Long-term development of performance, training characteristics, and maximal aerobic power in world-class cross-country skiers

Abstract

Cross-country (XC) skiing is an endurance sport that constitutes a cornerstone of the winter Olympic program. This weight-bearing and full-body movement activity is performed in different styles and sub-techniques to manage the demands of hilly terrain that XC-skiing races put on skiers. The competition formats include ~1.5 km sprint competitions and distance races ranging from 10 to 50 km, and these are conducted as both interval and mass start races. A wealth of research has investigated the physiology and training characteristics of world-class XC-skiers. Exceptional performances by world-class XC-skiers are accompanied with large amounts of endurance training and outstanding maximal aerobic power (VO2max). However, knowledge regarding the long-term development of junior athletes who ultimately reached world-class level is limited, and current talent development practice is based upon limited scientific evidence. The overall objective of this dissertation was therefore to investigate age of peak performance with preceding performance progression and the changes in training characteristics and maximal aerobic power from junior to senior peak age in world-class XCskiers. In study I, a quadratic curve was fitted to each elite XC-skier’s age and International Ski Federation (FIS) points (performance expressed relative to the best athlete) born between 1981 and 1991. The derived individual performance trends were used to estimate peak age and relative performance progression. Peak age was found to be ~26±2 years (mean±SD) in both sprint and distance events. Small sex differences (mean difference, ±95% confidence limits; 0.8, ±0.5 years, small, p=.001) were found in sprint events but not in distance events. Top performers (i.e., podium athletes in World Cup or international championships) reached peak age 1.6, ±0.6 years (moderate; p<.001) and 1.0, ±0.6 years (moderate; p<.001) later in distance and sprint events, respectively, compared to their lower-performing counterparts. Relative performance progression over the 5 preceding years to peak age was similar for both event types, but men improved more compared to women (distance: 8.8, ±5.4%, small; p=.002, sprint: 7.5, ±6.4%, small, p=.002) and top performers improved more compared to the others in distance (42.9, ±6.1%; large, p<.001) and sprint (26.9, ±6.6%, large, p<.001). Relative junior performance explained approximately 50% of the variation in peak performance. In study II retrospective analysis on self-reported training and VO2max tests of ten male and seven female world-class XC-skiers was undertaken, and their most successful junior and senior season were compared. Training data was analyzed according to training volume, intensity, form, and mode. The study revealed that total training volume increased by 203±130 h (35±31%; large; p<.001) from junior to senior. Junior training volume was not related to senior training volume but negatively associated with changes in training volume towards senior age. The largest increases were observed for low-intensity training (LIT) (186±115 h, large, p<.001), clearly ahead of moderate-intensity training (MIT) (13±7 h, large, p<.001), while high-intensity training (HIT) remained unchanged. Women escalated their strength training to a larger extent and engaged more in strength training during senior age compared to men. Women also applied more unspecific modes during senior age. The study also demonstrated sex differences in the development of maximal aerobic power. While men increased absolute and relative VO2max by 8±5% (large, p=.009) and 6±4% (large, p=.016), a significant increase was only observed for relative VO2max in women (7±5%, large, p=.012). In study III designs and distribution of self-reported training session data of eight male and seven female world-class XC-skiers during their most successful junior and senior season were analyzed. The study showed that both the total number of sessions and the mean duration increased from junior to senior age (441±71 vs. 519±34 sessions, large, p<.001 and 1.5±0.1 h vs. 1.7±0.1 h, moderate, p<.001, respectively). This increase was due to more double-session days, while the number of training days remained unchanged. More and longer LIT sessions (especially LIT sessions lasting ≥90 min performed in specific modes) accounted for the largest part of the increase in training volume. HIT sessions with 20-39 min total work duration and <5 min intervals constituted the most common intensive session design at junior age, whereas 40-59 min MIT sessions and 5-9 min intervals were most frequently applied session designs at senior age. This thesis provides novel understanding on the long-term development of training characteristcs, maximal aerobic power and performance among world-class XC-skiers. The presented results may function as useful background information and framework for athletes, coaches and sport federations in processes associated with goal setting, talent development benchmarking, athlete selection, allocation of funding and resources and long-term training planning. The findings may also provide a starting point for future research planning to explore mechanisms tied to the long-term training and development of talented endurance athletes.