Munich, Germany). The validation and the calibration of the pole and plantar force measurement systems were achieved using the procedures described by Holmberg et al. (13)
Biomechanical data collection and management
Pole force data were recorded using a 3000-Hz sampling frequency, amplified via a telemetric recording system (TeleMyo 2400T G2; Noraxon, Scottsdale, AZ), and transferred to a personal computer through an analog/digital converter card. Synchronization between pole and plantar forces was achieved by using a synchronization signal produced by the start of the Pedar mobile system. The complete measurement equipment weighed 1.5 kg and was securely fastened to subjects using a hip belt that did not impede XC skiing movement. For analysis, 10 consecutive cycles of pole and plantar force data were extracted from the last 10 s of the 15-km·h−1 submaximal stage during the incremental speed test. Peak pole and peak plantar forces along with pole and plantar force impulses were separately calculated for the right and left sides of the body. Biomechanical data were also used to determine cycle characteristics (i.e., cycle rate, cycle length, swing times, and recovery times). All data processing was managed using IKE master software (IKE-Software Solutions, Salzburg, Austria).
Questionnaire
Handedness data were collected using the items from the Annett Hand Preference Questionnaire (3), and footedness data were collected using the Waterloo Footedness Questionnaire–Revised (9). A seven-item laterality questionnaire specific to side preference during XC skiing was designed according to handedness, footedness, and other sport-specific laterality items (6,17). The self-reported side preference in V1 skate and V2 alternate skate techniques were of particular interest. To provide further insight into side choice in the V1 skate technique, an additional four questions specific to this technique were included and focused on skiing speeds. Finally, right- and left-sided injury data were obtained from a series of 11 questions covering all body segments. The four questionnaires (handedness, footedness, ski-specific, and injury) were administered as one, in which each question could be answered with “right,” “left,” or “either” based on the preferred side used for performing a given task (e.g., write, kick a ball, and ski curve) or the side with an ongoing or previous injury. An overall right, left, or either side laterality score was given for handedness, footedness, XC skiing, and injury based on the highest response frequency in each independent questionnaire.
Statistical analysis
Anthropometric and biomechanical data are presented as means ± SD and were normally distributed according to results from the Shapiro–Wilk test. A paired sample t-test was applied to determine differences in V1peak speeds between dominant and nondominant sides. Pearson product moment correlation (r) was used to determine whether ΔL-R in V1peak speed was correlated to ΔL-R in anthropometric (i.e., body composition and dimensions) and biomechanical measurements (i.e., pole and plantar forces from each V1 technique at the submaximal speed). Because of the asymmetric application of pole and plantar forces when using the V1 skate technique given the presence of a strong and weak side, the left pole–left plantar forces during V1left was compared with the right pole–right plantar forces during V1right for strong side comparisons, and vice versa for weak side comparisons. Phi and Lambda correlation coefficients were applied to establish whether the dominant side in the asymmetric skating techniques, V1 and V2 alternate, correlated to the questionnaire data. According to Hopkins et al. (14), the correlation coefficients were categorized as follows: extra large, >0.7; large, 0.5–0.7; moderate, 0.3–0.5; and low, <0.3. Finally, standard one- and two-sample tests of proportions were used to determine whether the distribution of dominance in skiers was equivalent in different skiing situations. The level of statistical significance was set to α < 0.05 for all analyses. All statistical tests were processed using the Statistical Package for the Social Sciences (Version 20.0; SPSS Inc., Chicago, IL) and Office Excel 2010 (Microsoft Corporation, Redmond, WA).
RESULTS
Laboratory
No significant difference in side preference when using the V1 skate technique among skiers was found. Of the 16 subjects, 7 selected the right side (44%) and 9 selected the left side (56%) (P > 0.05). Subjects were approximately 4.5% faster (17.0 ± 1.0 vs 17.7 ± 0.8 km·h−1, P < 0.001) and had approximately 15% longer test durations (49.7 ± 10.0 vs 57.2 ± 8.3 s, P < 0.001) when using their dominant side, with 2 of the 16 subjects skiing slightly faster and for a longer duration when using their nondominant side. The difference in V1peak speeds between dominant and nondominant sides ranged from 2.14 (14.7%) to −0.08 km·h−1 (−0.5%) in skiers with a moderate correlation between V1peak speeds recorded using the dominant and nondominant side (r = 0.69, P < 0.01) (Fig. 3). Independent of the preferred side, across the skiers, V1peak speed for the left side was not different to V1peak speed for the right side (17.4 ± 0.9 vs 17.2 ± 1.1 km·h−1, P > 0.05).
FIGURE 3: Relationship between V1peak speeds on the dominant side and nondominant side. r xy, Pearson product moment correlation coefficient. R 2, coefficient of determination.
When skiing with V1-dominant side, subjects demonstrated 4.2% longer cycle lengths (4.25 ± 0.16 vs 4.08 ± 0.25 m, P < 0.01) with 4.9% lower cycle rates (0.98 ± 0.04 vs 1.03 ± 0.06 Hz, P < 0.01), 3.5% longer leg ground contact times (0.59 ± 0.03 vs 0.57 ± 0.04 s, P < 0.05), 6.7% longer arm swing times (0.64 ± 0.04 vs 0.60 ± 0.06 s, P < 0.01), and 4.9% longer leg swing times (0.43 ± 0.03 vs 0.41 ± 0.04 s, P < 0.01) when compared with skiing on the V1-nondominant side. No differences between V1-dominant versus V1-nondominant sides were found for poling times and pole and leg forces.
Table 1 presents the mean and range of the ΔL-R from all recorded anthropometric and biomechanical measurements. The pole force impulse on the strong side during the V1 skate technique was 81% ± 77% higher than the pole impulse force on the weak side (56 ± 13 N·s vs 33 ± 7 N·s, P < 0.001), whereas no difference was observed for strong and weak sides in the plantar forces (330 ± 73 N·s vs 328 ± 55 N·s, P > 0.05) during the V1 skate technique. ΔL-R in V1peak speed were positively related to ΔL-R in peak pole force of the left pole of V1left and of the right pole of V1right (r = 0.69, P < 0.01). No similar relationships between ΔL-R in V1peak speed and ΔL-R in plantar forces were found. No significant correlations between ΔL-R in body composition and dimensions and ΔL-R in Vpeak speed, pole force data, or plantar force data were observed. None of the absolute ΔL-R in measurements correlated to V1peak speed.
TABLE 1: ΔL-R in anthropometric and biomechanical measurements.
Questionnaire
A summary of the answers provided to the specific questions on side preference during XC skiing is presented in Table 2. The side that subjects used to perform the incremental speed test using the V1 skate technique on the dominant side was the same as the self-reported dominant side for V1 in the questionnaire. Hence, seven and nine subjects reported right- and left-side preferences when using the V1 skate technique, respectively. In contrast, 10 subjects (62%) reported a right-side preference when using the V2 alternate skate technique, with the remaining six (38%) reporting a left-side preference (P < 0.05). The dominant side used for the V1 skate technique was positively correlated to the dominant side used for the V2 alternate skate technique (Phi = 0.78, P < 0.001).
TABLE 2: Side preference in elite XC skiers (n = 16).
Eleven skiers (69%) were categorized as being overall right-side dominant skiers with the remaining five (31%) classified as being overall left-side dominant skiers. Fourteen skiers (88%) were right-handed and two (12%) were left-handed. The same proportions of skiers were determined to be right and left footed. The dominant side when using the V1 skate and the V2 alternate skate techniques were positively correlated to the overall skiing dominance determined using the questionnaire (phi = 0.67, P < 0.01 and phi = 0.59, P < 0.05). No correlations between the dominant side reported for V1 or V2 alternate skating techniques and side for handedness, footedness, or injury were found; neither between overall skiing dominant side and side determined for handedness or footedness (phi = 0.15, P > 0.05).
From the questionnaire data, it was found that side preference was reported at moderate skiing speeds in 11 subjects (69%), at 15-km endurance-race speeds in 13 subjects (81%), and at sprint-race and maximal speeds in all 16 subjects (100%) when using the V1 and V2 alternate skate techniques (P < 0.05). Eleven subjects (69%) reported a preferred kicking leg when using the kick double poling and diagonal stride techniques, with five subjects (31%) having no side preference. When performing a transition from double poling to diagonal stride or from double poling to kick double poling, only one subject reported no side preference regarding the kicking leg. All subjects reported preferred sides for taking a curve when skiing rapidly, stopping quickly during skiing, and pushing a leg forward when crossing the finish line of a ski race.
DISCUSSION
The main findings of the current study are as follows: 1) side preferences in the V1 and V2 alternate skate techniques were documented, with equal left- to right-side distributions for the V1 skate technique and a slightly greater number of skiers preferring the right to the left side when using the V2 alternate skate technique; 2) subjects were approximately 4.5% faster when skiing using the V1 skate technique on their dominant versus nondominant side, with a moderate correlation between V1peak speed on the dominant and V1peak speed on the nondominant side; 3) none of the ΔL-R in anthropometric and biomechanical measurements were related to V1peak speed; 4) V1-dominant side was correlated to both V2 alternate and overall skiing dominant sides; but not to handedness, footedness, nor side of the body with the higher injury prevalence; 5) reporting a dominant side increased as skiing speed increased from moderate to sprint speeds in the two asymmetrical XC skating techniques; and 6) a preferred side in several XC skiing tasks was discerned through the ski-specific questionnaire, but no evident pattern or association between side preference during XC skiing, handedness, footedness, and number of one-sided injuries was found. Overall, because of the lack of systematic relationships between measured side-to-side differences in the present data set, side preferences and dominance seem to be highly specific to tasks, including the V1 skate technique in elite XC skiers.
The current study is the first to report aspects of dominance in elite XC skiers. It clearly demonstrated that skiers prefer one side over the other in asymmetric skating techniques as well as in other XC skiing maneuvers and tasks. Declared dominant sides were right in 44% of subjects for V1 and 62% for V2 alternate skate techniques, with a moderate correlation between reported dominant sides within these two asymmetric skating techniques. Subjects were able to reach approximately 4.5% (0.7 km·h−1) higher V1peak speeds on their dominant compared with nondominant sides. However, the difference in V1peak speed within the group ranged from 2.14 km·h−1 faster (14.8%) to 0.08 km·h−1 slower (−0.5%) when using the dominant side, with two subjects being faster on their nondominant side and five having similar V1peak speeds on both dominant and nondominant sides (line of identity; Fig. 3). When analyzing the individual values in V1peak speed differences, no clear linkage toward the skiers background (competitors in sprint only, both sprint and distance, classic vs skating specialists) was visible. It was interesting to find that a subject’s preferential side increased with skiing speed. A total of 69% of subjects reported a side preference at moderate speeds, which increased to 81% at a 15-km endurance-race speed and to 100% at sprint-race or maximal speeds. Therefore, it might be speculated that focusing on sprint skiing—implying a greater amount of training at high to maximal skiing speeds—emphasizes dominance or side selection in XC skiing. Recently, it was demonstrated that during a simulated sprint race on snow using the skating technique, skiers solely used their dominant side with no change to the nondominant side in both V1 and V2 alternate skate techniques (2). The lack of side changes during sprint skiing might be attributed toward the benefit of 4% (up to 15%) higher peak speeds with V1-dominant side. Although the latter supports the speculation from the current findings that skiing discipline and speed play a role in the expression of side preference in XC skiing, a future study focusing on investigating differences between distance and sprint skiers in regard to side preference is required to further understand determinants to laterality in this sport.
A large correlation (r = 0.69) was identified between the dominant and the nondominant sides for V1peak speed. This indicates that V1peak speed on the dominant side explains V1peak speed on the nondominant side by approximately 48%. Hence, V1peak performance on one side does not entirely predict skiers’ performance on the other side. This is illustrated in Figure 3, where both fast and slow skiers show distinct differences in V1peak speeds on their respective dominant and nondominant sides. Indeed, some skiers demonstrated large differences in V1peak speeds between sides, whereas others had quite similar levels of performance. Contrary to what may be expected, the amount of symmetry or asymmetry in V1peak speed on the dominant and nondominant sides was not related to the absolute level of performance with V1-dominant side. However, asymmetry may have been detrimental to other performance factors that were not investigated here, considering that analyses were constrained to laboratory settings. In the current study, the skiers were analyzed on a treadmill under experimental conditions that do not account for change in terrain, meteorology, and skiing direction. For instance, depending on the profile of a track, the ability to change between left and right sides in XC skiing might be a decisive factor in race outcome. The choice of side is regulated in part by skiing speed and course topography (e.g., side hill and curve directions on flats or inclines). For instance, while skiing uphill using the V1 skate technique on a track hanging to the left, it is recommended to use the right side (V1right) for better performance. Therefore, skiers that usually use V1right would have a tactical and technical advantage over skiers that prefer to use their left side (V1left). It is worth noting that the mean difference of 4%—reaching up to 15%—in peak speed between V1-dominant versus V1-nondominant sides might have a considerable effect on performance outcome over the course of a track with varying terrain (curves, side hills, etc.), especially in distance events.
Considering the effect that the aforementioned differences could have in XC skiers’ race results, ΔL-R and overall side preference in XC skiing might provide a useful measure in performance diagnostics and race or training preparation. In fact, the cycle rates were higher and the cycle lengths were shorter when skiing using the V1 skate technique on the nondominant side, which were linked with reduced swing times. However, the resultant forces of both legs and arms were not different when compared with V1-dominant side. These latter two biomechanical findings most likely indicate a less effective technique strategy with lower generation of propulsive forces at equal force inputs during the V1 skate technique on the nondominant side, leading to a less economical skiing technique (e.g., higher cycle rate with shorter recovery phases). Furthermore, ΔL-R in V1peak speed were positively related to ΔL-R in the peak pole force of the left pole of V1left and the right pole of V1right. Hence, skiers with greater differences in peak speeds also demonstrated greater differences in their strong side pole forces. Consequently, skiers with imbalances between V1-dominant versus V1-nondominant performances might benefit from regular training with their nondominant side, combined with technical training with feedback concerning force application, propulsive force generation, and cycle characteristics.
Switching sides when using a given technique is encouraged to unload the structures and muscles of one side of the body, thereby shifting the demands to the alternate side and potentially postponing fatigue. In this context, it is worth noting that the pole force impulse on the strong side during the V1 skate technique was 81% higher than the pole impulse force on the weak side, whereas no difference was visible for strong and weak sides in the plantar forces. Therefore, the proposition that switching from V1-dominant to V1-nondominant sides to off-load structures and alter force application is coherent with the current study results in regard to the upper extremity, but not so clearly for the lower extremity. Such aspects have never been explicitly quantified in the scientific literature, and the unloading of sides was primarily based on anecdotal observations and recommendations from coaches, athletes, or health professionals. Therefore, the current study is the first to highlight these aspects of dominance and side differences in XC skiing and their associations with performance.
In sports other than XC skiing, laterality is often termed as being a risk factor to injury (10,16). Although it is believed that the preferential use of one side over another or asymmetries in biomechanical measurements in sport-related tasks can predispose an athlete to an injury (16,23), the current study identified that side preference in asymmetric skating techniques was not related to the occurrence of injury to one side of the body. The existence of a dominant side in the V1 skate technique, in addition to differences in peak speeds and pole and plantar forces between sides, showed no direct association to injury in contrast to what may have been expected.
Elsewhere, the dominant side used in the V1 skate technique was only related to the dominant side used in the V2 alternate skate technique and overall skiing dominance. There were no other correlations to the V1-dominant side when considering the other measurements, such as handedness, footedness, injury, and anthropometric. Therefore, it seems reasonable to state that within XC skiing itself, there is a global side preference; however, more specific or common measures of side preference and laterality demonstrate no significant association with side preference in XC skiing. Consequently, the question “why is there a dominant side in XC skiing?” cannot be clearly answered yet based on the multifactorial approach undertaken in this study and its resulting findings. A valid assumption was that the existence of a dominant side in XC skiers would relate or lead to side differences in anthropometric (e.g., lean mass and bone mass content). However, this was not the case. The lack of association between measurements might be due to the subjects’ high performance level because all subjects were used to training both sides of their body during—and outside of—XC skiing. However, in a cohort of amateur skiers, the different aspects of laterality investigated here might have a distinct effect on side preference during XC skiing and might be reflected in individual anthropometric and biomechanical measurements.
One interesting finding was that within the single measures of laterality, hardly any correlations were found. For example, there were no significant relationships established from the biomechanical measurements in regard to ΔL-R pole and plantar forces during the V1 skate technique using the dominant compared with the nondominant sides. These findings highlight the distinct biomechanical features within this asymmetric technique, emphasizing that the recruitment patterns and force applications established on one side are not generalized to the other side. As recently suggested (8), symmetry cannot be assumed between dominant and nondominant sides. The lack of correlation between ΔL-R of the separate measurements questions whether establishing side differences and dominance in elite XC skiers truly relates to their side preferences and overall performance levels. Aspects of dominance seem to depend strongly on the specific measurement situation and are highly task oriented, and the generalization to sport-specific situation is doubtful.
A laterality questionnaire was developed to collect data concerning side preference specific to XC skiing techniques and situations usually encountered during this sport. From this seven-item questionnaire, 11 skiers (69%) were categorized as being overall right-side dominant skiers, and the remaining 5 skiers (31%) were classified as being left-side dominant. These overall dominant sides identified during XC skiing did not correlate to the dominant hand or the dominant foot determined from validated questionnaires (3,9). Handedness and footedness were limited in explaining side preference in asymmetric skating techniques in this cohort of elite skiers. Further understanding of lateralization in XC skiing is proposed through the development and use of a more extensive ski-specific laterality tool in biomechanics and the undertaking of neuromuscular control investigations.
CONCLUSIONS
In summary, some moderate correlations between aspects of laterality in elite XC skiers were determined, but there was no systematic relationship between measurements and ΔL-R. The findings from the current investigation demonstrate that side preference and left-to-right differences in this sport is multifactorial; shows individual variation; and is not highly correlated to V1peak speed, anthropometric, biomechanical measurements, handedness, footedness, or injuries. Side preference seems to be highly specific to the exercise task and generalization toward XC skiing techniques, and skill is not certain. Research into other influential factors on side preference in XC skiing—including coaching methods, skiing experience, and training regimen—is recommended to further its understanding.
This investigation was financially supported by the Swedish National Centre of Research in Sports (CIF).
The authors thank the athletes, trainers, and research assistants involved in this study for their participation, enthusiasm, and cooperation.
None of the authors had any personal or financial conflicts of interest.
The findings of this study do not constitute endorsement by the American College of Sports Medicine.
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