We’re incredibly proud to share this work by Georgia Harris, exploring the management of tibial bone stress injuries. Drawing on her clinical experience and the latest evidence, Georgia provides practical advice for fellow physiotherapists to help guide assessment, rehabilitation and return to sport in this challenging area.
Returning to Running After Tibial Bone Stress Injury: What Physiotherapists Need to Know About Speed and Surface Selection Kelly Sheerin, Georgia Harris and Duncan Reid - AUT Sport Research Institute NZ (SPRINZ).
Tibial bone stress injuries remain one of the most challenging overuse injuries encountered by physiotherapists working with runners. While most clinicians have well-established frameworks for managing pain, restoring function and progressively reintroducing running, there remains considerable uncertainty regarding two practical questions frequently asked by patients: ‘How fast should I run?’ and ‘What surface should I run on?’
While existing clinical guidelines suggest that sport- specific terrain and speeds should guide preference during return to running, these are modelled off elite runners (1,2) . How these recommendations relate to non-elite runners and how they guide progressions through return to running still leaves a great deal of uncertainty for clinicians.
To address these questions, we conducted a review of literature that synthesised the evidence from 34 research studies examining how running speed and surface characteristics influence biomechanical variables associated with tibial loading during running.
Why speed and surface matter
Bone stress injuries develop when repetitive loading exceeds the bone’s capacity to remodel. During rehabilitation, the aim is to progressively restore loading while avoiding excessive stress that could delay healing or contribute to recurrence. Many rehabilitation protocols recommend gradual progression of running distance and volume before introducing faster running or more demanding terrain.
However, these recommendations have historically relied more on expert opinion than strong evidence. Likewise, advice regarding whether runners should begin on grass, treadmills, tracks or roads has often been inconsistent.
This review examined whether changes in running speed and surface characteristics influence biomechanical variables believed to reflect tibial loading, including peak tibial acceleration, vertical loading rates, impact forces and estimates of tibial stress.
Speed consistently increases tibial loading
Perhaps the clearest finding from the review was the consistent effect of running speed. Across the available literature, increasing running speed was associated with increasing magnitudes of several biomechanical variables linked with tibial loading. Faster running generally produced higher peak tibial acceleration (3, 4, 5) , greater ground reaction force loading rates (3,6) and increased estimates of tibial stress and tibial bending moments (7, 8, 9, 10, 11) .
Although individual studies used different protocols and outcome measures, the overall direction of evidence was remarkably consistent. Faster running appears to expose the tibia to greater mechanical loading than slower running. For physiotherapists, this supports the current clinical practice of delaying faster running until athletes have successfully tolerated the restoration of basic running volume. Early rehabilitation should prioritise pain-free, controlled running rather than pace or intensity.
Importantly, the review also highlighted that there is no evidence defining an optimal running speed during rehabilitation. While slower running generally reduces loading, the literature does not provide clear thresholds or progression rates that clinicians can confidently prescribe. Individual responses to loading remain highly variable, meaning symptom response and functional progression should continue to guide decision-making.
Surface selection is less straightforward
In contrast to the relatively consistent findings regarding speed, the evidence surrounding running surfaces was considerably more complex. Traditional rehabilitation advice has often promoted softer surfaces, based on the assumption that they reduce impact loading. Grass, trails and compliant surfaces have therefore commonly been recommended during early return to running. The current evidence challenges this assumption.
Across the studies, no single surface consistently demonstrated lower tibial loading than all others. Comparisons between treadmills, grass, concrete, asphalt, synthetic tracks, trails and artificial surfaces produced mixed findings, with many studies reporting minimal differences between surfaces (12) .
Perhaps most surprisingly, grass was not consistently associated with lower tibial loading. Several studies actually reported higher peak tibial acceleration on grass than on harder surfaces (13, 2, 14) . This reflects an important concept in running biomechanics. Runners naturally adapt their movement according to surface characteristics. On softer surfaces, individuals may increase leg stiffness or alter muscle activation patterns, potentially offsetting the expected reduction in external loading (15, 2, 16) . Consequently, softer does not necessarily mean less stressful for the tibia.
Gradient appears more important than surface characteristics
One of the strongest findings regarding terrain was related not to the surface itself but to running gradient or incline. Both uphill and downhill running altered biomechanical variables associated with tibial loading, although in different ways. Downhill running consistently increased impact-related variables, including peak tibial acceleration, vertical impact peaks and loading rates (18, 19, 20, 21) . These findings suggest that downhill running substantially increases the rapid loading experienced by the tibia. Steeper uphill running also increased estimated tibial stress and bending moments in modelling studies (7) , indicating that sustained climbing may also increase tibial loading through different mechanical pathways.
Taken together, these findings suggest that physiotherapists should initially avoid both significant inclines and declines during early return-to-running programmes. Flat, level running surfaces allow more consistent loading and reduce unnecessary biomechanical variability during the healing process.
Why treadmills may be useful early in rehabilitation
Although evidence comparing surfaces was somewhat inconsistent, treadmills emerged as a practical option during the early phases of rehabilitation. Several studies demonstrated lower tibial acceleration during treadmill running compared with some overground conditions (13, 14, 17) . Beyond the biomechanical findings, treadmills offer several practical advantages that are highly relevant in rehabilitation. Running speed can be precisely controlled, gradients can be eliminated, environmental variability can be reduced, and the load that runners are exposed to from session to session can be easily manipulated and carefully monitored.
The evidence therefore supports treadmill running as a sensible starting point when reintroducing running after tibial BSI, particularly during the early stages when controlling cumulative loading is a priority. However, treadmill running should not be a long-term strategy. As rehabilitation progresses, runners should gradually transition towards the surfaces they will ultimately encounter during training and competition.
Progress towards sport-specific surfaces
An important message from the review is that rehabilitation should ultimately reflect the athlete’s intended sporting environment.
A trail runner who only trains on treadmills during rehabilitation may experience substantially different loading patterns when returning to uneven trails. Similarly, a road runner who rehabilitates exclusively on grass may encounter insufficient biomechanical demands if they were to return abruptly to asphalt.
Rather than searching for one universally best surface, clinicians should view surface progression as a key load-management variable. Beginning with predictable, controlled conditions before gradually introducing sport-specific terrain appears to represent the most logical progression.
Clinical implications
Several practical recommendations emerge from the evidence that align well with contemporary load- management principles.
During the early return-to-running phase:
Prioritise gradual restoration of running volume before increasing speed.
Begin on flat, predictable surfaces where running conditions can be carefully controlled.
Avoid significant uphill and downhill gradients during initial progression.
Consider treadmill running as an effective early rehabilitation environment.
Gradually introduce the surfaces the runner will eventually encounter in training or competition.
Importantly, these recommendations should complement, not replace, the broader management of bone stress injuries. Successful rehabilitation still requires attention to factors such as training load, nutritional status, bone health, relative energy deficiency in sport, muscle strength and running technique.
Where evidence is still lacking
Although this review provides valuable clinical guidance, it also highlights significant gaps in the evidence. Most studies examined biomechanical variables in healthy runners rather than in individuals recovering from bone stress injuries. Furthermore, biomechanical measures such as peak tibial acceleration and force loading rates are surrogate markers of tibial loading rather than direct measures tibial bone stress or injury risk. Consequently, it remains uncertain exactly how changes in these biomechanical variables translate into recurrence of bone stress injury.
There is also little evidence describing the optimal progression of running speed throughout rehabilitation, the interaction between speed and surface, or whether different runner sub-populations require different rehabilitation strategies.
