How track bends change the demands on each leg
Track season is here, and for many runners that means more laps, faster sessions and a return to spikes. It also means spending more time running around bends.
Your left and right legs do slightly different jobs on the bend. That can show up in how you move, the forces you produce and even your strength testing. The useful question is whether those differences matter for your symptoms or performance.
What changes on the bend
When running anticlockwise around a track, your left leg is on the inside of the bend and your right leg is on the outside.
To keep turning, you need to produce force towards the centre of the curve. At the same speed, a tighter bend requires more inward force. Increasing speed also increases that requirement. This is why lane choice and running speed are worth considering when looking at a track session. [1]
The two legs help meet that demand in different ways: in a study of six sprinters, the inside leg spent longer on the ground and showed greater ankle eversion, hip adduction and hip external rotation. In plain language, the ankle rolled inwards, the thigh moved further towards the midline, and the hip rotated further outwards. [2]
Another study of nine competitive sprinters found higher average vertical and ground reaction forces through the outside leg at both curve radii tested. Resultant force means the combined force across directions. These were averages over ground contact, rather than a statement about every peak force or every tissue. [1]
Most of this mechanics research involves small groups of sprinters. It helps explain what happens at speed, but we should be careful applying the same findings to an easy run around the local oval.
Does bend running make one leg stronger
It may contribute to some differences, although the answer depends on which muscles and which test you are looking at.
Giakoumis and colleagues tested eccentric hamstring strength in 44 elite track and field athletes. The 400 m athletes had greater right-sided hamstring strength. The researchers suggested that bend running could help explain this, but the study measured athletes at one point in time, so it could not establish the cause. [3]
An older study followed 25 sprinters and middle-distance runners through an indoor season. The left ankle invertors gained more strength than the right invertors, while the right evertors gained more than the left evertors. These are the muscle groups that turn the foot inwards and outwards. [4]
So there is no simple rule that the right leg will be stronger at everything. When looking at strength results, I’d want to know whether the difference is consistent with previous testing, whether it has changed, and whether it comes with pain or reduced performance. A percentage difference on its own gives me very little to work with.
What the injury findings actually tell us
A study of 201 elite track and field athletes recorded 85 calf muscle injuries over eight seasons. Of those injuries, 58% affected the right leg and 42% the left. That describes which side was injured in that group. It does not show that bend running caused the injuries, or that the right calf was weaker. [5]
The indoor-track study also found no significant difference in ankle strength changes between injured and uninjured runners. With only 25 participants, that does not rule out a relationship, but it certainly does not establish that the strength differences caused injury. [4]
I’d use the bend mechanics to help decide what to assess, while keeping the runner’s symptoms and history central to the assessment.
What I would check in the clinic
The first step is to get specific about the complaint. Where does it hurt? At what speed? Does it happen on the bend, the straight, or both? Has the runner recently returned to the track or changed their sessions?
Medial ankle pain on bends
If pain around the inside of the ankle is aggravated by bend running, I’d consider tibialis posterior strength, calf strength and endurance, and the response to relevant loading tests. Greater ankle eversion in a sprint study does not diagnose a tibialis posterior problem or tell us which runner will develop one.
Hip or groin pain on bends
Depending on the symptoms, I’d assess the hip abductors and adductors, the muscles around the outside and inside of the hip. I’d then look at tolerance of tasks that reproduce the running demands, and whether pain changes with speed or lane choice. A difference in hip position between legs may be part of negotiating the bend. Finding it does not automatically give us something to correct.
Compare the running itself
Where appropriate for the injury, comparing bends and straights at a similar speed can help identify what aggravates symptoms. If the bend is always run faster, it becomes difficult to separate the effect of speed from the effect of turning.
Building back into track sessions
A useful starting point is to look at how much bend running the athlete has actually done recently. Weekly kilometres can stay much the same while the amount of fast running on bends changes considerably.
For example, replacing a road session with track repetitions may also introduce faster running, spikes and more repeated bend exposure. I’d account for all of those changes when planning the session.
For a runner returning to track training, I’d consider:
Recent exposure to faster bend running.
The speed, number of repetitions and tightness of the bends.
How the session fits with the rest of the training week.
Symptoms during the session and how the runner responds afterwards.
Progression should match what the athlete can currently tolerate and what their event will eventually require. Strength work can address relevant deficits, while running provides the opportunity to build tolerance of the actual task.
For me, the aim is to build enough capacity in both legs for the athlete’s event.
If you need help with pain when running or returning to track sessions, book a running assessment at Health & High Performance in Mont Albert North.
References
Diaz GB, Alcantara RS, Grabowski AM (2024). Maximum velocity and leg-specific ground reaction force production change with radius during flat curve sprinting. Journal of Experimental Biology, 227, jeb246649. https://doi.org/10.1242/jeb.246649
Alt T, Heinrich K, Funken J, Potthast W (2015). Lower extremity kinematics of athletics curve sprinting. Journal of Sports Sciences, 33(6), 552–560. https://doi.org/10.1080/02640414.2014.960881
Giakoumis M et al. (2020). Eccentric hamstring strength in elite track and field athletes on the British Athletics world class performance program. Physical Therapy in Sport, 43, 217–223. https://doi.org/10.1016/j.ptsp.2020.03.008
Beukeboom C, Birmingham TB, Forwell L, Ohrling D (2000). Asymmetrical strength changes and injuries in athletes training on a small radius curve indoor track. Clinical Journal of Sport Medicine, 10(4), 245–250. https://doi.org/10.1097/00042752-200010000-00004
Kelly S, Polglass G, Giakoumis M, Pollock N, Shaw JW (2026). Calf muscle injury in elite athletics: an 8-season prospective cohort study. Journal of Science and Medicine in Sport, 29(3), 231–237. https://doi.org/10.1016/j.jsams.2025.08.019
