How much faster is skimo race gear?

Inspired by a Reddit post, I tested different-weight ski setups on the same terrain and conditions to measure the impact of weight on climb rate. To isolate weight as the only variable, I completed four laps at a controlled intensity:

1. with race gear;
2. with light touring;
3. with typical touring; and
4. again with race.

The Test

• To ensure precision, I used a chest strap heart rate monitor rather than an optical wrist sensor. A chest strap directly measures heart rate via electrical activity, while a wrist monitor does so indirectly, measuring blood flow;
• To ensure a repeatable intensity, I targeted my aerobic threshold rather than my anaerobic. Since the aerobic threshold can be maintained for hours, there's less chance of fatigue affecting the result;
• To compare different weights, I used three sets of ski equipment:
  • Race: 1,526 grams per side, including skins, skis, bindings, boots, and poles;
  • Light Touring: 2,602 grams per side; and
  • Typical Touring: 3,286 grams per side.
• To minimize errors, I did four laps rather than three. This served two purposes:
  • To test the RPE of the first lap: The first lap was a warm-up, so although my pace was constant, it took close to 15 minutes for my heart rate to reach my aerobic threshold.¹ Heart rate always lags intensity, so I used a steady pace and waited for my heart rate to catch up.² The fourth ascent was only 0.6% slower than the first—16:46 vs. 16:38—so I could confirm that my starting pace was correct.
  • To test if fatigue was a factor: Although the laps were short, I wanted to ensure that any increase in time was not due to fatigue and a slowing pace. By bookending the session with laps on the same equipment, I could compare the times and adjust if necessary. (However, with only a 0.6% time difference, an adjustment isn't required; the errors in GPS and VAM calculations are probably more significant.)

Equipment Weight

Here are the weights per component and the increases (in grams and percentages) compared to the Race equipment.

Compared to the Race equipment, Light Touring was 70.5% heavier, and Typical Touring was 115%.

Lap Times

Compared to the Race laps, Light Touring was 14.3% slower; Typical Touring, 20%.

Conclusions

Gear weight significantly affects uphill efficiency.

Adding just over a kilogram (per side) decreased the climb rate by 14% between the Race setup and Light Touring.

For the full impact, the total system weight must be compared.

It's misleading to consider only the equipment. The weight increase between Race and Light Touring was 70%. In isolation, that suggests a significant change is needed to affect the climb rate, but the actual tipping point is much lower.

In contrast, the increase in weight compared to the total system weight—gear plus clothing plus body weight—is proportionally slight. In this case, it was only 2.87%.

\(\text{Weight Increase} = \frac{77,204 - 75,052}{75,052} \times 100 = \frac{2,152}{75,052} \times 100 = 2.87\%\)

Every 1% increase in total system weight resulted in a 5% decrease in ascent speed.

Only when total body weight is included can we calculate the actual impact.

System weights for a 70 kg skier:

\(\text{Total System Weight} = \text{body weight} + \text{clothing} + \text{equipment}\)

\(\text{Total System Weight (Race)} = 70,000 + 2,000 + 2(1,526) = 75,052 \text{ g}\)

\(\text{Total System Weight (Light Touring)} = 70,000 + 2,000 + 2(2,602) = 77,204 \text{ g}\)

Percentage increase in weight:

\(\text{Weight Increase} = \frac{77,204 - 75,052}{75,052} \times 100 = \frac{2,152}{75,052} \times 100 = 2.87\%\)

Time penalty per 1% weight increase:

\(\frac{\text{Time Increase (\%)}}{\text{Weight Increase (\%)}} = \frac{14.3}{2.87} = 4.99\)

🤓 Math FTW!

Lighter equipment has a bigger impact on smaller people.

Increasing equipment weight by 1 kg is a 1% increase (and likely a 5% slowdown) for a 100 kg person. But for a 70 kg person, 1 kg is a 1.43% increase (likely a 7.1% slowdown).⁴

Transitions with Race gear are no contest.

Although the times were decent, considering the awkwardness of the equipment, the touring transitions were still three times slower.

Better skis don't make for faster descents.

I didn't descend at race pace, but at roughly the same feel. The top speeds of Race and Light Touring were pretty much the same—74.4 km/h versus 75.0—despite having much more confidence in the edge grip of the Light Touring setup.

What wasn't tested

Is there a minimum weight that triggers the slowdown?

It appears not. Weight increases as low as 100 grams have an effect.

How Much Do Heavy Shoes Slow You Down?

A study finds that adding even a few ounces affects race times.

Runner's Worldalex hutchinson

Does the location of the weight matter?

Yes. The general rule of thumb is that increased weight on the feet is equivalent to five times that on your back—similar to what I found with my quick-and-dirty test.

Study: Energy cost of backpacking in heavy boots,

How does duration change the effect?

I suspect longer durations make the slowdown worse. It's well-known that high-cadence, low-load movement patterns are more aerobic than low-cadence, high-load patterns.

Increased weight increases the muscular load, increasing the demand for fast-twitch muscle fiber. A fast-twitch muscle fiber is more glycolytic, burning carbohydrates faster.

A heavier load not only reduces speed but also decreases fuel efficiency.

If you consume more carbohydrates per unit of effort, your glycogen reserves will deplete faster. This will result in an earlier onset of fatigue and, in the worst case, bonking sooner.

Pounds make pain.

Ounces make pounds, and pounds make pain.

The inverse is also true: removing weight creates joy.

It felt horrible when I switched from Race to Light Touring and then worse again to Typical Touring. But from Typical Touring to Race, it was a thrill.

The opposite sentiment? "Go light, delight!"

1. To force a specific heart rate in too short a time is "wagging the dog". Because of heart rate lag, the initial speed would be too high, and heart rate would misrepresent the intensity. In this case, that extra speed would have overstated the importance of lightweight equipment.
2. When training, I always note my ventilation patterns relative to my heart rate. With that experience, I can maintain specific intensities by monitoring ventilation for different durations. For uphill hiking and skinning, breathing with a two-steps-in, two-steps-out rhythm for 15+ minutes will be about aerobic threshold. (In contrast, two-in, two-out at the start of a race is closer to anaerobic threshold because it can only be held for ~5 minutes.)
3. I had to interrupt these descents in the interest of skier-snowcat diplomacy. In between runs, a snowcat started work on part of my descent, so I had to slow down and detour. Interestingly, the top speed of the second Race run was still close to that of Light Touring.
4. Going alpine climbing? This demonstrates why evenly distributing weight between packs is inefficient—it slows smaller team members more than larger ones. For the highest team speed, pack weight should be scaled according to the person's weight. (My climbing partners who outweigh me by 50 pounds always balk at this idea...)

How to use "The 1% Rule"