Hi all,

I am likely to be doing a lot of my training on grass tracks/fields for the forseeable future (for various injuries including injury prevention and lack of access to tracks) and am looking to find a general conversion factor for pace differences between the track/road and grass.

The best I could find from google was Alberto Salazar's quote: “Running on grass is 10 seconds slower per mile than running on the track,� Salazar said as he put down the last cone. “It’s great for building strength, but it’s not easy, especially if you run on your toes. Galen hates it.� (http://www.nytimes.com/2007/10/28/sport ... yt&scp=269)

Which is around 2.5sec/lap or 400m, 6.25sec/km for the metric minded.

I'm not sure of the basis for Salazar's conversion, and would be interested to know the outcome of any formal studies or experiences people have had.

Also I'd be very interested to know if this speed decrease is a lot different depending on footwear i.e spikes vs flats vs normal runners as I would think using spikes has a strong effect on a grassy surface but do not intend to do all my workouts in them.

Thanks in advance.

I used to train on grass every sessions because thats all i had access to living in a country area...but we always trained on goal pace (this is for 800m) so if my goal was to run 1:52 on track i would train my sessions based on that pace...it didnt matter wether i was on grass or not.

all of my 400 TT on grass were pretty much 2 sec slower then what i was running on track at the time as well.

i don't think is any one magic rule for training times on grass, it would all depend on how hard the ground is and the amount of grass there is.

it's also going to depend on how you run, like it says in that article it's harder for people that run on their toes, because the energy returns are not the same as say an athletics track. if you went and dropped a tennis ball on grass it would hardly bounce at all, if you drop one on a track it will bounce a lot. just keep that in mind

having gone up to stawell on the weekend i saw some very good runners that absolutely struggled runnin on the grass.

the only way to figure it out is trial and error.