Take a quick look around the pro peloton and you’ll notice that not every rider has the exact same spinal posture on the bike. Examine the images below and you’ll notice how similar the spinal posture is of the number 1 and 2 riders in this years’ Tour de France, Jonas Vingegaard and Tadej Pogacar. Their spinal position on the bike, even under fatigue and maximal effort when racing, is about as perfect as it gets: a gentle curve from the pelvis to the base of the neck. Contrast this with the green jersey winner, Wout Van Aert, who has a more rounded spinal posture, yet it is clearly a very effective spinal posture for him.
As you can see there’s not a single spinal position that “must be followed” in order to succeed; however there are parameters or a range into which spinal position must fall if the rider is to be efficient enough to achieve an optimal performance.
To illustrate this further, a closer scrutiny of professional riders reveals that there are simply no riders with a completely straight / flat back (they all have a gentle or moderate curve). Similarly there are no riders with a very rounded back (what I like to call the “Sydney Harbour Bridge back”). There are some good reasons for this which I’ll elaborate on shortly; however I would like to note that these extreme postures do exist in the world of amateur cycling and are a common reason why cyclists develop back pain and seek a bike fit or clinical care. There is also a misconception that a straight spine, sometimes called a “neutral spinal posture", is essential in sport… Whilst this is true for a weight lifter or even for a sedentary activity like sitting at your desk, it is not true for cycling.
Why would your spinal posture actually matter on the bike?
As is usually the case, the answer is more complex than you might think and involves the inseparable factors of performance enhancement and injury prevention. Here is a brief summary of why you should consider your spinal posture on the bike:
Excessive spinal flexion (a “rounded back” posture) is linked to low back pain when cycling (Van Hoof et al 2012). We are talking about something more rounded than Van Aert’s posture here, a real “Sydney Harbour Bridge” spine. This alone is a good reason to consider your posture on your bike, since any pain will not only potentially force you to stop riding but will also result in reduced power output.
Excessive spinal flexion postures result in the low back extensor and abdominal (“core”) muscles switching off, a phenomenon known as “spinal muscle relaxation”. Over time if you continue to train in the rounded back position it causes atrophy and weakness in the torso muscles (Streisfeld et al 2016) which are risk factors for back pain and will certainly not assist in your performance.
The “switching off” of your back and abdominal muscles typically occurs at much lower levels of spinal flexion when sitting compared to when standing (Shinkle-Ivy et al 2014). Getting the spinal position right is thus crucial for cyclists whose entire sport is performed sitting.
When you are fatigued, such as towards the end of a race or long ride, it takes a lesser flexion angle to cause relaxation of the muscles (Descarreux et al 2008). This means that pushing the limits of your spine in your bike fit when pedalling gently probably won’t end well in racing – a mistake made with incredible frequency in time triallists looking for every minor improvement they can get to go faster… Some improvements aren’t an improvement at all, which they discover the hard way.
A reasonable question to ask would be “does an ideal spinal posture result in more power output?” Again the answer is a little on the complex side, since a stable posture and upper limb / torso position is required for the legs to generate power but the upper body itself adds very little power to the pedal stroke (in the order of 2-3%). The real reason the posture assists power output is best considered if we take the postural stability away - failure to have a stable upper body / torso / pelvis results in very significant power loss of around 10-20% (Turpin & Watier 2020).
So how do you develop an excellent spinal posture for riding? There are many factors that influence your spinal posture and stability on the bike so the answer really depends on identifying what is preventing your cycling posture from being appropriate and addressing the unique combination of factors relevant to you.
From a bike fitting perspective there is plenty of science and practical experience here at Cycle Physio which has shown the following things (at a minimum) to affect your cycling posture and stability:
Saddle shape and design
Saddle tilt
Saddle height
Saddle setback
Crank length
Foot length
Stack height
Reach to handelbars: also influenced by frame size
Drop to handelbars
Angle of brake hoods
From a musculoskeletal perspective, developing a good cycling posture will for many require some work on the part of the cyclist, addressing factors such as flexibility and strength deficits. “Develop” is the right word here – these changes take time and a considered approach as the type of muscle contraction and duration when cycling is rather different to that during a sit up or a plank exercise. This is especially true for junior cyclists and also for the more sedentary adult who takes up cycling later in life. A sports Physiotherapist like David Wadsworth is ideally placed to analyse and address and of the musculoskeletal short comings that might be impairing a good spinal position on the bike.
References:
Descarreaux M et al (2008): Changes in the flexion relaxation response induced by lumbar muscle fatigue. BMC Musculoskeletal Disorders 9:10.
Schinkel-Ivy A et al (2014): Quantification of the lumbar flexion-relaxation phenomenon: comparing outcomes of lumbar erector spinae and superficial lumbar multifidus in standing full trunk flexion and slumped sitting postures. J Manip Physiol Ther 37:494.
Streisfeld GM et al (2016): Relationship Between Body Positioning, Muscle Activity, and Spinal Kinematics in Cyclists With and Without Low Back Pain: A Systematic Review. Sport Health 9:75.
Turpin NA & Watier B (2020): Cycling Biomechanics and Its Relationship to Performance. J Appl Sci 10.
Van Hoof W (2012): Comparing lower lumbar kinematics in cyclists with low back pain (flexion pattern) versus symptomatic controls - field study using a wireless posture monitoring system. Man Ther 17:312.