Research Review: Physiological Predictors of Performance in Competitive Ski Mountaineering

By Rob Shaul

BLUF (Bottom Line Up Front) A 2021 study of 21 male Austrian SKIMO athletes (including National Team members) found that VO2max, velocity at VT2, and peak lactate levels were the strongest performance predictors in a simulated vertical race. The study also found that in a controled laboratory setting, the elite SKIMO athletes had longer skinning stride lengths, despite not being significantly taller.

Purpose of the Study

Measure physiological responses during a simulated vertical SKIMO race and compare them to a laboratory SKIMO-specific ramp test.
Identify performance predictors such as VO2max, power output, lactate levels, and step characteristics in elite vs. sub-elite SKIMO athletes.

Subjects
21 male SKIMO athletes divided into:

Elite group (n=8): Austrian National Team members or athletes with similar competitive results.
Sub-elite group (n=13): Competitive athletes but not at the elite level.

Anthropometric Data:

Height (m):

- Elite athletes: 1.84 ± 0.06 m (range: 1.71–1.91 m)
- Sub-elite athletes: 1.81 ± 0.06 m (range: 1.68–1.90 m)
- p = 0.335 (not statistically significant)

Body Mass (kg):

- Elite athletes: 72.6 ± 7.4 kg (range: 61.0–81.5 kg)
- Sub-elite athletes: 74.3 ± 8.7 kg (range: 53.0–84.0 kg)
- p = 0.645 (not statistically significant)

BMI (kg/m²):

- Elite athletes: 21.4 ± 1.3
- Sub-elite athletes: 22.6 ± 2.3
- p = 0.121 (not statistically significant)

Age:

- 31.3 ± 8.8 years overall, with no significant difference between elite (32.3 ± 9.5) and sub-elite (30.7 ± 8.7) groups.

Research Method:
Two sessions per athlete within two weeks. The athletes used their own race equipment for both tests:

First was a “Field Test” simulated Skimo race on a local ski slope in Obertaurern, Austria:

Elevation gain: 532 meters over 2,710 meters distance).
Altitude: Start at 1668 m, finish at 2200 m.
Conditions: Compact machine snow, fresh snow, and spring snow, with temperatures between -6°C and +7°C.

Second was a Laboratory Test inside where the subjects skinned on an inclined treadmill with a 24% constant grade:

Speed: Starting at 3.4 km/h, increasing by 0.4 km/h every minute until exhaustion.
Equipment: Cosmed K5 portable metabolic system, Wahoo Tickr HR belt, Pomocup inertial sensor for stride metrics.
Data Collected: VO2, HR, blood lactate, ventilation (VE), respiratory rate (RR), step length (SL), cadence (C).
Statistical Tools: SPSS (version 25), Shapiro-Wilk test, t-tests, Mann-Whitney U tests, Pearson’s correlation (p < 0.05 significance).

Findings:

Simulated Race Performance (Field Test):

Finish Times:

Elite athletes completed the course in 27:15 ± 1:16 min, while sub-elite athletes took 32:31 ± 2:13 min (p < 0.001), a 19% difference.
Walking Velocity: Elite – 6.0 ± 0.3 km/h vs. Sub-elite – 5.0 ± 0.3 km/h (p < 0.001).
Vertical Velocity: Elite – 1173 ± 56 m/h vs. Sub-elite – 985 ± 63 m/h (p < 0.001).

The elite SKIMO athletes were significantly faster. They finished the course about 5 minutes quicker than the sub-elite athletes, completing the race in roughly 27 minutes compared to 32.5 minutes. That’s a 19% faster finish time. Their walking speed was about 1 km/h faster, and they climbed vertically at a rate of 1173 meters per hour compared to 985 meters per hour for the sub-elite group (again, 19% faster). Essentially, the elite athletes covered more ground, uphill, much quicker while maintaining similar heart rates.

Heart Rate (HR):

Mean HR during race: Elite – 174 ± 11 bpm vs. Sub-elite – 176 ± 9 bpm (p=0.636).
Peak HR: Elite – 182 ± 14 bpm vs. Sub-elite – 184 ± 9 bpm (p=0.677).

The lack of significant difference in heart rate (HR) between elite and sub-elite SKIMO athletes suggests that both groups experienced similar cardiovascular strain during the race. However, elite athletes achieved superior performance (faster finish times, higher VO2) despite similar HR levels, indicating that they were more efficient in oxygen utilization and energy production. This efficiency allows elite athletes to maintain higher speeds and greater workloads without an increase in cardiovascular strain compared to their sub-elite counterparts.

Oxygen Uptake (VO2):

VO2mean during race: Elite – 58.9 ± 8.4 ml·min⁻¹·kg⁻¹ vs. Sub-elite – 51.3 ± 7.5 ml·min⁻¹·kg⁻¹ (p=0.046).
VO2peak during race: Elite – 67.8 ± 10.3 ml·min⁻¹·kg⁻¹ vs. Sub-elite – 59.6 ± 6.6 ml·min⁻¹·kg⁻¹ (p=0.040)

During the field test, VO2mean and VO2peak were measured using a portable metabolic system (Cosmed K5) worn by athletes. This device continuously monitored their oxygen consumption throughout the race, calculating the average VO2 (VO2mean) over the entire effort and the highest oxygen uptake recorded at any point during the race (VO2peak). This method allowed real-time collection of respiratory data under race conditions, which was then compared to lab-measured VO2max to assess how close athletes performed to their maximum capacity. Comparing these to lab-measured VO2max indicates how close each athlete performed to their maximum capacity during the race.Elite athletes had a higher VO2mean and VO2peak during the field test, indicating they performed closer to their VO2max measured in the lab. This reflects superior aerobic efficiency, allowing elite athletes to maintain intense effort longer, delay fatigue, and recover faster. Sub-elite athletes, despite similar heart rates, could not utilize oxygen as efficiently, limiting their endurance and speed during the race.This efficiency ensures better energy production, faster recovery during brief rests, and improved endurance, particularly during uphill climbs where aerobic metabolism is essential. Higher VO2 means elite athletes can deliver more oxygen to working muscles, delaying fatigue and enhancing performance compared to sub-elite athletes who may fatigue faster at similar intensities.

Ventilation (VE):

VEmean during race: Elite – 149 ± 21 l/min vs. Sub-elite – 129 ± 20 l/min (p=0.049).

The elite SKIMO athletes had a higher ventilation rate (149 L/min) compared to sub-elite athletes (129 L/min), indicating they breathed more air per minute during the race. This suggests better respiratory efficiency and a greater capacity to meet oxygen demands at high intensity. Despite similar heart rates, elite athletes maintained higher airflow, allowing for better oxygen delivery to muscles, which likely contributed to their superior performance.

Lactate:

Post-race lactate at 5 minutes: ~20% higher in elite athletes (p=0.044).
Post-race lactate at 10 minutes: ~20% higher in elite athletes (p=0.049).

Higher post-race lactate in elite athletes indicates they pushed closer to their physiological limits during the race. Lactate is produced when the body relies on anaerobic metabolism due to high intensity. Elite SKIMO athletes’ higher lactate levels suggest greater metabolic strain and capacity to sustain high effort longer. It reflects their ability to buffer and tolerate lactate accumulation better than sub-elite athletes, enabling them to maintain faster speeds despite the fatigue-inducing effects of lactate buildup.

Laboratory Results:

VO2max:

Elite – 71.2 ± 6.8 ml·min⁻¹·kg⁻¹ vs. Sub-elite – 62.5 ± 4.7 ml·min⁻¹·kg⁻¹ (p=0.003).

The elite athletes’ VO2max (71.2 ml·min⁻¹·kg⁻¹) was significantly higher than the sub-elite group (62.5 ml·min⁻¹·kg⁻¹), indicating superior aerobic capacity. This difference of about 14% means elite athletes can utilize more oxygen during intense effort, enhancing endurance and efficiency, especially during prolonged uphill climbs in SKIMO races.

The observed difference in VO₂max between elite (71.2 ± 6.8 ml·min⁻¹·kg⁻¹) and sub-elite athletes (62.5 ± 4.7 ml·min⁻¹·kg⁻¹) can be attributed to both genetic and environmental factors. Studies suggest that genetics account for approximately 50% of an individual’s VO₂max capacity. This indicates that while genetic predisposition plays a significant role, training and environmental influences are equally crucial in determining VO₂max levels. Therefore, the higher VO₂max observed in elite athletes is likely due to a combination of favorable genetics and rigorous training regimens.

Velocity at VT2:

Elite – 6.3 ± 0.6 km/h vs. Sub-elite – 5.5 ± 0.4 km/h (p=0.008).

VT2 (second ventilatory threshold) is the exercise intensity where lactate accumulates faster than the body can clear it, marking the shift to anaerobic metabolism. In this study, elite SKIMO athletes had a higher velocity at VT2 (6.3 km/h vs. 5.5 km/h), meaning they could sustain faster speeds before reaching this limit. This advantage allows elite athletes to maintain high performance longer without fatigue, a critical factor in endurance events like ski mountaineering.

Maximum Velocity (Vmax):

Elite – 7.4 ± 0.3 km/h vs. Sub-elite – 6.6 ± 0.3 km/h (p < 0.001).

The elite SKIMO athletes’ maximum velocity in the lab test was 12.1% higher than sub-elite athletes (7.4 km/h vs. 6.6 km/h). This significant difference highlights their superior power output, aerobic capacity, and technical efficiency, allowing them to sustain faster speeds at peak effort—critical for high-performance ski mountaineering, particularly during steep ascents and prolonged races.

Step Length (SL):

SLmean in lab: Elite – 0.83 ± 0.06 m vs. Sub-elite – 0.75 ± 0.07 m (p=0.035).
SLmax in lab: Elite – 0.94 ± 0.06 m vs. Sub-elite – 0.87 ± 0.07 m (p=0.046).

Elite SKIMO athletes had a mean step length of 0.83 meters compared to 0.75 meters for sub-elite athletes (p=0.035), with maximum step lengths of 0.94 meters vs. 0.87 meters (p=0.046). Despite this, there was no significant difference in height between the groups (elite: 1.84m; sub-elite: 1.81m), suggesting that height did not contribute to the longer strides. The difference is likely due to superior strength, technique, and efficiency in elite athletes, allowing them to cover more ground with each step and maintain faster speeds during SKIMO races.

Performance Predictors:

Key Predictors Identified by Multiple Regression:

– Maximum velocity (vmax) from the lab test.
– VO2peak during the field test.
– Lactate peak in % of max during the race.

These three explained 84% of performance variation (r²=0.84, p<0.001).

Correlations:

Race time correlated negatively with VO2peak (r=-0.700, p<0.001), vmax (r=-0.783, p<0.001), and lactate peak in % max (r=-0.474, p=0.035).

Equipment Differences

Athletes used their own race equipment, but differences were not explicitly measured in the study.

Conclusions

Elite SKIMO athletes exhibit significantly higher VO2max, ventilation rates, and maximum velocities.
VO2peak, vmax, and lactate tolerance are essential for SKIMO success.
Training should emphasize enhancing VO2max, power output at VT2, and stride efficiency.
Portable metabolic systems provide valuable field data, suggesting that sport-specific performance diagnostics are vital for athlete development.

Genetics …. And the VO₂max advantage of the Elite athletes ….

Research has found that genetics account for approximately 50% of VO₂max, we can estimate how much of the performance difference between elite and sub-elite athletes is due to genetic factors.

Step-by-Step Estimation:

VO₂max Difference:

Elite: 71.2 ml·min⁻¹·kg⁻¹
Sub-elite: 62.5 ml·min⁻¹·kg⁻¹
Difference: 8.7 ml·min⁻¹·kg⁻¹

Genetic Contribution (50% of VO₂max):

50% of 8.7 = 4.35 ml·min⁻¹·kg⁻¹ due to genetics.

Adjusted VO₂max for Sub-Elite Without Genetic Disadvantage:

62.5 + 4.35 = 66.85 ml·min⁻¹·kg⁻¹

This is still lower than the elite average (71.2 ml·min⁻¹·kg⁻¹), but much closer.

Predicting Finish Time Impact:

Since VO₂max, vmax, and VO₂peak were key predictors of performance, we assume that improving VO₂max by ~7% (from 62.5 to 66.85) would similarly improve sub-elite finish times.

•Elite finish time: 27:15 min
•Sub-elite finish time: 32:31 min (19% slower)
A 7% improvement in VO₂max could lead to approximately a 7% improvement in finish time:
•7% of 32:31 is about 2:16 minutes.
•Predicted sub-elite finish time without the genetic disadvantage: ~30:15 min.

This suggests that, without the genetic disadvantage in VO₂max, sub-elite athletes could have reduced their finish times by roughly 2-2.5 minutes, though they would still likely finish behind elite athletes due to other factors such as training, experience, and technical skill.

Training Implications of the Study’s Findings:

Focus on VO2max Development: Since VO2max was a major determinant of performance, athletes should incorporate high-intensity interval training (HIIT), long-duration aerobic sessions, and altitude training to maximize oxygen uptake.
Enhance Power at VT2: Training should include threshold workouts just below or at VT2, improving the ability to sustain high effort without accumulating excessive lactate.
Increase Lactate Tolerance: Anaerobic training such as short sprints and repeated high-intensity efforts can help athletes improve lactate buffering and maintain performance under fatigue.
Optimize Stride Length and Efficiency: Technical drills, uphill running, and strength training for the lower body will improve step length, reducing energy cost and enhancing speed.
Respiratory Training: Given elite athletes’ higher ventilation rates, breathing exercises and respiratory muscle training can enhance ventilation efficiency.
Monitoring and Testing: Regular VO2max and ventilatory threshold testing will help track progress and adjust training loads accordingly.
Holistic Approach: While genetics play a role, structured training focusing on aerobic capacity, strength, and technique can help bridge the performance gap.

Source: Lasshofer, M., Seifert, J., Wörndle, A.-M., & Stöggl, T. (2021). Physiological Responses and Predictors of Performance in a Simulated Competitive Ski Mountaineering Race. Journal of Sports Science and Medicine, 20, 250-257.

DOI: 10.52082/jssm.2021.250

Link to full text: Journal of Sports Science and Medicine