Perhaps it comes with age, or inadequate sleeping pads, but in recent years I've often found myself shivering through the night during fall backpacking treks. But the arrival of a revolutionary pad from Therm-a-Rest carries the warm promise of making those nights distant memories.

Staying warm in the backcountry always is a concern, and to deal with it a few years back I added a 15-degree down sleeping bag to my closet. Sadly, it wasn't accomplishing the task. Whether my aging body simply had a lower thermostat onboard, or the sleeping bag was mislabeled, remains for debate.

When I heard Therm-a-Rest was coming out with a new pad -- the NeoAir XTherm -- one it promoted as a four-season pad, I was intrigued. I also was somewhat leery, as my current sleeping pad was a Therm-a-Rest Prolight, and it wasn't achieving the desired result. So leery was I, in fact, that I picked up a Big Agnes Insulated Air Core Pad during REI's Labor Day Sale.

With a backcountry trek in Yellowstone National Park's "Cascade Corner" on tap for earlier this month, a field test was quickly scheduled.

When I received a demo version of the XTherm, which goes on the market in January, I was both astounded and even more curious than I had been when reading about it. It was tiny, at least in terms of sleeping pads, about the size of a quart-sized Nalgene bottle when rolled tight, and incredibly light, at just 15 ounces (for the regular size, 20 inches by 72).

How could something so outwardly slight keep me warm when the temp fell below freezing? But that's exactly what it did as I settled down onto it in our camp below Albright Falls. So cozy was this pad, which provides 2.5 inches of cushion when fully inflated, that it almost felt as though I was sleeping on a heating blanket while ice droplets were forming on my tent's rainfly just inches away from my face.

But what was driving this warmth? The pad was not filled with either down or synthetic insulation that could keep the ground's cold from seeping into my bones.

Here's how the Therm-a-Rest folks explain how they achieved a 5.7 R-Value with the XTherm:

The patent-pending multiple-layer design of the NeoAir Reflective Barrier achieves warmth in extreme conditions with multiple layers that reflect heat back to the user’s body and reduce convective heat loss to the ground. The patent-pending Triangular Core Matrix design creates internal walls that trap warm air while providing a stable, comfortable sleeping platform. Advanced fabrics and a tapered design offer exceptional compressibility, compactness and light weight.

   One side of the XTherm is silver, the other grey, leading me to consider the possibility that the silver side was meant to reflect my body's heat. However, I later learned, the colors really are insignificant in that aspect. But the grey side is a higher-denier fabric (70 denier nylon with soft grip) that helps keep the pad in place on the floor of your tent -- no backsliding.

The top is a finer, 30 denier High Tenacity Nylon, which also helps keep your sleeping bag from scooting around while you doze.

Not entirely surprising, these pads are not exactly inexpensive. With sizes ranging from small (20 inches by 47 inches, 11 ounces) to large (25 inches by 77 inches, 22 ounces), the XTherm's MSRP ranges from $149.95 to $219.95. Included are a stuff sack and patch kit.

But if you sleep cold, as I do, shouldn't you treat yourself to the resulting warmth and the light weight for a great night's sleep in the backcountry?

Traveler footnote: For most users, those not heading into the highest elevations on Earth, the NeoAir Pump Sack that's built into the pad's stuff sack, is superfluous. It's designed to trap air in the sack, and as you roll up the sack the air is forced into the pad. If you've got lots of time and little breath to spare, this might be a good option. But if you're at lower elevations and can spare a dozen or so deep breaths, inflating the pad is much easier and quicker the old-fashioned way. And since there's no insulation inside, a little moisture from your breath won't do any harm.