![\"\"](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/11\/CORE2_2_Web.jpg\")
The Core 2 heat sensor is used by much of the pro peloton. <\/p>\nSweat drips from every pore and my sorry excuse of a fan isn\u2019t cutting the mustard. <\/p>\n
I\u2019m 40 minutes into the first zone-two endurance workout of a new training plan and a combination of a few months off the bike and without turbo training in the early days of summer means my complexion isn\u2019t the only thing in the red. And things are about to get much harder.<\/p>\n
\u201cPause the workout and add your clothing layer\u2026 If you\u2019re using fans, turn them off,\u201d instructs my screen.<\/p>\n
I do as I\u2019m told, donning a decorator\u2019s boiler suit and woolly hat before remounting. What was a trickle turns into a torrent and I\u2019m soon completely drenched as my body attempts in vain to cool itself down. <\/p>\n
As the workout\u2019s intensity rises, so does my heart rate, and I\u2019m forced to delve deep into my mental reserves not to throw in the (increasingly sodden) towel. <\/p>\n
The Core 2 heat sensor is used by much of the pro peloton. <\/p>\n
After 15 minutes that feel like hours, I\u2019m done and peel off my extra layers for my cool down. \u2018Easiest\u2019 session of the training block complete, things are only going to get harder from here.<\/p>\n
I\u2019m layering up on the turbo trainer to put the Core 2 thermal sensor through its paces.<\/p>\n
Used by the majority of WorldTour and Women\u2019s WorldTour teams \u2013\u00a0both officially via partnerships and, in the case of Tadej Pogacar, paid for out of his team\u2019s pockets \u2013\u00a0the device\u2019s updated iteration is claimed to \u2018transform human performance\u2019 via the training protocol of heat adaptation. <\/p>\n
What is heat training?<\/p>\n
When it comes to heat training, the adage \u2018no pain, no gain\u2019 certainly rings true. <\/p>\n
First touted as a training technique back in the 1970s and 80s, the current vogue for adding temperature into the equation began in 2010 when a study that was published in the Journal of Applied Physiology showed<\/a> that heat acclimation improved VO2 Max<\/a>, time-trial performance and lactate threshold in both cool and hot environments, and had comparable benefits to altitude training.<\/p>\n Since then, more research<\/a> has shown an intensive five-week block can increase haemoglobin mass \u2013\u00a0the protein in red blood cells responsible for carrying oxygen to muscles \u2013 with greater volumes equaling a better aerobic capacity.<\/p>\n But why does it have this effect?<\/p>\n \u201cOur body always tries to keep homeostasis \u2013 a constant core body temperature \u2013 but when you’re generating forward movement or power, meaning muscle activation, you’re producing heat,\u201d explains Core product manager Tobias Schmid. <\/p>\n \u201cOur body is highly inefficient, and only around 20% of the calories we turn into energy are used for forward movement or power production on the bike. <\/p>\n “The other 80% is excessive heat, which is first stored in your body. We need to get rid of it and that’s where the core temperature increases, and your thermoregulatory system starts to get rid of this heat via different mechanisms, such as sweating.<\/p>\n \u201cThe cool thing about our bodies is that we can train that system \u2013 same as we can train our muscles, our lungs and hearts \u2013 and that can lead to quite interesting performance improvements.\u201d<\/p>\n Schmid explains that consistent heat training generally has two outcomes \u2013\u00a0short-term heat adaptation that can help improve performance in hot conditions and long-term haematological changes.<\/p>\n The former can \u201cdiminish the performance loss in the heat by around 26%\u201d by training your thermoregulatory system to become more efficient at cooling your core temperature \u2013 meaning you start sweating more quickly \u2013\u00a0which, in turn, enables you to maintain a higher power output in hot conditions or give you more of a buffer in cooler climates. <\/p>\n The latter, meanwhile, means your body can transport oxygen more efficiently to your muscles thanks to a greater haematological mass.<\/p>\n \u201cFor thermoregulation, a lot of your blood is diverged through the skin to get rid of the heat, and there is less blood available for the muscles,\u201d says Schmid. <\/p>\n \u201cBut over the long-term, your body adapts and makes more blood available for the muscle contraction.\u201d<\/p>\n Achieving these adaptations requires you to regularly elevate your core temperature to 38.5-39\u00b0C, along with an elevated skin temperature for sustained periods of between 45 and 80 minutes.<\/p>\n This can be done actively (warm-weather training, or overdressing while riding on the turbo trainer) or passively, such as sitting in a sauna post-exercise.<\/p>\n So, how long would you have to do this for?<\/p>\n \u201cIf you want to push it, you can get fully heat adapted in two weeks \u2013 it would be five to six sessions a week,\u201d says Schmid, before adding a noticeable increase in VO2 max would require three to five sessions a week for four to six weeks.<\/p>\n Putting your body under thermal strain is a delicate balancing act, though \u2013\u00a0as anyone who has suffered from overheating or sunstroke will know.<\/p>\n Historically, hitting the adaptation sweetspot and attaining an accurate reading of your core temperature safely has required ingestible temperature sensors, or more invasive techniques (rectal thermometer, anyone?). <\/p>\n The wearable Core sensor is aimed at overcoming these issues and making heat training more accessible in the process.<\/p>\n How does the Core sensor work?<\/p>\n \u201cCore temperature or heat strain is now measurable with Core,\u201d says Schmid. \u201cIt’s a new training tool, like a power meter for your thermal power.\u201d<\/p>\n The new iteration \u2013\u00a0the Core 2 \u2013\u00a0is 48% smaller and 30% lighter than its predecessor, has a modular design that makes it easier to mount to a heart-rate strap<\/a>, and now features a low-battery indicator, but its internal technology hasn\u2019t changed and functions in the same way as the first version.<\/p>\n The stamp-sized device slots onto a heart-rate monitor strap and sits directly on the skin. It has one sensor that measures skin temperature, while another is used to calculate your core temperature via thermal power.<\/p>\n \u201cThe heat flux sensor measures the thermal transfer through the sensor \u2013 from the skin to your environment \u2013\u00a0and that’s thermal power; if you’re working harder, your thermal power is higher. <\/p>\n “We have built a model that uses those signals to calculate your core body temperature.\u201d<\/p>\n While Core doesn\u2019t claim its accuracy is medical-grade, it\u2019s adoption, and use by the world\u2019s best athletes and coaches is an indication that the data it produces is of value.<\/p>\n How does its application work in the real world? On its accompanying app, it displays both skin and core temperature while the device is worn, but without a background in sports science, this raw data is like being given a power-meter reading with no context.<\/p>\n This is why Core has also introduced a heat strain index (ranked from 1-10) and heat zones (ranked from 1-4), which can both be displayed on a head unit or smartwatch<\/a>.<\/p>\n \u201cThe heat strain index says how hard your body is working to keep cool, or how high your heat strain is on the body using a combination of the core and skin temperature,\u201d says Schmid. <\/p>\n \u201cIt’s not a linear formula though because the heat strain on the body isn\u2019t linear depending on skin and core temperature. <\/p>\n “At the moment, it’s universal \u2013\u00a0for some, a three feels like five or six for others \u2013 but we\u2019re looking into individualisation.<\/p>\n \u201cWe\u2019ve also developed heat training zones, which are similar to power or heart rate zones,\u201d he adds.<\/p>\n Made up of four zones, they can be used to guide training and racing. <\/p>\n \u201cOn race day, for optimal performance, you want to stay in heat zone one or two. Heat zone three is where, according to the literature, the adaptations in the body happen. The fourth is a danger zone, so you shouldn’t spend a lot of time there.\u201d<\/p>\n After a session, your ride data contributes to your overall heat training load and heat adaptation score. <\/p>\n The former shows how much that day\u2019s training contributed to your heat adaptation, with it highlighting if you\u2019re at risk of overdoing it \u2013\u00a0\u201dprolonging recovery and draining you\u201d \u2013\u00a0while the heat adaptation score tracks your progress from thermal rookie (0-24% adapted) to heat accustomed (25-49%) through to heat adapted (50-89%) and eventually heat champion (90-100%).<\/p>\n Why are they used by pro teams? While this data is a useful addition to the training toolbox for amateurs looking to add a completely new strain on their body and therefore unlock potentially untapped performance gains, how does the Core benefit professional cyclists, who often live and train at altitude and therefore could have reached their haemoglobin mass ceiling?<\/p>\n \u201cMany cycling teams do heat training at sea-level for the heat [preparation] and to keep those altitude gains, but also to prepare for altitude camps they’re then doing,\u201d says Schmid. \u201cSo they’re cycling between heat, altitude, heat, altitude.\u201d<\/p>\n The data from the Core therefore enables them to prepare for extreme conditions such as those experienced at the Tour Down Under and La Vuelta and retain haemoglobin mass when at sea-level with regular maintenance sessions.<\/p>\n Is the Core sensor worth it?<\/p>\n After eventually cooling down, I check the Core app to find my first training session has only made a small dent in my thermal journey.<\/p>\n While the potential performance benefits are clear, and it\u2019s a more accessible, convenient, and at \u00a3264.95, affordable route to these gains than altitude training or sleeping in an altitude tent, the mental load required to get to the end of one session is comparable to an FTP test<\/a>.<\/p>\n And given the number and frequency of the workouts required, you\u2019d probably need to be a competitive age-group athlete (or masochist) for the Core sensor to truly \u2018transform\u2019 your performance.<\/p>\n","protected":false},"excerpt":{"rendered":"Sweat drips from every pore and my sorry excuse of a fan isn\u2019t cutting the mustard. I\u2019m 40…\n","protected":false},"author":2,"featured_media":258477,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[37],"tags":[4985,101,56,54,55],"class_list":{"0":"post-258476","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-cycling","8":"tag-cycling","9":"tag-sports","10":"tag-uk","11":"tag-united-kingdom","12":"tag-unitedkingdom"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/258476","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=258476"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/258476\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/258477"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=258476"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=258476"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=258476"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/11\/CORE_Lifestyle6.jpg\")
Acclimatising to riding in the heat has short- and long-term benefits. <\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/11\/GettyImages_2161884571-scaled.jpg\")
Saunas and hot baths after a workout are passive ways to boost heat adaptation. Getty Images<\/p>\n
\n![\"\"](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/11\/CORE2_App-1.jpg\")
Core’s app goes deep on data, while the sensor can also sync to your bike computer. <\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/11\/GettyImages-1157528522.jpg\")
The Core sensor can help you stay in your optimal heat zones on the hottest days. Getty Images<\/p>\n
\n![\"\"](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/11\/CORE_Lifestyle14.jpg\")
Athletes at the top of endurance sport have found marginal gains in the Core sensor. <\/p>\n