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Under Armour Base 4.0 Review

Under Armour Base 4.0
Price:   $85 List | $63.74 at Backcountry
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Pros:  Very breathable, sufficiently durable, not too warm for high intensity sports
Cons:  Uncomfortable, cannot fit over another layer, no style
Bottom line:  The 4.0 is suited for traditional team sports in cold weather, but doesn't fit in with the rest of the crowd for most outdoor recreational activities.
Editors' Rating:     
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Manufacturer:   Under Armour
By Ross Robinson
Monday December 19, 2016

Our Verdict

Under Armour is considered by more than a few in the athletic world to be at the precipice of high-performance clothing. We have often been fond of this company's ability to make solid work-out clothes, as well as kits for traditional team sports. So, we were intrigued by the latest base layer, the Base 4.0, that Under Armour recently dropped on the market. This synthetic model proved to be supremely breathable, wicking away sweat and removing moisture almost as quickly as we could produce it. In other categories, though, this model was found to be considerably lacking, especially in comfort and fit, warmth, and layering ability.

There were a few other comparable synthetic models that performed better across the board than the Base 4.0. Our Best Buy award winner, The North Face Warm offers (surprise!) more warmth and a huge advantage in terms of comfort and layering ability. For another solid performer for rigorous activities, check out the Helly Hansen Lifa Stripe Crew, a thin and ultralight top that provides more comfort and higher performance in general.


RELATED REVIEW: The Best Long Underwear and Base Layer for Men

Our Analysis and Test Results

The Base 4.0 by Under Armour, priced at $85, is a synthetic form-fitting base layer best used in cold weather for traditional team sports, as opposed to outdoor recreational use. It is a very breathable top, dries fairly quickly, and appears to have acceptable durability. However, it scored very poorly in warmth, comfort and fit, and layering ability.

Performance Comparison


The tight-fitting product from Under Armour is more suited for the high intensity team sports than outdoor adventures.
The tight-fitting product from Under Armour is more suited for the high intensity team sports than outdoor adventures.

Warmth


Despite having a low fabric density of 172 g/m², the Base 4.0 still weighed nine and a half pounds. Weighing almost the same as the SmartWool Merino 250 Base Layer model, this product didn't provide nearly the warmth as its merino wool competitor. This is not necessarily a bad thing. For hotter temps or high-intensity workouts, a less insulating top may be called for, but don't expect this shirt to do too well in the Arctic.

This product does have a drop tail for a cozier booty, as well as thumb straps. However, like the rest of this top, the thumb loops were too tight to be comfortable, and therefore rarely used. Furthermore, this was the only model that is singularly available in a crew cut, with no zip neck or hooded options that could add more warmth.

Ross Robinson utilizing a three layer system while skiing in the Sierras. As a base is the Under Armour model  with the SmartWool playing the part of mid-layer  and a Basin and Range hardshell as the outer.
Ross Robinson utilizing a three layer system while skiing in the Sierras. As a base is the Under Armour model, with the SmartWool playing the part of mid-layer, and a Basin and Range hardshell as the outer.

Breathability


The excellent breathability of this product benefits from its tight fit, which stretches and spreads the fabric out over the upper body. In turn, this creates large spaces for moisture to escape through into the outside air. Moreover, any sweat that does condense on the inner layer is quickly wicked away by the internal checkerboard pattern. The Base 4.0 proved to be one of the most breathable products in this review, along with the tasc Base Layer and Lifa Stripe Crew.

This top is great for outdoor workouts and high intensity activities in cold weather  as it transmits any moisture produced very quickly to the external environment.
This top is great for outdoor workouts and high intensity activities in cold weather, as it transmits any moisture produced very quickly to the external environment.

Comfort and Fit


We found the Base 4.0 to be the least comfortable model amongst its other competitors in this review, but we'll start off with the positives. It doesn't itch whatsoever, and we didn't experience any chafing under the arms. And if you're into showing off your upper body, this product should be your top choice.

Now that we've covered the pros, on to the cons. This top is tight, and physically restricting. It didn't stop of from raising our arms, but it did push back against upward movement and almost snapped our arms back down into a relaxed position. Also due to the tight fit, whenever this shirt moved into a different position, it stayed there instead of falling back into place.

We were constantly readjusting the sleeves and waist of this base layer. We wished for longer sleeves in this model, as seen in the also form-fitting, but better performing, Arc'teryx Rho AR. As the thumb loops caused discomfort when utilizing them, we pretty much avoided them all together. Even the neck fit too tightly, uncomfortably and constantly reminding us that it was there and leading to some chafing in extended use.

The thumb loops on this model cause too much discomfort too be very useful  especially for extended periods.
The thumb loops on this model cause too much discomfort too be very useful, especially for extended periods.

Under Armour was one of the first companies to popularize the tight fitting base layers that have become ubiquitous amongst athletic apparel companies. This popularity is difficult to understand given how uncomfortable this top is to wear. Lastly, in terms of style, this top is best left under cover of other layers, unless there's someone you're trying to impress with your physique.

Drying Speed


Coming in 27% slower in our soaked to dry test than the fastest-drying top from Helly Hansen, this contender lands in the middle of the pack. Although our test provides a good starting ground for understanding a base layer's performance in this metric, it did have some limitations. We expect this model to dry even faster when worn than when suspended from a clothes hanger. As the tight-fitting fabric stretches over the torso, its surface area contact to the air will increase and speed up the drying process.

The waffled cells of these two products (Patagonia on the left  Under Armour on the right) helped increase their breathability and drying speed simultaneously.
The waffled cells of these two products (Patagonia on the left, Under Armour on the right) helped increase their breathability and drying speed simultaneously.

Durability


A close-up of some differences in seam construction. From left to right  the Capilene Midweight  Merino 250  Merino+ 160  Merino Midweight  and Base 4.0.
This Under Armour top feels strong, although fairly thin. We liked that the outside of the shirt was smooth and resistant to snagging, even on velcro. The seams appear to be quality, and we saw no signs of damage or wear after the three month testing period. The main potential problem we foresee is due to the tight fit that stretches the thin fabric across the torso, which is a constant stress on the seams holding the shirt together. Especially noticed under the arms, there are no gussets to reduce this stress. We found that the Mountain Hardwear Microchill 2.0 had the highest level of durability, scoring a 9 out of 10 in this metric (it's also the cheapest contender in the review).

Layering Ability


The close fit that is great for increasing breathability and showing off your muscles limits layering ability. While this can be worn quite effectively as a next-to-skin layer, it is uncomfortable when worn over anything else. For a more comfortable contender that offers a higher level of layering ability, the Smartwool Merino 250 takes the cake.

Layering up with the Base 4.0 from Under Armour. The mid-layer pictured here is the Patagonia R1 Hoody  which won the Top Pick in our review of fleece jackets.
Layering up with the Base 4.0 from Under Armour. The mid-layer pictured here is the Patagonia R1 Hoody, which won the Top Pick in our review of fleece jackets.

Best Applications


Through our experiences with this product, we think the Under Armour commercials portray the best uses of this product pretty accurately; the Base 4.0 is designed for high intensity, low duration athletic activities like football, soccer, or other organized sports in cold weather. It will feel pretty great underneath a jersey during an outdoor winter match or game. Its strengths in breathability and wicking overshadow its deficiencies in comfort and layering, and using it during periods of high intensity will counteract its lack of insulation.

Value


Costing $85, this base layer is the fifth-least expensive model in this review. However, it only offers a solid value if you intend using it within its limited applications, or to show off some juicy pecs and 'ceps. For $60, you can take home the Best Buy winner, The North Face Warm, which ranks better in our fleet.

The Under Armour top was a solid first layer for an afternoon on groomed trails.
The Under Armour top was a solid first layer for an afternoon on groomed trails.

Conclusion


The Under Armour Base 4.0 certainly impressed us with its excellent performance in breathability, making it a good option for cold weather workouts and team sports, as its marketing makes clear. We didn't find it to offer much utility in the backcountry, though, where recreation is frequently accompanied by intervals of high, low, and no activity. We weren't psyched to wear this top for extended amounts of time, either, due to its poor comfort and annoying fit. Overall, we much preferred the more versatile base layers found in this review.

Ross Robinson
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