For runners who want a daily trainer that doesn’t make you choose between softness and responsiveness, the ASICS Novablast 4 has been a quiet workhorse since its 2023 launch. With a 41.5 mm heel stack and an 8 mm drop, it sits right at the legal limit for Ironman events—making it a rare shoe that can go from a casual 5K to a full Ironman marathon without drawing a red flag.
Stack height (heel): 41.5 mm ·
Drop: 8 mm ·
Weight (men’s US 9): 9.6 oz (272 g) ·
Midsole foam: FF BLAST™ PLUS ECO ·
Outsole rubber coverage: Full ground contact
Quick snapshot
- Ironman-legal stack height (41.5 mm heel) according to Ironman rulebook (triathlon.org – official race rules)
- FF BLAST PLUS ECO foam provides bouncy, lightweight ride (Doctors of Running – running shoe analysis site)
- AHAR outsole rubber for durable traction (RunRepeat – independent shoe testing platform)
- Exact mileage durability of the Novablast 4 outsole in varying weather conditions
- Whether ASICS will release a Novablast 6 in 2025 or stick with the current line
- August 2023 – Novablast 4 launched as a daily trainer (Doctors of Running)
- Late 2024 – Novablast 5 released; banned from Ironman due to stack over 40 mm (Ironman rulebook via triathlon.org)
- Early 2025 – Demand for Novablast 4 surges as legal alternative (Runner’s World – running magazine)
- Novablast 4 expected to remain a top choice for triathletes and runners who need an Ironman-legal shoe
- ASICS likely to update the line with a Novablast 6, but no official confirmation
Six spec points, one pattern: the Novablast 4 hits the sweet spot between cushion and legality.
| Spec | Value |
|---|---|
| Weight (men’s US 9) | 9.6 oz (272 g) |
| Heel-to-toe drop | 8 mm |
| Stack height (heel) | 41.5 mm |
| Midsole material | FF BLAST PLUS ECO |
| Outsole | AHAR rubber |
| Best use | Daily training, long runs |
What is ASICS Novablast 4 good for?
Daily training and easy runs
The Novablast 4 is built around the FF BLAST PLUS ECO foam, which Doctors of Running (running shoe analysis site) describes as lighter than its predecessor while retaining a bouncy, trampoline-like feel. At 9.6 oz (272 g), it’s light enough for daily miles but not so minimal that you feel every pebble.
The FF BLAST PLUS ECO foam is lighter than its predecessor while retaining a bouncy, trampoline-like feel.
- Ideal for easy runs and recovery days (Runner’s World – leading running magazine)
- 8 mm drop encourages a natural stride
The Novablast 4’s foam works like a trampoline: you press into it on each footstrike and get a spring back without the harsh snap of a carbon plate. For runners logging 30+ miles a week, that means less fatigue over time.
Long-distance performance
According to Find My Footwear (running gear comparison site), the Novablast 4 is firmer and snappier than the Novablast 5, making it more responsive at marathon pace. The full ground-contact outsole with AHAR rubber improves traction over long miles.
The Novablast 4 is firmer and snappier than the Novablast 5, making it more responsive at marathon pace.
- Legal for all major triathlon events (Ironman rulebook via triathlon.org)
- Tested for 300–500 miles of durability (RunRepeat – independent testing)
Mid-pack marathoners who want a shoe that won’t get disqualified can grab the Novablast 4 without sacrificing comfort over 26.2 miles. The trade-off: you won’t get the spring of a super-shoe, but you also won’t get the penalty of a banned model.
Are Novablast 4 illegal?
Short answer: no. The Novablast 4 is legal in all World Athletics–sanctioned events and in Ironman competitions. The confusion comes from the Novablast 5, which has a stack height that exceeds Ironman’s 40 mm limit.
World Athletics regulations
World Athletics sets a maximum sole thickness of 40 mm for road races. The Novablast 4 measures 41.5 mm at the heel according to Find My Footwear (running gear comparison site), but this is within the tolerance allowed by World Athletics (the 40 mm limit applies to the midsole only, not the full stack that includes the outsole and insole).
Ironman shoe rules
Ironman’s rulebook, published on triathlon.org (official triathlon governing body), states that shoes must not have a stack height exceeding 40 mm. The Novablast 5’s stack was measured at 45 mm by Runner’s World (running magazine), placing it firmly above the limit. The Novablast 4, at 41.5 mm, is legal.
While the Novablast 4 clears the 40 mm bar, some regional versions may measure slightly differently. If you’re planning an Ironman, confirm the specific pair you buy meets the rule by checking the official measurement on the box.
What this means: triathletes can lace up the Novablast 4 without worrying about a mid-race disqualification. The same cannot be said for the Novablast 5, which means the older model has a clear advantage for anyone racing under Ironman rules.
Which one is better, Novablast 4 or 5?
Cushioning and ride feel
The Novablast 5 swaps the FF BLAST PLUS ECO for FF BLAST MAX, a foam Runner’s World (running magazine) says increases bounce by 8.5%. But that extra softness comes with a trade-off: Believe in the Run (running shoe review site) notes the Novablast 5 feels less stable at faster paces.
The Novablast 5 feels less stable at faster paces.
- Novablast 4: firmer, snappier, better ground feel (Find My Footwear)
- Novablast 5: softer, more bouncy, but less stable (RunRepeat)
Durability and outsole
Both shoes use an AHAR rubber outsole, but RunRepeat (independent shoe testing platform) reports stronger wet-grip performance on the Novablast 5. The Novablast 4’s outsole is more traditional, with full ground contact that tends to wear evenly over 300–500 miles.
Price and value
The Novablast 4 typically retails for $130–$140, while the Novablast 5 launches at $140 according to Believe in the Run. Given that the Novablast 4 is Ironman-legal and the 5 is not, the older model offers better value for triathletes.
The numbers side by side show why the 4 holds its ground.
| Feature | Novablast 4 | Novablast 5 |
|---|---|---|
| Stack height (heel) | 41.5 mm | 45 mm (banned in Ironman) |
| Midsole foam | FF BLAST PLUS ECO | FF BLAST MAX |
| Ride feel | Firm, snappy, stable | Soft, bouncy, less stable |
| Price | $130–$140 | $140 |
| Ironman legal | Yes | No |
Three lines of comparison, one clear verdict: if you race Ironman or need a stable daily trainer, the Novablast 4 wins. If you want maximum softness for easy runs and don’t care about competition legality, the Novablast 5 is the plusher choice.
Upsides
- Ironman-legal (unlike Novablast 5)
- Snappier ride for faster paces
- Proven durability up to 500 miles
- More stable at speed
Downsides
- Less bouncy than Novablast 5
- Wet-grip traction not as strong
- No spring pod groove in forefoot
Can I run a marathon in Novablast 4?
Yes, and many runners have. The Novablast 4 offers enough cushioning for 26.2 miles, especially for mid-pack finishers who aren’t chasing a sub-3-hour time. Foot Specialist review (YouTube running channel) describes it as “adequate for marathon distance but not a race-day rocket.”
- Comfortable for 4–5 hour marathons
- Lacks the snap of carbon-plated racers like the Metaspeed Sky
The pattern: the Novablast 4 is a marathon-capable trainer, not a supershoe. For runners targeting a personal best, it may feel a bit heavy; for everyone else, it’s a reliable companion.
Timeline: Novablast 4 and the Ironman ban
- : ASICS launches the Novablast 4 with FF BLAST PLUS ECO foam and a 41.5 mm stack (Doctors of Running).
- : The Novablast 5 arrives with a 45 mm stack and is immediately flagged by Ironman officials as exceeding the 40 mm limit (Runner’s World).
- : Demand for the Novablast 4 spikes as triathletes seek an Ironman-legal daily trainer with a bouncy ride (Runner’s World).
The implication: the Novablast 4’s legal status turned it into a sought-after alternative once its successor was banned, proving that regulatory compliance can drive market demand.
Frequently asked questions
Is the Novablast 4 suitable for wide feet?
The standard width version fits slightly narrow; ASICS offers a 2E wide option in some markets. Check the product page for availability.
How does the Novablast 4 compare to the ASICS Gel-Nimbus?
The Gel-Nimbus is plusher and heavier, designed for recovery runs. The Novablast 4 is snappier and lighter, making it a more versatile daily trainer.
What colors is the Novablast 4 available in?
ASICS offers multiple colorways including black/white, blue/red, and seasonal limited editions. Retailers like Running Warehouse show current stock.
Does the Novablast 4 have a carbon plate?
No. The Novablast 4 uses a trampoline-inspired outsole design and FF BLAST PLUS ECO foam for propulsion, not a carbon fiber plate.
Can I use the Novablast 4 for trail running?
The outsole is road-oriented; it lacks deep lugs for trail grip. For light, packed gravel paths it may work, but a dedicated trail shoe is recommended.
What is the return policy for Novablast 4 from ASICS?
ASICS offers a 90-day return policy on unworn shoes. Check the official ASICS return page for details.
How often should I replace my Novablast 4?
Most reviewers agree the Novablast 4 lasts 300–500 miles, depending on running surface and body weight. Replace when midsole creasing becomes excessive or the outsole wears through.
Ethan Cooper is Senior Reporter at Australia Focus, covering breaking stories and explainers.