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Outdoor Research Alpine Onset Bottoms Review

A versatile, lightweight merino-recycled polyester blend that offers superb breathability and wicking, making these a near ideal high performance bottom for any fast-paced adventure
Outdoor Research Alpine Onset Bottoms
Credit: Outdoor Research
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Price:  $89 List | $88.95 at Amazon
Pros:  Breathable, highly efficient wicking, comfortable merino/recycled polyester blend, impressively durable
Cons:  Not designed for mid-winter warmth, relatively heavy for fabric weight, thin waist band
Manufacturer:   Outdoor Research
By Aaron Rice ⋅ Review Editor  ⋅  Nov 4, 2021
Our Editors independently research, test, and rate the best products. We only make money if you purchase a product through our links, and we never accept free products from manufacturers. Learn more
73
OVERALL
SCORE


RANKED
#3 of 11
  • Warmth - 30% 6.0
  • Breathability - 30% 9.0
  • Comfort and Fit - 30% 7.0
  • Durability - 10% 7.0

Our Verdict

Back by popular demand, Outdoor Research has revived and revamped the Alpine Onset Merino bottoms, and we couldn’t be happier about that fact. A previous award-winner, this updated version has impressed us once again with its ability to balance breathability with just the right amount of warmth to offer up a nearly ideal lightweight base layer. This pair of merino-blended bottoms is composed of nearly half recycled polyester, and incorporates just a touch of elastane jersey material for added strength and softness. Not necessarily our choice for the depths of mid-winter, the Alpine Onset excels as a versatile layer across all four seasons, but especially in spring and fall. From multi-day backpacking trips to chilly alpine starts, these bottoms are sure to become a go-to for any athletic adventure.

Compare to Similar Products

 
Awards  Editors' Choice Award Top Pick Award Best Buy Award Best Buy Award 
Price $89 List
$88.95 at Amazon
$110 List$110 List
$110.00 at REI
$50 List
$24.83 at REI
$40 List
$39.95 at REI
Overall Score Sort Icon
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Pros Breathable, highly efficient wicking, comfortable merino/recycled polyester blend, impressively durableSoft next-to-skin, super warm for its weight, durable and all-naturalExtremely breathable, ultralight stretchy nylon/Merino wool blendGreat value, warm but still breathable, very comfortable for a syntheticUnbeatable price, breathable, quick drying, functional
Cons Not designed for mid-winter warmth, relatively heavy for fabric weight, thin waist bandA touch heavy for fabric weight, slow to dry after washingPrice may make you do a double-take, care instructions need to be followed when dryingSlightly short inseam, fabric could be stretchierShort cut legs, average comfort and warmth
Bottom Line A versatile, lightweight merino-recycled polyester blend that offers superb breathability and wicking, making these a near ideal high performance bottom for any fast-paced adventureUndeniably comfortable, warm, and breathable, this rough-and-tumble pair of 100% merino long underwear has it allA seriously tuned ultralight pair of wool/nylon blend leggings built for fast and light outdoor adventuresFor cold weather trips on a budget, this pair of synthetics are hard to beatSlender and breathable, these are everything we expect out of a lightweight pair of long underwear
Rating Categories Outdoor Research Al... Ortovox 185 Rock'N'... Artilect Boulder 125 REI Co-op Midweight... REI Co-op Lightweig...
Warmth (30%)
6.0
8.0
6.0
8.0
5.0
Breathability (30%)
9.0
7.0
9.0
6.0
8.0
Comfort and Fit (30%)
7.0
8.0
8.0
7.0
6.0
Durability (10%)
7.0
7.0
6.0
8.0
6.0
Specs Outdoor Research Al... Ortovox 185 Rock'N'... Artilect Boulder 125 REI Co-op Midweight... REI Co-op Lightweig...
Material 47% Merino wool, 47% recycled polyester, 6% spandex 100% Merino wool 85% Nuyarn Merino wool, 15% nylon 100% polyester 92% polyester, 8% spandex
Fabric Weight 150 g/m² 185 g/m² 125 g/m² N/A N/A
Weight (size M) 6.8 oz 6.4 oz 4.34 oz 7.62 oz 5.46 oz
Insulation Weight Lightweight Midweight Lightweight Midweight Lightweight
3/4 Boot-Cut Available? No Yes Yes No No
Fly? Yes No No Yes Yes
Dryer safe? No No No Yes Yes

Our Analysis and Test Results

The Outdoor Research Alpine Onset Merino Bottoms receive a material upgrade from the previous model. Though still a merino-blend, the design team at Outdoor Research swapped nylon fibers for Repreve recycled polyester for improved moisture wicking. They also swapped spandex for elastane jersey, making these blended bottoms even softer next-to-skin. The result is a 47% merino wool, 47% recycled polyester, 6% elastane jersey construction — an ultimate blend for comfort and performance.

Performance Comparison


Outdoor Research Alpine Onset Bottoms long underwear - you wouldn't know it by this photo, but our morning on this alpine...
You wouldn't know it by this photo, but our morning on this alpine route high above the Rio Grande valley started in the rain and snow! The OR Alpine Onset bottoms were the perfect companion, keeping us warm enough in the early morning and breathing well through our long afternoon descent.
Credit: Jill Rice

Warmth


As far as lightweight bottoms go, we hardly expect these pairs of long underwear to compete in the warmth category against heavier-weight fabrics. While weight and warmth walk practically hand-in-hand when it comes to all-natural layers (i.e., 100% merino), you cannot fairly assume that a blended bottom won’t outperform its weight class when it comes to keeping you warm and cozy. Although the Alpine Onset bottoms aren’t designed for standing around an ice climbing belay, these lightweight bottoms exceeded our initial expectations for warmth.

A stealthy blend of merino wool, recycled polyester, and elastane jersey, the Alpine Onset bottoms are listed as having a fabric weight of 150 g/m², landing them firmly on the lightweight end of the spectrum when it comes to the average base layer fabric weights. So it surprised us when they tipped the scales at 6.8 ounces (for a size medium), weighing in on point with other pairs with fabric weights closer to 200 g/m². And indeed, these thin, lightweight bottoms effectively trap warm air better than expected. Layered underneath a pair of rock pants, they offer just enough warmth to cut the chill of an early-morning approach. But their ability to effectively thermoregulate truly lies in their ability to breathe.

Outdoor Research Alpine Onset Bottoms long underwear - ski patrolling is hard work. these layers will keep you dry, warm...
Ski patrolling is hard work. These layers will keep you dry, warm, and comfortable as you pull ropes and move toboggans (but you may want a hut to warm up in between runs!)
Credit: Jill Rice

Breathability


What these bottoms (slightly) lack in terms of warmth, they all but make up for in terms of breathability. Their light fabric weight allows for efficient airflow — like the Goldilocks zone, we never found ourselves too cold or too hot while wearing these bottoms. Utilizing the natural powers of merino wool, the Alpine Onset bottoms' ability to thermoregulate is what allows this pair of long underwear to perform so well as a multi-season layer. As you begin to work up a sweat, the merino fibers quickly wick that moisture away from your skin, efficiently passing it from the interior to the exterior of the fabric.

Even though merino is super in its own right, pairing this all-natural wonder-fiber with recycled polyester gives any base layer superpowers. Although merino wool is naturally hydrophobic, any material that is used for its wicking properties runs the risk of becoming oversaturated — once soaked, merino wool takes quite a long time to dry out. That’s where the recycled polyester comes into play, stepping up as a fast-drying fabric to offer its hand in superior moisture management. The result is an efficient-wicking, fast-drying fabric combination that quickly evaporates away moisture and allows these bottoms to breathe. Even on an all-day alpine climb in the desert Southwest — where the early-morning rain gave way to sun and 60-degree temperatures — we continued to be comfortable in the breathable Alpine Onset bottoms, even on an hours-long descent back to the trailhead.

Outdoor Research Alpine Onset Bottoms long underwear - cool weather, fall trail runs are the perfect testing ground for...
Cool weather, fall trail runs are the perfect testing ground for lightweight bottoms. The secret to the impressive breathability of the Alpine Onset is the combination of merino wool and recycled polyester to efficiently wick up, and then evaporate away sweat and moisture build-up.
Credit: Jill Rice

Comfort and Fit


Breathability and comfort are truly what make the Alpine Onset bottoms such a versatile, four-season layer. While the merino wool and recycled polyester work flawlessly as a team to keep you dry and comfortable — no matter how hard you’re pushing uphill — the 6% elastane jersey is included to help bump the numbers in terms of next-to-skin comfort. While elastane is a catch-all fabric term that includes spandex, jersey knit is a technique that loops one continuous piece of yarn over itself. Imagine, for a moment, the suppleness of jersey sheets… while spandex is singularly stretchy, elastane jersey is both stretchy and incredibly soft next-to-skin.

While previous versions were defined by a next-to-skin type of fit — think thigh-hugging leggings — the re-designed Alpine Onset bottoms offer a much more forgiving cut, making them more approachable for all body shapes and sizes. For this update, the design team at OR ditched the “seamless” construction, in favor of a more classic tri-panel design, with a gusseted crotch and functional fly.

Outdoor Research Alpine Onset Bottoms long underwear - fit of the alpine onset bottoms: a tapered cut, offering more room...
Fit of the Alpine Onset bottoms: a tapered cut, offering more room in the thighs and seat, while the shins and ankles are held snuggly by separate articulated panels. Our tester is 5'10", 160lbs wearing a size Medium.
Credit: Jill Rice


But in terms of fit, these are a far cry from a traditional pair of long underwear. Simple in appearance, but outstanding in terms of function, our favorite design point is the inclusion of two additional panels around the shins and ankles. This allows the leg to taper to a snug ankle cuff — keeping the bottoms from bunching up onto your calf — while at the same time affording more room and mobility through the thighs and knees.

Outdoor Research Alpine Onset Bottoms long underwear - a close-up view of the individual panels that taper to a more slim...
A close-up view of the individual panels that taper to a more slim fit around your shins and ankles. This ensures that these bottoms stay in place, regardless of how your moving in them.
Credit: Jill Rice

Durability


Like other 150 g/m² fabric weight options, these bottoms feel almost too thin to be very dependable. Savvy consumers will notice that similar weight models — both 100% merino and full-synthetic — fall short of our durability demands. While we certainly hold products to a high standard, we firmly believe that products built with higher quality construction are ultimately more valuable. Fortunately for all involved, the Alpine Onset bottoms once again harness the capability of hybrid fabrics, and their performance extends to a level of durability altogether unexpected from this lightweight powerhouse.

Our laboratory abrasion test is designed to recreate the standard Martindale abrasion test, and vigorous rubbing over sandstone is certainly a tough way to test base layers. Amazingly, the face fabric of the Alpine Onset bottoms was practically unphased — in fact, we later had a tough time even finding the exact spot where we performed our durability test. While the flat seam construction is made more robust by flatlock seams, interestingly the seams were the spot that took the most beating in our test. However, the inner seams remained completely intact, even after repeated wash cycles. While our testing period is limited, this is surely a good indication of a long life for this pair of long underwear, regardless of how you use them.

Outdoor Research Alpine Onset Bottoms long underwear - a close up after our abrasion test. while the spot on the face...
A close up after our abrasion test. While the spot on the face fabric is faint, we can see some wear-and-tear of the flatlock seams. Despite the dropped seams visible from the outside, the flip-side remains 100% intact.
Credit: Aaron Rice

Value


Even though these are a blended bottom, expect to pay close to 100% merino prices for this technically-advanced base layer. But the combination of performance, comfort, and durability that the Alpine Onset brings to the table all make a strong argument for the overall value of this versatile pair of lightweight long underwear. Especially for those who enjoy fast-and-light pursuits in the mountains — regardless of the season — these are a worthwhile addition to your gear closet.

Outdoor Research Alpine Onset Bottoms long underwear - the alpine onset kit is invaluable for lightweight backpacking. this...
The Alpine Onset kit is invaluable for lightweight backpacking. This pair of bottoms offers just enough warmth to keep you cozy through the night, and is breathable enough to comfortably walk miles in during those chilly days.
Credit: Jill Rice

Conclusion


The Outdoor Research Alpine Onset Merino Bottoms quickly became a fan-favorite among our testers. An uber-comfortable pair of long underwear that prioritizes breathability, but incorporates just the right touch of warmth. These bottoms are the perfect choice for the midwinter uphill athlete, as much as they are for the through-hiker looking for a versatile and lightweight base layer to carry them through their multi-season adventure.

Aaron Rice
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