Are Thermals Good for Trekking? Pros, Cons, and Better Alternatives
If you’re heading off on a trek at high altitude or a cold-weather excursion, thermals may seem like the ideal solution for staying cozy and warm during chilly mountain weather. But experienced trekkers as well as outdoor experts advise against wearing thermals when trekking; though great as an evening base layer, they could cause harm when used during treks. Thermals are an integral component of high-altitude trekking attire, but many trekkers think thermals should be worn throughout a trek despite being designed as post-trek wear. There are several reasons for this practice; to understand them better it helps to understand how thermals function: thermals act as base layers in cold conditions that directly contact skin to retain body heat while preventing heat loss; polyester can often be blended with materials like Lycra or wool for added comfort and flexibility; ultimately these layers come under two categories known as Dynamic and Static layers which our Trek Leader, Nitin Rana describes as Dynamic and Static thermal layers respectively.
Thermal Trap Body Heat
Thermal clothing is designed to trap body heat, which is useful when not moving much, such as when sleeping in a tent. But during physical activities like trekking, your body generates both heat and sweat that the thermals capture too quickly, leading to too much perspiration buildup within them and leaving you feeling uncomfortable and sticky over time.
Wet Thermal Creates Risk.
Thermals that become saturated with moisture due to sweat or unexpected precipitation may take an inordinately long time to dry, especially in mountain environments with low temperatures and damp air. Clinging closely against your skin, wet thermals may quickly drain your body heat while heightening hypothermia risk during periods of inactivity or as night falls when temperatures fall dramatically.
Ventilation Problem
Thermals’ tight design and use of materials designed to trap warmth can limit airflow significantly, which may be beneficial when not physically active; however, when engaged in physical activity, it can cause your body temperature to quickly rise, leading to feelings of discomfort, heat stress, or even dehydration.
Lack Flexibility
Restrictive Thermal Layers Certain thermal layers lack flexibility and may restrict mobility when traversing steep inclines and declines. A garment designed with moisture-wicking capabilities, such as a dry-fit top or lightweight fleece, may offer greater manoeuvrability while maintaining comfort.
- Dynamic thermals are lightweight and comfortable breathable thermals designed for outdoor activities like trekking. Their stretchy synthetic fabric provides flexibility and ease of movement, offering warmth while quickly drying off with moisture-wicking properties. Static thermals may cause discomfort as they’re usually made of thicker wool fabrics compared to dynamic ones.
- Thermals may not be ideal trekking gear: when layering up for an outing, make sure the layer closest to your skin is breathable and moisture wicking; this allows full range of motion. Thermals do not make an ideal option in these instances.
- Trekking requires physical exertion that causes sweating even at cold altitudes, which in turn leaves your thermals damp with sweat as their materials, such as merino wool, cotton or synthetic blends that don’t dry quickly, may make this hard. Therefore, wearing damp thermals during the day could leave them wet when night falls; damp thermals actually makes you colder instead of providing warmth.
- Thermal clothing during a trek may lead to increased sweating compared to regular clothing, potentially leading to dehydration at higher elevations where Acute Mountain Sickness (AMS) presents a serious threat. This increases sweat production, which in turn may increase dehydration risk significantly.
- When sweat accumulates on thermal clothing during a trek and remains in contact with your skin for too long, it can lead to skin irritation and increase the chances of developing rashes.
- Thermals serve as an insulating layer intended to snugly encase your body for warmth retention, but this may impede your ability to move freely while trekking and lead to discomfort during trekking expeditions.
- For treks in warmer conditions, long-sleeved t-shirts may provide an effective alternative to thermals. When venturing out into colder climates, layering up with fleece or a down jacket is ideal. If you find that dynamic thermals provide more flexibility while drying more quickly.
- Thermals can be especially helpful in mountainous regions where temperatures can quickly decline in the evening or at night, where daytime temperatures range between 10-15 degrees Celsius and temperatures drop significantly during the nighttime hours, even as low as zero! When this happens, thermals provide invaluable warmth – just put them on once the sun has set at your campsite – the key being wearing them while your body still retains warmth – they act as heat insulators by blocking cold from entering, keeping you cozy until it is time for bed.
Conclusion
Thermals can be an integral component of winter-weather clothing, but should only be worn post-trek. Their purpose is to trap heat within and help keep you warm; however, under physical exertion, they could increase sweat accumulation, restrict airflow, and make you uncomfortable–possibly even cold when wet! Wearing them while trekking could result in extreme sweating, skin irritation, and dehydration, as well as an increased risk for hypothermia in case temperatures suddenly decrease. Choose flexible, breathable, and moisture-wicking layers in the morning that allow flexibility and airflow, and save thermals for nightfall when drying off and relaxing at the campsite. They’ll keep you snugly warm through winter nights in the mountains. Be smart when trekking: layer strategically and allow your gear to move with you instead of against you.
About Author
Anoop Rawat (Admin TrekUp India)
Anoop has worked for 5 years as a Trek Leader with TrekUpIndia, leading numerous treks across the diverse and challenging terrains of Uttarakhand and Himachal Pradesh. He holds a degree in Geology with a specialization in Geographic Information Systems (GIS) from UPES Dehradun. During his academic years, he actively applied his classroom knowledge in the field—most notably by contributing to a glacier research project on the Jundar Glacier in the Har Ki Dun Valley, Uttarakhand. Write Anoop at anoop@trekupindia.com
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