Hot Spinning Back in the News

By Jennifer Sage On August 18, 2012 Under Contraindications, Medical, studio management

This article from the online fitness journal Greatist asks the question Are Hot Workouts Safe? I covered this topic back in January 2012 in this post. But this topic will keep resurfacing as more and more studios adopt gimmicks that they think will set them apart and increase their popularity. Many employ these gimmicks without doing their research, and in doing so, put their students and members at risk.

This article correctly challenges the belief that excessive sweating “clears away toxins” and that heating up a room, even “only” to 82 degrees, is inconsequential. They give some suggestions on how to tolerate the heat by staying hydrated and to slow the pace if it becomes unbearable. But I believe they left out a few major points about the dangers and misinformation of working out in an artificially heated environment. I left some suggestions in the comments section on the article, adding a few points that the author missed. Below is an edited version of what I posted on the web article. (Note: I am elaborating a bit more here since I didn’t want to leave TOO long of a comment on the article.)


You left out a couple of important factors in training at higher temperatures. For a given effort, heart rate increases but does not translate to a greater calorie burn (contrary to what some people might think). This means that when the temperature is higher than usual, one must train at a lower intensity to avoid overheating. While doing this, heart rate will still remain high. This increase in heart rate is incorrectly interpreted as meaning more work is being accomplished, and that in the process, more calories are being consumed. But this is incorrect. In the heat, power output will necessarily drop, and as a result, training stimulus and caloric burn is reduced. Ignore what your HR monitor says about your calories burnedcalories burned—it doesn’t know the difference and will give faulty “calories burned” totals in elevated temperatures. (Actually, the stated calories burned on HR monitors or cardio machines is almost always faulty, but that’s another topic…)

Elite athletes understand that they can’t train as intensely as they might need to when temperatures exceed a certain level. When training in hotter environments, they will avoid the higher temps at all costs; they train before sunrise, or they will train indoors, or if they must run/ride/train outdoors in the heat, they will move their training schedule around to avoid the higher intensity workout, and that particular workout becomes more of an endurance or recovery effort in lower training zone (as measured by power output or pace).

Do endurance athletes have to acclimate to the heat? Absolutely, and this means that over time they will perform better in the heat. But there is still an upper limit, and they still have to deal with reduced effort when it gets too hot. And more importantly, you never know the acclimation level or fitness level of every student in class.

What does this mean for the casual exerciser going to a heated indoor cycling class “on purpose”? It means that you are doing yourself a disservice. Your power output will be necessarily decreased, despite what your monitor tells you about your HR. As a result, over time, you will have much lower gains in overall fitness than you would have had you trained in less hot environments. Why do this to yourself on purpose? Stay cool as much as possible and you will give your body a much greater chance to improve strength, aerobic endurance, muscular endurance, lactate threshold, anaerobic endurance, aerobic capacity, anaerobic capacity, and power. This will result in much greater fitness gains and a greater number of calories burned.

Excessive sweating was disproven years ago to not equate to increased fitness or effort, or to lasting weight loss. Anyone who claims it does has not learned their exercise physiology.

For the studios that say their cycling rooms “never rise above 82 degrees,” (in this article Mimi Benz of The Sweat Shoppe makes this claim) that is doubtful. That is the STARTING ambient temp of the room. Put a bunch of hot sweaty bodies working hard and the temp will surely rise to potentially dangerous levels, especially if there is higher humidity. The studio where I teach starts at 68–70 degrees, which is the ACSM recommended temp for cardiovascular fitness studios, and it easily rises to the low 80s when the room is full—even with fans.

Personally, I’m surprised that students don’t rebel, especially in light of the fights that have been known to occur in some cycling rooms over the fans. I have some students who are so intolerant to heat, one of them brings her own fan.

But in this day and age, people are so gullible that they will believe anything, even to the point of hurting themselves.

Indoor cycling—or any cardiovascular exercise—in artificially heated rooms is dangerous and irresponsible. I’m shocked that facilities aren’t leery of the liability they are creating. Even the race director of the Boston Marathon issued a warning that it would be “dangerously hot” at 84 degrees (that’s 84 degrees outside where there is wind to aid in sweat evaporation). There are hundreds, even thousands of studies that have proven the dangers of training in the heat. The family of the first person that dies from heat-related problems in an overly heated cycling studio will very easily win a wrongful death suit, because a good lawyer will have access to a plethora of studies that clearly spell out the danger, and to expert witnesses that specialize in heat-related illnesses.

As leaders in the fitness industry (studio and club owners, coaches, instructors, etc.) we have a responsibility to our clients/students to do what’s right. Increasing the heat in the cardio or cycling room* does not benefit them, and it puts them at risk. It is not the right thing to do.

(*Please note that this discussion is about cardiovascular exercise, which raises internal body temperature. I’m not speaking about yoga or static weight training in the heat.)


3 Comments Add yours

  1. pascal hannecart
    August 19, 2012
    12:38 am #comment-1

    This ‘mode’ of working out in heated environment came from Hot Yoga, as for a lot of thing in the fitness world it is total missunderstanding of the original purpose … and as people nowadays have less and less commun sence they would trust any crazyness.
    As you explain in an heated environment the intensity HAVE to be adapted !!! Adaptation to heat is something really difficult, I am living in a crazy heat and humid area since 5 years, I am struggling training outdoor half of the years ? And I am sure I have less power than when I was living in a normal area.

    I know you ask not to mention it but I will puit just a remarq; one of the thing they say with Hot Yoga is that it help to eliminate toxin … I am not thinking the same, there are some studies and scientist that think the same: excess sweat is not really eliminate toxin and event it put a LOT more stress and toxin on liver and kidney !!! So this can be the opposite excess sweat produce more toxins !!!

  2. Jennifer Sage
    August 19, 2012
    3:11 am #comment-2

    Yes Pascal, there are “studies” that “prove” both sides. Both have a point. I’ve read what some scientists say that the additional sweating and stress from the heat actually produces more toxins. More studies are definitely needed.

    And BTW, I don’t care if you mention it! 😉 Posting this means I welcome discussion.

  3. Jennifer Sage
    August 19, 2012
    9:59 pm #comment-3

    Here is a study entitled The Cardiovascular Challenge of Exercising in the Heat, http://www.ncbi.nlm.nih.gov/pubmed/17855754
    Study was done at the Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex, UK, and was published in the Journal of Physiology in 2008.

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