Pith. sign in

REVIEW 3 major objections 4 minor 9 references

The Fast and the Furious: Tracking the Effect of the Tomoa Skip on Speed Climbing

T0 review · 3 major / 4 minor · reviewed 2026-08-12 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read Using the Tomoa Skip in speed climbing is associated with roughly a 15 percent reduction in a climber's best time, after accounting for gender, age, and time trends in a mixed-effects model of IFSC results from 2012 to 2022.

arxiv 2411.13696 v1 pith:O5ITBQ7T submitted 2024-11-20 stat.AP

Caleb Chou , Andee Kaplan This is my paper · ORCID
classification stat.AP
keywords speedclimbingTomoaSkipmixedeffectsmodelsportstatisticsOlympicperformanceanalysistechniqueinnovationIFSC
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper sets out to measure whether the Tomoa Skip, a dynamic step-up move that bypasses the second handhold of the 15-meter speed wall, made climbers faster and whether it made them less reliable. Watching 54 broadcast finals and combining that with IFSC results, the authors fit mixed-effects models to each climber's best time per event. They find that using the skip is associated with a multiplicative time change of 0.8549 (95% CI 0.8271, 0.8836), i.e., about 14.5% faster, after controlling for gender, age, and the general historical improvement in times. They do not find a statistically significant relationship between skip usage and falling in finals. If the estimate is right, the move that boulderer Tomoa Narasaki introduced into speed climbing offers a large competitive edge and helps explain the rapid succession of world records after 2018.

What carries the argument

The argument is carried by a two-level mixed-effects model fitted to log-transformed best times, with random intercepts and random slopes for Tomoa Skip usage varying by both climber and event. Exponentiating the fixed coefficient for skip usage yields the multiplicative effect on time, and the log link is what turns the model into a statement about percentage change. The predictor itself was built by manually labeling skip use from 54 IFSC broadcast finals and then forward-filling the binary indicator: a climber observed doing the Tomoa Skip in one final is assumed to use it in all later events (and in unobserved qualifying rounds), with the reverse applied for the one climber documented switching away from it.

What would settle it

Obtain full per-attempt Tomoa Skip usage for all rounds (not just finals) of IFSC speed events from 2018-2022, re-estimate the paper's mixed model with the actual usage indicator instead of the forward-filled one, and check whether the Tomoa Skip coefficient's 95% confidence interval still excludes 1. If it includes 1 (no multiplicative change), the central claim is falsified.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is that the Tomoa Skip confers a substantial speed advantage: the estimated fixed effect of using the move is -0.1568 on the log-time scale, which back-transforms to a 0.8549-times multiplicative change in a climber's expected best time (95% CI 0.8271 to 0.8836). Interpreted concretely, a 7-second climb without the skip is predicted to become roughly 5.98 seconds with it. This estimate comes from a model that includes random intercepts and random skip slopes for both climbers and events, together with fixed effects for gender, age, and a time-progression variable, and the outcome is the logarithm of the climber's fastest time in any round of each event. The paper also reports that in a binomial generalized mixed model, skip usage has no statistically significant association with the probability of falling in a final round, although descriptive plots show wider within-event time ranges for early skip adopters.

Load-bearing premise

The central assumption is that a climber documented using the Tomoa Skip in one broadcast final is using it in every other round and future competition; if usage actually varies, the main predictor is misclassified and the estimated 0.8549 time multiplier could be biased.

Editorial extensions

If this is right

  • If the association is causal, climbers who have not adopted the skip are racing with an effective handicap of roughly 15% on their best time, far larger than the margins that decide finals.
  • Because adoption was still incomplete at the end of 2022, the average effect estimated on early adopters implies the sport's baseline speed should keep shifting downward as the move becomes universal.
  • The absence of a significant fall effect suggests the skip is not a riskier strategy on average, which supports its use as a standard technique rather than a gamble.
  • The finding implies the Olympic combined format, by forcing boulderers into speed climbing, produced a lasting technique transfer that likely contributed to the post-2018 wave of world records.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The forward-filling assumption is the main vulnerability: if climbers sometimes try the skip in finals but abandon it in qualifying or later events, the predictor is misclassified and the estimated effect could be biased in either direction; a testable extension is to label every attempt from full-event video and re-estimate with a time-varying skip indicator.
  • Because skip adoption is voluntary, the model does not fully rule out selection bias—stronger, more adaptive climbers may have adopted the move earlier—so a within-climber pre/post design with event fixed effects would be a sharper causal test.
  • The paper's consistency analysis conflates within-event range with consistency; a variance-model extension (e.g., a mixed-effects location-scale model) could formally test whether skip users have higher performance variance, not just wider ranges in early events.
  • The record-breaking narrative is descriptive; a changepoint or intervention analysis on world-record times could statistically separate the skip's introduction from the general training and hold-technology improvements.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 4 minor

Summary. The paper investigates the effect of the Tomoa Skip on IFSC speed climbing times using scraping of competition results from 2012 to 2022 and manual coding of Tomoa Skip usage from 54 YouTube broadcasts of finals (2018-2022). TS usage is imputed forward and backward under a persistence assumption. The authors fit mixed effects models with log best time as the outcome, fixed effects for TS, gender, age, and time progression, and random intercepts and random TS slopes for climbers and events. Model M3 is selected by BIC and ANOVA, yielding a fixed TS coefficient of -0.1568 (95% CI: -0.1898, -0.1238), corresponding to a multiplicative 0.8549 change in average best time. The paper also examines variability of times and a generalized mixed model for falls, finding no significant fall effect.

Significance. If the central estimate is accepted, the paper provides a quantitative measure of a novel technique's impact in a sport with limited quantitative analysis, and the confidence interval is reasonably tight. The manual video coding of 108 hours of footage is a substantial data collection effort, and the model is a sensible starting point for this question. However, the causal interpretation is fragile: TS adoption is observational and likely correlates with individual training trajectories, and the paper's own limitations section acknowledges the imputation and the finalist-only sample. The contribution is of moderate significance for sports analytics rather than a methodological advance.

major comments (3)
  1. [Section 3.1 (M3 specification)] The text states that the random effects 'allow us to consider variations in both the initial skill level and the rate of progression of individual climbers.' However, the model as written in Section 3.1 includes random intercepts (μ0i, υ0j) and random slopes for TS usage (μ1i, υ1j) only; there is no random slope for the time progression variable x4i. The fixed coefficient γ04 is common to all climbers. Because adoption of the Tomoa Skip was voluntary and concentrated among elite, Olympic-focused athletes who were concurrently intensifying speed training, adoption timing is plausibly correlated with unobserved athlete-level improvement slopes. Under this scenario, γ01 will absorb part of the adopters' personal improvement, biasing the estimate away from zero. I consider a refit of M3 with climber-specific time slopes (e.g., a random slope for x4i, or a within-climber time trend) to be the decisive robustness check; the authors should report how γ01 and its CI change.
  2. [Section 2 / Section 4 (TS assignment and sample selection)] The paper acknowledges that TS usage is only observed for final-round broadcasts and imputes usage to unobserved rounds via the persistence assumption. This creates two threats to the main estimate. First, if climbers switch per round or per event without being observed (the paper documents one switch back), the predictor x1ij is misclassified; the direction of the resulting bias is not established. Second, restricting TS labels to finalists conditions the sample on reaching finals, so the estimate may not generalize to the broader population of speed climbers and may be subject to selection bias. The paper should add a sensitivity analysis, for example, estimating the model only on observations where TS use is directly video-confirmed, or treating unobserved rounds as missing rather than imputed.
  3. [Table 3 (fixed effects)] The units of the age and time progression variables are not clearly defined in the model output. The text says time progression x4i is 'the number of days since the first observed competition,' but the reported estimate γ04 = 0.0057 would then imply that each additional day increases log best time by 0.0057 (about 0.57% per day), which is implausibly large and inconsistent with the record-breaking trend described in Section 4. Similarly, γ03 = -0.0931 for age in years would imply about 9% faster times per additional year of age, which is also implausible over adult athletes' careers. The authors should state the scaling (e.g., days, years, or standardized values) and, if the variables are not on their natural scales, explain. This clarification matters for interpreting the fixed effects and for assessing whether the model is correctly specified.
minor comments (4)
  1. [Section 3.2] The first paragraph refers to 'the model used to analyze the effect of the Tomoa Skip on speed climbing times in Section 3.2'; this should be Section 3.1.
  2. [Figure 5] The axis label 'Worst - Best Times (s)' appears to be reversed relative to the text, which defines the range as 'best time minus their worst time'; please clarify the intended direction.
  3. [Table 3] The random effect correlations η01 and τ01 are -0.98 and -0.99, respectively; such near-perfect correlations can indicate non-identifiability or overparameterization and deserve a brief comment.
  4. [Section 3.1] The sentence 'In the world of speed climbing, where a fraction of a second can mean the difference between success and failure, this seemingly small improvement constitutes a significant and impactful advancement' could be strengthened by quantifying the effect relative to within-climber variability or the historical rate of record progression.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the Tomoa Skip effect is an estimated regression coefficient from independent outcome and predictor data, not a derived quantity built from its own target.

full rationale

The paper's central claim is an empirical association estimated by a mixed-effects regression: log best time is regressed on Tomoa Skip usage, gender, age, time progression, and random climber/event intercepts and slopes. The Tomoa Skip coefficient γ01 is fitted by maximum likelihood to observed IFSC results and manually coded video labels; it is not constructed from the outcome, nor is any parameter calibrated to the target estimate and then renamed as a prediction. There are no load-bearing self-citations, no imported uniqueness theorems, no ansatz smuggled in via citation, and no known empirical pattern merely renamed. The persistence assumption used to impute Tomoa Skip usage for unobserved rounds and the absence of climber-specific time trends are potential validity threats, but they are omitted-variable or measurement concerns, not circular reasoning. The derivation chain is therefore self-contained as a statistical analysis: the conclusion follows from the fitted model and data, not from an input that already contains the conclusion.

Assumptions & free parameters 0 free parameters · 3 assumptions · 0 invented entities

The central claim rests on the observational data, the persistence assumption for Tomoa Skip usage, and the standard mixed-effects modeling assumptions. No invented entities are introduced, and no hand-picked constants are used as inputs; all coefficients are estimated from the data.

assumptions (3)
  • domain assumption A climber who is observed using the Tomoa Skip in one round will continue using it in future rounds and competitions unless a later observation shows a switch.
    Section 2: the IFSC broadcasts only finals, so the authors propagate observed final-round usage to other rounds and subsequent events; they note this is an assumption and that only one switch back was observed.
  • domain assumption Tomoa Skip usage in the final round matches usage in the qualifying rounds of the same competition.
    Section 2: the outcome is the best time from any round, but the skip indicator comes from final-round video; if a climber used the skip only in the final, qualifying-only best times would be mislabeled.
  • domain assumption The log-linear mixed model with normally distributed random effects and independent climber errors is correctly specified for best times.
    Section 3.1: the model assumes log-linearity, normality of random effects, and independence across climbers; these are standard but unverified here.

how reviews work

0 comments
Cite this review

Pith. "Pith review of The Fast and the Furious: Tracking the Effect of the Tomoa Skip on Speed Climbing." pith.science (2026). https://pith.science/paper/O5ITBQ7T

@misc{pith2026241113696,
  author       = {Pith},
  title        = {Pith review of: The Fast and the Furious: Tracking the Effect of the Tomoa Skip on Speed Climbing},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/O5ITBQ7T}},
  note         = {Machine review of arXiv:2411.13696}
}
read the original abstract

Sport climbing is an athletic discipline comprised of three sub-disciplines -- lead climbing, bouldering, and speed climbing. These three sub-disciplines have distinct goals, resulting in specialization of athletes into one of the three events. The year 2020 marked the first inclusion of sport climbing in the Olympic Games. While this decision was met with excitement from the climbing community, it was not without controversy. The International Olympic Committee had allocated one set of medals for the entire sport, necessitating the combination of sub-disciplines into one competition. As a result, athletes who specialized in lead and bouldering were forced to train and compete in speed for the first time in their careers. One such athlete was Tomoa Narasaki, a World Champion boulderer, who introduced a new method of approaching the speed event. This approach, deemed the Tomoa Skip (TS), was subsequently adopted by many of the top speed climbers. Concurrently, speed records fell rapidly (from 5.48s in 2017 to 4.90s in 2023). Speed climbing involves ascending a 15m wall containing the same pattern of obstacles. Thus, records can be compared across time. In this paper we investigate the effect of the TS on speed climbing by answering two questions: (1) Did the TS result in a decrease in speed times? and (2) Do climbers who utilize the TS show less consistency? The success of the TS highlights the potential of collaboration between different disciplines of sport, showing athletes of diverse backgrounds may contribute to the evolution of competition.

Figures

Figures reproduced from arXiv: 2411.13696 by the authors.

Figure 1
Figure 1. (LEFT) The speed wall layout with hand holds labeled in order. (RIGHT) A zoom in on the first [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Demonstration of the initial sequence of the speed route by the author. The Tomoa Skip comprises [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. (LEFT) Number of events per year. There is an average of approximately 15 events per year, [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figures from the paper (3 more)
Figure 4
Figure 4. Figure 4: Progression of four climbers speed climbing times before and after adopting the Tomoa Skip. The [PITH_FULL_IMAGE:figures/full_fig_p011_4.png]
Figure 5
Figure 5. Figure 5: Boxplots of the ranges of climbers who use the Tomoa Skip vs those who do not. When the Tomoa [PITH_FULL_IMAGE:figures/full_fig_p012_5.png]
Figure 6
Figure 6. Figure 6: World record holdage over time. The grey rectangle denotes the period at which the Tomoa Skip [PITH_FULL_IMAGE:figures/full_fig_p014_6.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

9 extracted references · 9 canonical work pages

  1. [1]

    3.1 Effect of the Tomoa Skip on Speed Times In order to determine whether the Tomoa Skip has significantly impacted speed climbing times, we made use of mixed effects models

    3 How Important is the Tomoa Skip? We now turn to answering the question of the importance of the Tomoa Skip on speed climbing. 3.1 Effect of the Tomoa Skip on Speed Times In order to determine whether the Tomoa Skip has significantly impacted speed climbing times, we made use of mixed effects models. Mixed models have an extensive history of being applie...

    work page arXiv

  2. [2]

    Are climbers who use the Tomoa Skip faster?

    Figure 2: Demonstration of the initial sequence of the speed route by the author. The Tomoa Skip comprises moves 5-8 in the sequence of figures. The hold that is being skipped is circled in red. The introduction of the Tomoa Skip marked a shift in the speed climbing community. The fusion of bouldering and speed climbing techniques sparked by the upcoming ...

    work page 1990

  3. [3]

    This can be attributed to the disruptive impact of COVID, as global lockdowns significantly impeded the ability of athletes to participate and compete in climbing competitions

    Notably, in the year 2020, this pattern deviates, with only five competitions held. This can be attributed to the disruptive impact of COVID, as global lockdowns significantly impeded the ability of athletes to participate and compete in climbing competitions. In addition to this, we found that the speed climbing community quickly embraced the Tomoa Skip ...

    work page 2020

  4. [5]

    By 2022, the Tomoa Skip had become the predominant choice among professional speed climbers, and by the end of that 6 year, there are few climbers remaining who do not use the skip (see the right side of Figure 3 for reference). Table 1: Fall and False Start Rates in Final Rounds for Men and Women Category Events Falls False Starts Fall Rate False Start R...

    work page 2022

  5. [6]

    While interesting, our findings were somewhat limited by the data that was available. The absence of formally documented data on who has performed the Tomoa Skip limits our data to what we can view in recorded competitions, limiting our knowledge to climbers who have reached final rounds. This could potentially bias our findings towards those top speed cl...

    work page 2020

  6. [7]

    We observe an estimated fixed effect for the Tomoa Skip of -0.1568 with corresponding 95% CI of (-0.1898, -0.1238). Because we took the logarithm of the climbers’ best times in each event, this estimate signifies that after controlling for variation in individual climbers and events, using the Tomoa Skip is associated with an approximately 0.8549 times de...

    work page 2000

  7. [8]

    The range for an individual climber in an event is specified by their best time minus their worst time for that event. A climber with a low range can be said to be highly 11 Jakarta (INA) 2022 Edinburgh (GBR) 2022 Chamonix (FRA) 2022 Villars (SUI) 2022 Salt Lake City (USA) 2022 II Salt Lake City (USA) 2022 I Seoul (KOR) 2022 Moscow 2021 Villars (SUI) 2021...

    work page 2022

  8. [2018]

    time progression

    In order to determine which climbers employed the Tomoa Skip, we slowed each video down to half speed or slower, giving us a more detailed view of each climber’s movements. For each climber competing in the video we were viewing, we watched for whether they executed the Tomoa Skip by identifying whether they used their feet on the first hold to propel the...

    work page 2020

Show all 9 references
  1. [2021]

    Having that muscle memory makes you go faster because hitting everything perfectly is one thing that takes off a fraction of a second

    What was once a pursuit of few has now become a pastime for millions, a unique blend of athleticism, mental-fortitude, and strategy unlike any other. Competitive climbing can be broken up into three main disciplines: lead climbing, bouldering, and speed climbing. Governed by t...

    2024 arXiv

Pith tools

Reviewed August 12, 2026 · model on record in the stance chip above.