REF-1559 · Walther et al., 2024 · International Journal of Sports Physiology and Performance · Paper · PubMed

How do world-class skiers reach more volume?

Over a career, from 124 to 197 double days a year and 441 to 519 sessions, self-reported, with more and longer easy sessions. Description, not proof doubles caused the rise.

Main caveat: Abstract only. No copy in PubMed Central or Europe PMC.
limited, mixed evidenceMeasured on world-class athletes

The authors compared the most successful junior and senior seasons of 15 world-class skiers using self-reported training. Each value is printed with a spread in square brackets; the abstract does not define the spread.

Total sessions rose (441 [71] to 519 [34], P < .001), mean duration rose (1.5 [0.1] to 1.7 [0.1] h, P < .001), and double-session days rose (124 [50] to 197 [29] days, P < .001). Low-intensity sessions rose in number and length (310 [64] to 393 [64]; 1.3 [0.1] to 1.5 [0.1] h).

Among hard sessions, the most frequent junior format was 20-39 min of high-intensity work with intervals under 5 min. At senior age it was 40-59 min of moderate-intensity work with 5-9-min intervals. High-intensity sessions fell (36 [17] to 25 [10], P = .027), which the authors say more mixed sessions (9 [7] to 14 [7], P = .023) and longer races made up for.

Our reading: in this rare group, the extra senior volume came with more easy sessions and more double days. Whether that is cause, consequence or both cannot be read from such data.

Protocol

Design: retrospective, two seasons each, chosen as the most successful junior and senior season. No control group.
Who: as above.
Data: self-reported training with form, intensity and exercise mode. The abstract does not give the source (diary or recall), the coding rules or the age at each season.
Analysis: statistical comparison of junior and senior values with effect sizes; methods beyond that are not in the abstract.
Funding and interests: not in what was read.

Key Results

MeasureJuniorSeniorP (effect)
Sessions per season441 [71]519 [34]< .001 (large)
Mean session duration (h)1.5 [0.1]1.7 [0.1]< .001 (moderate)
Double-session days124 [50]197 [29]< .001 (large)
Low-intensity sessions310 [64]393 [64]< .001 (large)
Low-intensity session duration (h)1.3 [0.1]1.5 [0.1]< .001 (moderate)
High-intensity sessions36 [17]25 [10].027 (moderate)
Mixed sessions (moderate plus high)9 [7]14 [7].023 (moderate)
Race duration (h)0.5 [0.1]0.6 [0.1]"0.29" as printed (moderate)
Strength session duration (h)0.6 [0.1]0.8 [0.2]"0.30" as printed (moderate)
Reporting. The abstract calls the strength increase significant and gives both last rows a moderate effect, while printing P = 0.29 and P = 0.30; these may be slips for .029 and .030 (our reading). They are reproduced here as printed.
Our arithmetic: 78 extra sessions and 73 extra double days are close to one for one, on group means. Session count times mean duration goes from roughly 660 to roughly 880 h; the abstract prints no annual hours here, and rounded means make this approximate.

Mechanisms

Measured: nothing physiological; the data are self-reported training.
Authors' interpretation: volume rose mainly through more and longer easy sessions and more frequent twice-a-day training, while intensive work shifted toward moderate intensity with longer intervals and longer sessions.
Inference: the same career stage brings full-time training, more recovery time and more experience, so the shift in doubles may follow what the athlete can now tolerate as well as drive it.

Practical Application

How do world-class skiers reach more volume? Over a career, from 124 to 197 double days a year and 441 to 519 sessions, self-reported, with more and longer easy sessions. Description, not proof doubles caused the rise.
Good for: describing where double days appear in the very top of an endurance sport, and that the rise came alongside more easy work rather than more high-intensity work.
Good for: a corrective on hard sessions. High-intensity sessions did not rise with age in this group; they fell, with more mixed sessions and longer races said by the authors to make up for it, and moderate-intensity formats became the most common.
Not good for: telling an amateur that doubles are how to improve. These athletes averaged about 441 sessions a year even as juniors.
Not good for: cause, because the sample holds only those who reached the top, with no one who trained alike and did not.
Not good for: what a double day should contain, or how far apart its sessions should be. Neither is in the abstract.
Not from this paper: who has the hours for doubles is decided in the base's guides on hours, not here.

Limitations

Abstract only. No copy in PubMed Central or Europe PMC.
Retrospective self-report, for seasons that may be many years old for some (inference); the abstract does not give the time since each season.
Survivor sample. World-class skiers only; no comparison with those who trained the same and did not reach that level.
Selected seasons. The best junior and best senior season are chosen after the fact, so they may not be typical of either age.
Confounded by age and career. Growth, professional status, training history and competition demands change along with session count.
Small n, mixed sex. Fifteen athletes, 8 men and 7 women, with no sex split in the abstract.
Printed P values for race and strength duration look wrong; see Key Results.
Not measured: physiology, performance, injury or illness in relation to double days.
How this entry was checked and changed
Why this level

(from the abstract) — an elite case series earns B by design, lowered one step for key methods missing in an abstract-only small study: how seasons were chosen and training coded was not read, the printed spread is undefined and two P values look wrong, and the data are retrospective self-report. No copy in PubMed Central or Europe PMC