Cycling vs. Running ‘which burns more fat?’ and ‘which is harder?’
-By: Tomas Swift-Metcalfe
Last modified: November 14, 2014
I’ve followed a thread on the Facebook and there some views aired on ‘which burns more fat’ and ‘which is harder’.
So which is it? Lets find out:
Running is a high impact active, it involves repeatedly striking the ground with impact force of roughly 2 -3 times body weight. That means that as a 70 kg human being, your leg muscles, bones and ligaments are subject ~210 N of force every single step of the way. Now cycling, on the other hand has negligible impact. The bike is supporting your body weight and eccentric forces acting on the musculature and bones are negligible. It’s worth noting this is true of road cycling, but not mountain biking.
Muscle contraction type also differs. In cycling muscle contractions are concentric, that is the muscle is lengthening. This is also the type of contraction that produces the least force. In running there’s the whole array of muscle contraction type: concentric (in propulsive phases) and eccentric on the breaking phases. The degree of muscle activation in the running movement actually occurs just before ground contact in running as the body ‘pre-empts’ the impact.
So which is harder on the muscles? Running by far. This is the reason we see bike races lasting weeks, while just one marathon takes weeks to recover from. You can do a massive amount of cycling before needing to stop.
Why is it ‘easier’ to run hard than cycle hard? In cycling the volume of muscle used by the activity and requesting oxygen from the respiratory system is less (60% versus 80% in running).
Ventilatory and cardiovascular stress (heart + lungs)
In both sports, trained athletes are able to attain ‘VO2max’ -that is maximal aerobic capacity, or the maximum amount of oxygen that your body can absorb. The body, like a combustion engine needs oxygen to produce energy: fuel + oxygen ≅ energy; heat + work. VO2max represents a ceiling of how much energy can be ‘burned’ aerobically. Where VO2max can’t be attained it’s unlikely that that exercise will be as effective at burning fat as these ‘big muscle group’ exercises. Other factors leading to performance in sport are efficiency and energy derived through other (anaerobic) mechanisms, also at which point one reaches Lactate threshold (LT), which varies from sport to sport and basically defines rates of sustainable exercise.
For sub-maximal exercise, a roughly linear relationship exists between heart rate and energy expenditure -regardless of exercise modality; the unit cost of oxygen per amount of energy remains very similar regardless of ‘metabolic substrate’ (that’s fuel; Carbs, Fat, Protein). So what we’re seeing is if you cycle at the same intensity you run, you’ll burn round about the same amount of energy!
Excess post-exercise oxygen consumption (EPOC) is also about the same when comparing cycling and running, so post exercise fat burning remains about the same for both.
So which is harder on ventilatory/cardiovascular system? They’re the same more or less, it depends how hard you exercise and not how you exercise.
So which burns more fat? We’re back to the question of exercise intensity, rather than modality…
N.b. one important aside: LT will likely come a different stages in the same person doing the two sports. Generally LT is higher while running than cycling, except trained cyclists: If you’re a runner, runner is ‘easier’. If you’re a cyclist, cycling is easier. If your neither, then running is easer. Non-cyclists find it hard to reach VO2max on a bicycle.
The much ignored nervous system: the one that actually gets you up, out and exercising is obviously also an important factor.
Both sports provoke a large amount of cognitive load to people new to them: There are literally billions of ‘factors’, degrees of freedom open that the mind has to deal with. Think about what’s going on: posture, muscle activation, sensory feedback from the body, sensory feedback from the environment, cognitive interference, spatial processing and navigation, etcetera… An awful lot more is happening that just sitting on the couch! This can cause an overload of the neural structures that have to process the information. Hence it is interpreted as ‘unpleasant’ by those unaccustomed to momentum sports. People beginning sport often make subconscious efforts to reduce cognitive load by exercising indoor, listening to music, exercising at a reduced intensity, picking exercise modalities which minimize the amount of, or disassociating themselves from the activity at hand by using distraction techniques, such as counting strides, singing, thinking about something else.
With practice a person develops automatic ‘coping mechanisms’ (schema) where things that would normally take up their attentional resources become automatic.
So which is ‘less stressful’ I am not aware of a comparison between exercise modality and rate of arousal (although it probably has been done), so have to go on common sense here. I would guess running causes a greater amount intrinsic stimuli while cycling causes a greater amount of stimuli from the environment. In colloquial: Running hurts more than biking, but the movement is slower, so you have less things like cars, obstacles, dogs and potholes to deal with, biking is more stressful due to environmental factors. Given rates of participation in sport I’d guess about the same as cycling and running have a very similar amount of participants.
Coming next we’ll get Ricardo to throw swimming into the equation.
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