I had a great question from SixTwoThree recently that was first in line to be answered. It's especially a great question now that the weather is getting nicer and those of us on the coast can take advantage of beach days... and beach runs :)
Q: As you know, I've been slowly recovering from knee surgery. My P.T. advised me to run on the beach, which I've been doing religiously. I know it's gentler on the joints, so it will prolong my triathlon career; however, I'm really curious how to gauge my slower times without biting the bullet and running on pavement. What do you think? Is there a rule of thumb to go by? [My pace] varies by how deep the sand is that day as much as how good I'm feeling in a
workout. Either way, these beach runs feel like brick workouts because my legs
feel so much heavier when running in the sand. I'd love your opinion. Especially when it comes to fitting in long runs. Should I just swap out times versus distance? -- SixTwoThree
A: First off, to anyone interesting in sand running, I would not recommend just going out and doing lots of miles on the sand if you have limited to no experience doing so. Sand running time & mileage needs to increase in baby steps because the instability of the surface can negative consequences. However, sand running can be great for building strength, focusing on proper technique and increasing cadence. Just proceed with caution.
Thus, it's best to use time as your gauge for run workouts, not distance, especially when first incorporating this. Reason being, it's almost guaranteed that most people will run slower on the sand than on asphalt or other surfaces, even if their miles are fewer. So your long run could be many minutes longer but you're still working just as hard if not harder.
The main reason you're slower: You're not getting as much push-off from the ground. It's pretty simple, really. Imagine running on a nice springy track vs. sand. You sink into the sand--the deeper & looser the sand, the more you sink--and thus you're having to work extra hard to propel yourself forward. So don't get down on yourself if your mile times are off!
There's not really a "rule of thumb" that I'm aware of in terms of time/speed transfer from sand running to runs on harder surfaces, but I can almost guarantee running on sand will make you faster when you run on asphalt (avoid concrete please!). It's a good idea to test this, especially with a race coming up (SixTwoThree is doing CA 70.3). Run on a harder surface and note the differences in time and feel. Plus, your half-Ironman will be on a combo of asphalt, concrete and sand, so you need to get some exposure to varying surfaces. (No surprises on race day!)
So, SixTwoThree, slower running is not a reason to get frustrated about your time, and your PT was wise to advise it given that you're well recovered. There are many benefits to running on the sand if you are careful... yes I'm taking it even further :)
1) By being forced to run slower in the sand you have more of an opportunity to concentrate on form and technique while still getting a killer cardio workout. By form and technique, I'm talking everything: your stride, cadence and how you strike; your core strength and stability; and your posture and how you "hold" your upper body. Think about leaning forward, really lifting those legs up and maintaining a good turnover.
2) It's great for building that aerobic engine even if you're overall miles of your sand runs are low. This is helpful post-injury*, early in the season or even if you're at a point in your season where you need to add in another run to the weekly routine--breaks up the monotony. It's great cause you don't have to do so much in the sand and you still get some big endurance benefits.
3) After some experience, eventually you can start incorporating a little speed work on the sand and go more anaerobic to help increase your VO2max and whatnot, but do so with extreme care. Do short drills and work your way up to longer efforts. It's best to do any speed work on hard-packed sand. Don't always expect your numbers to match up with your track sessions in terms of speed.
4) Sand runs are a strength training session in essence. The sand's surface is always different and morphing, so your foot lands at different angles and your legs/hips are adjusting to what's beneath, which is all great for building strength in the foot, ankle, leg and beyond. But that can also be dangerous: The unstable nature of sand can put extra stress on certain areas (i.e. Achilles), and it can even lead you into "tweaking" something like your ankle if you're not careful (another reason not to worry about running your fastest on the sand).
*Only do sand running post-injury if you've had full clearance from your doctor and team of people in charge of your rehab.
Bottom line of Sand Running:
-Yes, you're going to go slower in the sand. But that will likely transfer over to faster running on harder surfaces.
-You can anticipate being more sore and even more tense in certain muscles from sand runs. This might require more recovery time.
-Don't overdo it. As I say with barefoot running, do it in small doses as an "accessory" to your overall run training. There are enough risks associated that it can be problematic.
-If you have prior issues with running, injuries, etc, I'd highly recommend talking with an expert before incorporating any sand running.
-Shoes? Your call. Wearing an old pair of running shoes might be wise, not necessarily for the support, but to avoid the risk of stepping on something gnarly, like glass. It's annoying to get sand in your shoes, but it's better than having a rusty nail in your foot.
-Last thing, important: Make sure you run on a stretch of sand that's flat and not sloped/at an angle. If you run on a slope, that can really jack up your body.
-Enjoy the beauty that sand running offers!
Thanks for the question, SixTwoThree :)