This guide covers how to add running alongside your FLEX programming without losing the strength and conditioning work the program is built on.
FLEX already has everything you need to plug running in. You just need to understand one rule and figure out which tier you fall into.
The One Rule: Running Replaces Conditioning Work. Performance Work Stays.
Your squats, deadlifts, presses, rows, all of it stays exactly as programmed. The conditioning piece is where running slots in. You swap the tool, not the work.
How to match it: open the app, look at what that day’s conditioning is asking for, and match the intent. Aggressive pacing? Run short and hard (think interval work). Forever pace? Run long and easy (long run). Moderate? Run moderate (tempo, threshold work).
Tier 1: “I Just Like Running”
No race. No goal. You just enjoy it.
Swap 1-2 conditioning sessions for running. Pick the longer, easier conditioning days. Optional easy jog on a rest day. Everything else stays.
Tier 2: “I Have a Race Coming Up”
5K, 10K, fun run, casual Hyrox.
Swap 3 conditioning sessions. For overall running development your runs should typically include:
- One fast speed session (replace a short/explosive day): 200-400m repeats, hard effort, full rest
- One moderate run (threshold or tempo session, replace a medium duration conditioning day 12-15 minutes)
- One long easy run (replace the longest conditioning day): 25-40 min, conversational pace
Time domains and distances are generalized. A long run for one person is 20 minutes, for another 2 hours.
Tier 3+: Half Marathon, Full, or Ultra
Or competitive Hyrox, but more on that in the Training for Hyrox with FLEX guide.
Tiers 1 and 2 work inside FLEX because the running demands are moderate. Serious running goals change the math. Your long runs need 60-90+ minutes. Speed work produces better results on fresh legs, not after squatting progressions.
At this level, you need a program where strength days and running days are separated so each session has one focus. FLEX gives you an extremely strong fitness foundation, but a serious running goal requires a program built for it. The FLEX isn’t going anywhere, it will still be here for you to pick up where you left off when you’re ready.
New to Running?
Start at Tier 1 regardless of your goal. 4-6 weeks minimum.
Running loads your joints and connective tissue differently than anything else in the program. Your cardio adapts in weeks. Your tendons and bones take months. That gap is where injuries happen. All runs easy. Walk breaks are smart. Once you can do 20-25 min continuously without joint pain, move up.
No wrong tier. Just the one that matches what you want right now.
