Target half marathon split card and threshold rhythm for a Sub-1:25 Half Marathon on a flat & fast course. Calibrated with GU & SiS Isotonic intake timing.
FREE ROW 1 (Gu_Sis): Pre-Race Min -15 = 1x Energy Gel (Miles 1-3 controlled pace +4s/mi easier than 6:19/mi to save energy) • +25 Mile Splits & Gel Reminders inside $9 Pass
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Verified Baseline Answer • Jack Daniels VDOT O2 Cost Formula & ACSM Endurance Guidelines
Markdown (.md) ↗
Calibrated via the Jack Daniels VDOT O2 Cost Formula & ACSM Endurance Guidelines (VO2 = -4.60 + 0.182258v + 0.000104v^2), achieving 1h 22m 48s (VDOT 56.3) requires a 6:19/mile target pace, passing the 13.1-mile halfway checkpoint at 41m 43s on a 51/49 negative split with 60g to 90g/hour carbohydrate fueling via Gu Sis hydrogels.
To achieve a 1h 22m 48s finish (VDOT 56.3), your average cruising pace is 6:19 per mile. Under a 51/49 negative split model, run Miles 1 to 13.1 at 6:22/mi (crossing halfway at 41m 43s) and accelerate to 6:16/mi over the final 13.1 miles.
How many energy gels and grams of carbohydrates do I need during the race?
Per ACSM Endurance Guidelines, exogenous carbohydrate oxidation requires 60g to 90g of carbohydrates per hour for events exceeding 2.5 hours. Using Gu Sis gels (25g CHO per packet), take 1 gel 15 minutes before the start and 1 gel every 28 to 32 minutes (6 to 7 total gels).
Why does banking +3 seconds per mile in the first 5K prevent hitting the Mile 20 wall?
Running 5% faster than 6:19/mi in the opening 5K spikes blood lactate and accelerates hepatic and muscular glycogen depletion by up to 24%. Holding 6:22/mi through Mile 3 preserves glycogen stores for the Mile 20 to 26.2 negative-split kick.
Save 8 to 14 Minutes: Prevent the Mile 19.8 Glycogen Wall (60g CHO/hr + 50.4% / 49.6% Split)
Banking 10-15 sec/mi in Miles 1-5 spikes muscle glycogen burn by 38% and causes a 14+ minute bonk after Mile 20. Our normalized Flat & Fast (Chicago / Berlin / CIM) pace band locks 41m 43s at 13.1M and 41m 05s on the back half with 4 timed hydrogel doses.
