Quick Answer
Grass running reduces joint impact by 9–16% compared to asphalt, develops stabiliser muscles that road running under-trains, and is the ideal surface for easy runs, recovery sessions, and base building. Use grass for 1–3 sessions per week. Keep tempo runs and intervals on road or track for race-specific conditioning.
The Science: How Grass Reduces Running Impact
When your foot strikes the ground, the energy of impact must go somewhere. On hard surfaces like concrete, the surface absorbs very little — approximately zero percent of the impact energy returns through the ground. Instead, nearly all the force is transmitted up through the foot, ankle, shin, knee, hip, and lower back. The body compensates by increasing muscular activity in the lower leg by approximately 15% compared to softer surfaces — a protective mechanism that becomes fatiguing at high mileage.
On grass, the surface itself deforms slightly under load, absorbing a meaningful proportion of impact energy before it reaches the body. A PMC study measuring sacral accelerations in runners across three surfaces (concrete, synthetic track, and grass) found the highest mean and peak impact accelerations on concrete — confirming that runners face measurably greater biomechanical loads on hard surfaces. Research specifically comparing grass and asphalt found that grass reduces foot-strike forces by 9–16% per contact — a statistically significant reduction that accumulates enormously over long-distance running.
The practical consequence is that the same aerobic training stimulus — the same pace, the same duration, the same heart rate — can be achieved on grass with substantially less load on passive structures (bones, tendons, ligaments). This is the core reason grass belongs in every runner’s rotation, particularly during high-mileage phases where cumulative impact load is the primary injury driver.
Benefit 1: Reduced Injury Risk From Impact
The majority of running injuries are overuse injuries — stress fractures, shin splints, IT band syndrome, patellar tendinopathy, plantar fasciitis — caused not by any single catastrophic event but by repetitive load accumulating faster than the body can adapt. The primary variable determining this load is training volume combined with surface hardness.
Grass directly addresses the surface component. A runner logging 60km per week on concrete exposes their bones and tendons to a substantially higher cumulative impact than the same runner covering the same distance on grass — even at identical paces and effort levels. For runners who are building mileage, managing a niggle, or returning from injury, shifting easy runs to grass is one of the fastest and cheapest ways to reduce injury risk without reducing training volume.
Shin splints and stress fractures — two of the most common impact-related injuries — respond particularly well to surface modification. The tibia absorbs impact forces directly on hard surfaces; on grass, those forces are distributed and attenuated by the surface itself before reaching the bone. For runners with a history of bone stress injuries, grass should be the default surface for any run that isn’t specifically race-preparation work. Our running injuries and pain resource library covers the full range of common running overuse injuries and evidence-based management approaches.
Benefit 2: Stabiliser Muscle Development
Road and track surfaces are uniform — every footstrike lands on a perfectly flat, predictable surface that requires minimal neuromuscular adjustment. Grass is never perfectly flat. Even well-maintained grass surfaces have subtle undulations, soft patches, and slight directional variations that require the body to make constant small balance corrections with every stride.
These corrections activate muscles that road running systematically under-trains: the intrinsic foot muscles (which control toe position and arch stability), the peroneals and tibialis posterior (lateral ankle stabilisers), the hip abductors (glute medius and minimus), and the deep core stabilisers. These are precisely the muscles associated with injury resilience in runners — weakness in the hip abductors, in particular, is consistently linked to IT band syndrome, runner’s knee, and iliotibial band pain.
Head coach at Team USA Minnesota, Dennis Barker, describes grass as outstanding for balance development because the uneven surface engages larger muscles in the feet, ankles, legs, and hips that don’t move as much on a flat, even surface. The same principle that makes grass beneficial for balance also means it requires more muscular effort for the same pace — which produces a strength stimulus that flat road running cannot replicate at equivalent effort levels. These stabiliser muscles are also specifically targeted by the exercises in our core exercises for runners guide and gym exercises for runners guide — grass running complements this strength work by training the same muscles in a dynamic, sport-specific context.
Benefit 3: Ideal Surface for Zone 2 and Recovery Runs
Zone 2 running — easy aerobic effort at 60–70% of maximum heart rate — is the foundation of endurance development. The purpose of these sessions is to build aerobic capacity, mitochondrial density, and fat oxidation efficiency without accumulating the fatigue that limits adaptation from harder sessions. To fulfil this purpose, Zone 2 runs must impose minimal physical stress beyond the cardiovascular stimulus.
Grass is the ideal surface for Zone 2 work precisely because it reduces impact load. A 60-minute Zone 2 run on grass delivers the full aerobic stimulus while significantly reducing the bone and tendon load compared to the same run on road. This means the recovery cost of the session is lower — leaving more physiological capacity for the quality sessions (tempo runs, intervals) that drive fitness gains.
Recovery runs — short, very easy sessions designed to promote blood flow and active recovery between hard efforts — benefit from the same logic. The softer surface reduces eccentric muscle loading and the micro-damage that accumulates with hard surface running, allowing genuine recovery rather than adding to the fatigue the session is supposed to clear. For a full guide on how to structure your easy running effort correctly, our Zone 2 running pace guide covers effort calibration, pacing, and how to tell when you’re running truly easy.
Benefit 4: Foot and Ankle Strength
The foot contains 26 bones, 33 joints, and over 100 muscles, tendons, and ligaments — a complex structure that modern running shoes and uniform road surfaces systematically under-challenge. When every footstrike lands on the same flat, hard surface in the same orientation, the intrinsic foot muscles perform minimal work. The shoe absorbs variation; the foot simply transmits force.
On grass, each footstrike is slightly different — the surface gives a little, tilts fractionally, or offers a subtly different texture. The foot’s intrinsic muscles actively respond to these variations, working to maintain position, stabilise the arch, and control push-off. Over time, this natural variation strengthens the small muscles that support the plantar fascia, control toe-off mechanics, and maintain arch integrity — reducing susceptibility to plantar fasciitis, Achilles tendinopathy, and metatarsal stress injuries.
Running barefoot on short, well-maintained grass takes this further. Brief barefoot grass sessions — 5–10 minutes at the end of a regular run — dramatically increase sensory input to the foot and activate intrinsic muscles that even minimalist shoes partially insulate. This is a technique used in elite distance running programmes worldwide, and one that carries minimal risk when introduced gradually on flat, well-maintained surfaces.
Benefit 5: Heat Reduction in Summer Training
Grass surfaces absorb significantly less solar radiation than concrete or asphalt — both of which retain heat and radiate it back toward the runner during warm-weather training. Running on dark asphalt in Australian summer conditions means running above a surface that may be 15–20°C hotter than the ambient air temperature, adding meaningful heat stress to an already hot training environment.
Parks, ovals, and grass reserves stay cooler because vegetation transpires water, and the surface itself has lower thermal mass. For Australian runners training through summer — particularly in Melbourne, Brisbane, and Sydney where summer training conditions are demanding — shifting easy runs to grass surfaces in parks provides genuine thermoregulatory benefit alongside the impact-reduction advantages.
Surface Comparison for Runners
| Surface | Impact load | Injury risk profile | Best used for | Key limitation |
|---|---|---|---|---|
| Grass | Low | Ankle sprains (uneven terrain) | Easy runs, recovery, base building | Slower pace; not race-specific |
| Asphalt/road | Moderate | Overuse injuries (shins, knees) | Tempo runs, race-specific training | High cumulative impact at volume |
| Concrete | High | Stress fractures, shin splints | Short distances only | Highest biomechanical load of any surface |
| Synthetic track | Low–moderate | Asymmetric loading (curves) | Intervals, speed sessions | Left-leg dominance; can't do long runs |
| Trail | Low–moderate | Acute ankle injuries (2.8× higher than road) | Strength, variety, mental refresh | Ankle sprain risk; technical demands |
| Treadmill | Low–moderate | Altered biomechanics vs outdoor | Bad weather; rehab; controlled pace | Assisted stride; less proprioception |
For a detailed comparison of grass versus concrete specifically — including when to prioritise each surface for different training goals — our running on grass vs concrete guide covers the full surface debate. For guidance on treadmill running as an alternative surface option, our treadmill vs outdoor running guide covers the biomechanical differences and when to use each.
When NOT to Use Grass
Tempo runs and threshold sessions. The energy absorption of grass makes it harder to maintain precise pacing — the same effort produces a slower speed than on road. Tempo runs are designed to train at a specific physiological intensity (lactate threshold), which is best calibrated on a firm, consistent surface. Running tempo efforts on grass will slow your pace without changing the training stimulus — potentially misleading your pacing calibration for road races.
Interval sessions. High-intensity intervals require precise pace control and a surface that gives accurate feedback on effort. Track or road is preferable. Grass intervals are possible, but pace data will be unreliable and the surface energy-absorption makes true maximal effort harder to sustain consistently.
Wet conditions on uneven ground. Wet grass is slippery, and wet grass on uneven terrain combines two ankle sprain risk factors simultaneously. After heavy rain, switch to road or treadmill for safety.
Road race preparation phases. In the final 3–4 weeks before a road race, the majority of running should be on road surfaces to condition the legs specifically for race-day demands. A runner who has done most of their training on grass will find early road race kilometres harder on the legs than necessary.
For hill running specifically — which is often most accessible on grassy terrain — our hill running guide covers how to use gradient effectively for strength and endurance development, and our running slope guide explains how incline changes the biomechanical demands of each stride.
How to Integrate Grass Running Into Your Training Week
| Session type | Recommended surface | Why |
|---|---|---|
| Long run | Mixed road/grass or grass | Reduce cumulative impact; preserve legs for the week |
| Easy/recovery run | Grass (preferred) | Maximum impact reduction; genuine recovery |
| Zone 2 base run | Grass or road | Grass reduces load without changing aerobic stimulus |
| Tempo/threshold run | Road or track | Accurate pacing; race-specific mechanics |
| Interval/speed session | Track or road | Precise effort feedback; maximal pace achievable |
| Hill session | Grass hills or road hills | Grass hills add stability challenge; road hills more race-specific |
| Returning from injury | Grass (start here) | Lowest impact reintroduction to running load |
Practical starting point: If you currently run all sessions on road, shift one easy run per week to grass for 4 weeks. Observe how your legs feel in the 24–48 hours after long runs and hard sessions. Most runners notice reduced leg fatigue and faster recovery when they introduce even one grass session per week.
For runners finding or accessing grass surfaces in Australia — athletics ovals, school grounds, parkrun courses, and golf course perimeters are all accessible grass options in most cities. Our guide to finding a running track covers how to locate athletics facilities near you, many of which have adjacent grass areas suitable for easy running.
Grass Running and Barefoot Strides
Well-maintained grass is the safest and most practical surface for barefoot running — specifically short strides at the end of a regular run. Barefoot strides on grass work as follows: after completing your main run, remove your shoes and socks and run 6–8 × 80–100 metre strides at approximately 5K effort on flat, closely-mown grass. Each stride takes 15–20 seconds. Total additional time: 5–10 minutes.
The benefits are specific and well-supported: increased proprioceptive input to the feet and ankles, activation of intrinsic foot muscles, natural promotion of midfoot or forefoot strike mechanics, and calf and Achilles loading that strengthens these structures progressively. Many elite distance running programmes include barefoot grass strides 1–2 times per week as a permanent feature of the training schedule.
The key precautions: inspect the surface before running (glass, debris, uneven ground), start with 2–3 strides and build to 6–8 over several weeks, and avoid if there is any current Achilles or plantar fascia pain. Calf soreness after the first session is normal and reduces with consistency.
Build Your Training Around Smart Surface Rotation
SportCoaching's running training plans are designed around the right sessions on the right surfaces — easy running on grass, quality work on road or track, and progressive load that keeps you healthy through an entire training block.
FAQ: Running on Grass
Is running on grass better for you?
For joint health and injury prevention, yes. Grass reduces foot-strike forces by 9–16% versus asphalt and engages stabiliser muscles that road running under-trains. For race-specific preparation, some road running remains important. The most effective approach is surface rotation — grass for easy and recovery runs, road or track for quality sessions.
Does running on grass build strength?
Yes — the slightly uneven surface activates foot, ankle, hip, and core stabiliser muscles that flat road surfaces don’t challenge. The same pace on grass requires more muscular effort than on road, producing a meaningful strength stimulus over time. Barefoot grass strides amplify this effect by removing shoe cushioning and forcing intrinsic foot muscle activation.
Is running on grass good for bad knees?
Yes — significantly more comfortable than concrete or asphalt. Grass absorbs 9–16% more impact per footstrike, reducing the load transmitted to the knee. Runners managing IT band syndrome, runner’s knee, or general knee discomfort frequently tolerate grass running when road running is painful. The main caveat: uneven grass increases ankle sprain risk, so be cautious on rough or wet ground.
How often should runners train on grass?
1–3 sessions per week is the most common recommendation. Easy runs, recovery runs, and Zone 2 base sessions are the best candidates. Tempo runs, intervals, and race-specific work are better on road or track. Runners managing overuse injuries can shift more sessions to grass without losing aerobic training quality.
What are the disadvantages of running on grass?
Increased ankle sprain risk on uneven terrain; slower pace for the same effort; difficulty maintaining precise pacing; wet grass is slippery; not always accessible in urban areas. For road race preparation, too much exclusive grass training means under-preparing the legs for road mechanics. Surface rotation solves all of these issues.
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