You are not imagining it: Cycling indoors is harder than outside

Training is never meant to be easy, but for those who push themselves hard indoors and outside there is often a common observation: indoor training feels harder and invariably requires greater commitment and higher energy output. 

The question is: why? 

One of the main factors that contributes to higher perceived exertion indoor vs outdoor is heat. However, wind velocity, body position and attention also play a role in creating unique differences between indoor and outdoor exercise performance.

Firstly, though, let's look at the advantages of indoor training.

Why we train indoors

Most cyclists complete indoor and outdoor training sessions over the course of a season. The decision to train indoor vs outdoor may be dependent upon the weather or personal preference.

Related: The best indoor training apps

Even in the best conditions, indoor cycling does create a better environment for the most intense exertion without fear of losing focus on bike handling or your surroundings. Anyone who has tried to complete an FTP test outdoors will know how tricky it can be to find a stretch of road where you can truly empty the tank uninhibited by traffic, undulations and technical corners where the gas must come off.

Add to that the infinite variables surrounding outdoor training and sensors — power meters are affected by atmospheric pressure and temperature outdoors, which can reduce their fidelity. Indoors, the controllables are easily controlled. 

However, the fact that indoor training can feel so much harder is also a reflection of the fact that often the conditions are far from optimised.

So, let’s look at why indoor training is harder, and how we go about mitigating the effects.

Wind

A significant factor which makes indoor training more demanding is wind velocity. When training indoors, it is a good idea to install one or two fans that can replicate the constant circulation of air that’s occurring when you ride on the road. 

However, no matter how good your indoor training setup, artificial air circulation is ultimately inferior to the wind created by a moving bicycle and the prevailing meteorological conditions.

Read more: How do professional riders use Zwift in the off-season?

Natural air circulation envelopes the entire body and has been shown to lower skin temperature more effectively than similar conditions in a lab. It has been reported that male cyclists riding at 60% VO2max for 1hr in the wind (outside) had skin temperatures that were reduced by 0.68 degrees compared with indoor trials. 

Indoors, convective cooling is lower and may lead to an increased sweat rate which creates some dehydration and subsequent cardiac drift (a higher heart rate). All of which leads to feelings of higher exertion when riding indoors.

Body Position

One of the most overlooked factors in higher perceived exertion indoors is body position. 

When riding outside, a cyclist is constantly making micro adjustments to their position on the bike. Undulations in the route, short or long climbs followed by fast and sinuous descents require balance and a well developed sense of proprioception. 

Proprioception is knowing where your arms, legs and torso are in three-dimensional space. The world champions of proprioception are cats. In the unlikely event a cat falls from a fence or tree they will always land on their feet. For cyclists, proprioceptive skills are more rudimentary compared to cats, nonetheless we use our neural network in much the same way to maintain balance every second of an outdoor ride. However, indoors it is a different story. 

Here we are locked into a more narrow range of body positions. The options are to either ride on the hoods or down in the drops. This restricted range of motion leads to a more rapid onset of fatigue in prime mover and postural muscles because the same muscle fibers are being subjected to a constant load. Outdoor it is easier to spread this load across a wider muscle mass while side to side movements of the bike create leverage which can also assist in forward propulsion. 

Attention

Attention is also an important factor in the perception of difficulty within an indoor training session. 

The psychological awareness of physical exertion is commonly measured with the Borg RPE score. This is a scale from 6–20 that correlates well with physiological measures of heart rate, power output and blood lactate levels. 

The Tammen Attentional Focus Scale has also been used in research to examine the focus of cyclists during indoor and outdoor exercise. It is a 10-point scale ranging from 0 (complete dissociation) to 10 (complete association).

Dissociative thoughts are a disconnection with the task at hand and for cyclists include daydreaming, observing the surrounding environment or listening to music. Associative thoughts include paying close attention to breathing, pedaling technique or the power meter head unit. 

Research using the Tammen Attentional Focus Scale has found mixed results as to whether associative or dissociative thoughts are best for performance. However there does appear to be a higher tendency for associative thinking during indoor cycling. 

This increased awareness of either the surroundings or training session details can lead to higher feelings of perceived exertion (RPE) when riding indoors. It is also one of the reasons why online cycling platforms are so appealing, because they encourage dissociative thoughts which elicit lower feelings of effort.

The +/-20 watt rule

It is a well-known rule-of-thumb in coaching circles that for any indoor training session you should take +/-20watts off outdoor training targets. 

This number was not conjured by some mystic combined wisdom of the global coaching community. Instead, there is some very good research that indicates +/-20w as being a solid start point for establishing your indoor training zones. 

The golden thread that runs through this field of research is that most riders are able to produce more power outdoors than inside the laboratory with a minimum increase of 11% and some of the largest being 70%. In terms of power, reports have demonstrated that after a series of repeated 40km time trials competitive cyclists can produce 11w to 23w more when they train outside. 

Tips for making indoor cycling ‘feel’ easier:

So, if you find indoor cycling a little more challenging than riding on the road, you are not imagining it. Indoor cycling is harder. But if you follow these tips, you will be fully equipped to make your next indoor session more productive and a lot more enjoyable.

• Accept that indoor training is hot, but understand there are ways to help with training in the heat.
• Make sure you have good airflow within your training room.
• Pay close attention to your body position. Try moving around in the saddle after each set of intervals or alternate from the hoods to the drops every five minutes. Changes in cadence can also help redistribute the load over a greater range of muscle fibers. 
• Set up your training room for dissociative thinking. This can be achieved by watching a movie, a group ride on your favourite online training app or via music streaming. 
• The +/-20w rule: take 20 watts off your outdoor training zones. For some intense intervals you might need to subtract more than 20w.