Why Understanding Total Daily Energy Expend Expenditure Could Help You Nail Your Next Race

Dr. Jeffrey Sankoff is an emergency room physician, triathlete, coach, and host of the TriDoc podcast. He breaks down the latest in multisport science to help keep you educated, healthy, and fast!

Omloop Het Nieuwsblad has recently been ridden, Milan San Remo is only a couple of weeks away and soon after that the Oceanside 70.3 will inaugurate the North American 70.3 racing season. All of that can only mean that spring is very much in the air at long last! With all the excitement of the warming weather and the chance to finally get outdoors to train on a regular basis, we can begin to turn our thoughts to some of the big events on the calendar and for fans of cycling like me, that includes the grand tours; the Giro d’Italia, the Tour de France and the Vuelta a Espana. 

• These three-week events are the pinnacle of cycling and have long been viewed as the epitome of human endurance performance as well. One of the reasons for this relates to the total daily energy expenditure (TDEE) put out by the professional cyclists who participate.

While studies have shown that well trained triathletes participating in an Ironman event can expend around 7000-8300 kcal over 12 hours equivalent to around 8-9 times their basal metabolic rate (BMR) this rate is not sustainable over time.

• In fact, in studies of ultra-long-distance events, athletes TDEE decreases with time such that as the duration of the event increases the TDEE decreases to a more sustainable 3-4 times BMR.

However, previous studies of professional cyclists in the Tour de France showed that they were able to sustain similar rates of TDEE for the entire duration of the event. This puts professional cyclists’ metabolic loads on par with those of “migratory birds whose type of exercise is considered the most metabolically costly form of sustained activity of all animals”.

A recent paper in the Journal of Applied Physiology reported on a case study wherein researchers looked at a question that many of us age group athletes often wonder about;

Is it possible for a mere mortal to complete the Tour de France route in the same time frame and if so, what would it take?

The short answer: Age groupers can do amazing things, but professional cyclists are on a whole different level.

The long answer: For this study, the researchers were interested primarily in energy expenditure. Specifically, could a well-trained age group athlete increase their TDEE and maintain sufficient intake to ensure no significant loss of body mass over the 21 days of cycling.

This is important because if the TDEE were to outpace intake then the cyclist would be unable to maintain their ability to perform over the duration of the event. One of the remarkable facts about professional cyclists on the tour is that they can perform at a consistently high level on the last day just as they did on the first and one of the major reasons for this is that despite their enormous TDEE, pro cyclists maintain their body weights without any change for the entire duration of the event.

• Put another way, pro cyclists take in as much energy as they expend so as to maintain their muscle mass and their ability to perform.

Who was being compared

For this study, two anonymous cyclists were compared:

• A 27-year-old professional considered an ‘all-rounder’. His FTP was 375W (5.6 w/kg), VO2 max 80.5 ml/kg per min and he was 180 cm tall and weighed 67 kg (5’11”, 148 lb)

• A 58-year-old amateur. His FTP was 286W (3.0 W/kg), VO2 max 45.4 ml/kg per min and he was 191 cm tall and weighed 96 kg (6’3”, 211 lb)

What they did

The athletes had dramatically different training regimens going in to the 2023 Tour but while the professional had a much more rigorous schedule, the amateur was no slouch! The professional averaged 18-22h and 650km per week while the amateur put in 10-15h/week for a year and a half with 15-20h and 320km per week in the 4 months prior to the event.

Another big difference related to the conditions on the road during the Tour. The amateur rode all of the stages one week prior to the Tour as part of a 22 cyclist group participating in a charity event. Thus, he did not benefit from the closed roads nor the drafting dynamics that the professional had as part of the pro peloton.

How they did

Both cyclists completed the event (21 stages, 3405km with 51805m of elevation). It took the professional 87h while it took the amateur 191h (39.3km/h vs 18 km/h). Average power was 232W (3.45 W/kg) for the pro and 144W (1.50 W/kg) for the amateur. The training stress score (TSS) for the pro over the Tour was 4753 while for the amateur it was 6904 reflecting the importance of the duration of activity in the calculation of TSS.

• Interestingly, the TDEE was higher for the recreational cyclist than it was for the professional. Over the course of the 21 days, the professional cyclist maintained his body weight while the amateur lost 1.5 kg (3.3 lb).

What can we conclude from this?

There is hope for us mere mortals that with the proper training, any of us can complete a grueling event such as the Tour de France though I would not get too excited and take this to mean that any of us could compete in the Tour de France as those two things are very, very different!

• Still, the researchers were surprised to find that even with far less training, a well-trained age group cyclist was able to sustain such a dramatic TDEE for such a sustained period of time. This indicated that cycling is a means not only for age groupers to achieve very high metabolic expenditures but to even exceed those attained by professionals.

The limit of TDEE is likely based on how much can be taken in through the digestive tract. Previous research had suggested that alimentary intake was restricted to around 2.5 times BMR in humans but this is clearly not the case as evidenced by our professional cyclist whose TDEE was almost 4 times his BMR for 3 weeks and yet he did not lose any weight at all suggesting that his intake matched his energy expenditure perfectly. What the actual ceiling is remains to be determined.

• For now, suffice it to say that long distance and duration cycling events are very much within the grasp of any age groupers who are willing to put in the time and the effort to train up to the level needed for the event and take in the massive amount of calories needed to sustain the TDEE.

Train hard, train healthy.