WFR #7: Ground Contact Time (Float) | Wed 14th Jan, 7:30pm | Prospect Park Weekly Form Run

[sof...@gmail.com]

When: Every Wednesday at 7:30 p.m. (run leaves at 7:37 abouts).

Where: Find The Big Red Pointer(TM) (center of the map, click here).

Distance: A single figure 8 lap of Prospect Park, ~4.6139 miles.

Optional Distance Sub-group: 3 miles or less if that's helpful (please let Run Leaders know).

Today's Direction: Right as you face the park at startup.

Pace: Welcome to all. Fun.

AQI: We're monitoring Air Quality Index here and have been asked to not run if the local index exceeds 125.

New Stuff:

I dragged this week's bubble ("Ground Contact Time") to the top of the topics hierarchy and gave it a good shake. The result was this diagram. "Ground Contact Time" is supported by "Head Bob", "Short Strides", "Quiet Feet". "Forward Tilt", and "Passive Stride Recovery".

Just in case you'd like to explore, here's a pretty QR Code for Week #19:

Towards the end of Week #19 Notes (below "The Mantra"TM) there are links to all the WFR weekly topics.

This week's focus: Ground Contact Time (injury prevention, economy/efficiency, performance, speed)

TL;DR: More forward push per ground contact time = less ground contact time per distance run.

Ground Contact Time can be a confusing metric. It represents how long your foot will remain in contact with the ground, for a given distance run. For a given distance run, the smaller this number is, the faster that distance will be run. If you have a relatively fixed stride length (i.e. leg length, landing spot under or behind your knee, given amount of leg stretch behind you before "Passive Stride Recovery" takes over), minimizing Ground Contact Time per mile involves a faster leg movement and essentially, a higher Cadence or Stride Turnover Rate.

Ground Contact Time is often measured per stride but consider that if that were all that was important, jumping up and down could minimize your Ground Contact Time but not contribute to your forward speed!

One of the most interesting biomechanical characteristics related to running is that the longer your foot spends in front of your center of gravity, the more your landed foot contributes to slowing you down (braking force) - increasing your resultant Ground Contact Time. Reducing that braking force (and reducing your Ground Contact Time), requires your landing foot to be closer to, or behind, your center of gravity, which pitches you forward. To stop you falling flat on your face you have to increase your center of gravity's momentum (i.e. your forward speed).

That's why we're looking at this backwards. If our Ground Contact Time was not decreased when we ran faster (while practicing our other techniques), we'd use a lot more (misplaced) energy just to prevent us falling flat on our faces. Who knew! As a further aside - when you're not listening to music, you can actually hear that misplaced energy on foot strike.

If a bunch of the other WFR hints are properly practiced (Stride Length, Foot Landing Position and Placement, Quiet Feet, Stride Turnover Rate, Passive Stride Recovery, Head Bob Control, Ankle Angle), then Ground Contact Time becomes essentially an emergent measurement rather than a technique driver.

Ground Contact Time Per Stride is measured by Apple Watch as ms per stride. Stride Rate (cadence) is also given. Arguably more useful than "You Fell On Your Face", which we already have on Apple Watch. (ps I personally *really* like Apple Watch - esp. for running (and falling) metrics).

Floating people! We're working on floating. So I know a lot of you aren't going to want to hear this, but efficient runners keep almost all of their weight on the forefoot throughout the weight-bearing phase of each stride cycle. This provides both shock absorption and energy return for propulsion for the next stride. This really sucks because I just can't quit heel contact, especially when I'm tired! (See... when I get tired I use more misplaced energy to prevent "Face Planting" which will probably be WFR #20 one day).

Something to think about!

OB Biomechanics links for further reading:

https://www.scienceofrunning.com/2011/02/180-isnt-magic-number-stride-rate-and.html?v=7516fd43adaa

https://runblogger.com/2011/09/running-speed-human-variability-and.html

https://www.trainingpeaks.com/blog/ground-contact-time-and-running-performance/

Related WFR Topics
"Head Bob" #1 (bubbles), "Short Strides" #3 (bubbles), "Quiet Feet" #6 (bubbles), "Forward Tilt" #8 (bubbles), "Passive Stride Recovery" #12 (bubbles).

Reading Bubble Diagrams:

Bubbles in the pictures are individually linked to the most recent notes. They are now no longer pictures (hooray), they're scalable vector displays.

Topics are related to each other. Some more or less directly than others. Bubble Diagrams (e.g. this week's topic bubble diagram) illustrate how they are related. Bubbles nearest the top are more directly related to this week's topic. The path to the top illustrates a chain of related topics. Topic bubbles are expanded once in their highest position (most closely related to this week's topic) and are colored blue (or colored black if this is a topic's only appearance). Duplicated bubbles are colored green, which is no less important than a blue colored bubble at the same vertical distance from the root.

Lines that join topic bubbles have been colored. Blue connecting lines illustrate a child topic (lower) supported by its parent topic (upper... think waterfall). Purple connecting lines illustrate the child topic supporting its parent topic. Black connecting lines indicate bi-directional (mutual) topic support. Lightly colored connecting lines indicate topics that are pulled out of the way, as the level they occupy is too crowded. One day 3D (AV) will allow us to walk through bubble diagrams (like tinkling mobiles hanging from your ceilings) and currently lightly-connected bubbles will just be viewable at a different angle (by spinning the view) and not colored differently. One Day... ahhh... One Day.

📢 ANNOUNCEMENTS 📢

📱Join Heylo before Feb 1 ✅

NBR is moving to a new communication platform that’s purpose-built for running clubs.

Heylo makes it easy to find weekly runs, see upcoming races and events, stay on top of club announcements and socials, and chat with your teammates—all in one place.The transition will be completed by February 1, 2026 so please be sure to sign up before then using this link.

📢 Weekly Daddy Joke 📢

Q: Why can't dinosaurs have a better Ground Contact Time than me?

A: Because they're extinct!