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January 1, 1970 Β· 0 views
GU Energy Gel vs Clif Shot Bloks: Gels vs Chews for Long Runs
GU Energy Gel and Clif Shot Bloks are two of the most widely recognisable names in endurance sport nutrition. Both have been around for decades, both are available at aid stations in Australian running events, and both maintain loyal followings across the spectrum from first-time half marathoners to seasoned ultra runners. But they're fundamentally different products in format, consumption experie
GU Energy Gel and Clif Shot Bloks are two of the most widely recognisable names in endurance sport nutrition. Both have been around for decades, both are available at aid stations in Australian running events, and both maintain loyal followings across the spectrum from first-time half marathoners to seasoned ultra runners. But they're fundamentally different products in format, consumption experience, and practical application.
This comparison goes beyond simple preference and examines the evidence: which format actually delivers carbohydrates more effectively during running, which is better tolerated by GI-sensitive athletes, and which suits which specific race and training scenarios. Understanding the strengths and limitations of both helps you make smarter fuelling decisions rather than just reaching for whichever brand you've always used.
The Format Difference: Why It Matters
The most basic distinction β gel vs chew β creates cascading differences in nearly every aspect of how these products function during running.
GU Energy Gel is a thick, syrup-like gel consumed by squeezing an open foil packet. One full packet delivers 20β21g of carbohydrates in approximately 5β8 seconds of consumption. Recommended to be taken with 150β200ml of water at an aid station or from a carried flask.
Clif Shot Bloks are soft, pliable gummy cubes sold in a 60g package of six cubes. Standard serving is three cubes providing approximately 16.5g of carbohydrates. Consumed by chewing, at whatever pace you choose, over 15β30 seconds. Can be taken with or without water, though water remains advisable.
These aren't just aesthetic differences. The format affects absorption rate, GI stress, palatability over time, race-pace practicality, and how much you can carry. Almost every practical comparison between these two products traces back to this fundamental format distinction.
Carbohydrate Delivery: The Numbers
GU Energy Gel:
- 20β21g carbohydrates per packet
- One packet every 25β30 minutes = 40β50g/hour
- One packet every 20 minutes = 60g/hour (requires 3 gels/hour)
- Carbohydrate ratio: maltodextrin + fructose (2:1 ratio β traditional dual-source)
Clif Shot Bloks:
- 33g carbohydrates per full package (6 cubes)
- 16.5g per half package (3 cubes)
- One full package every 30 minutes = 66g/hour
- Half package every 15 minutes = 66g/hour (more gradual delivery)
- Carbohydrate sources: organic brown rice syrup (glucose dominant) and organic evaporated cane juice
The absorption rate question: Research comparing liquid gels and chewed solid carbohydrates at matched doses consistently finds no statistically significant difference in total carbohydrate oxidation rates during exercise at moderate intensity (60β75% VO2max). The format matters less than the dose and the consistency of intake.
What does differ is the delivery timeline. Liquid gels create a single bolus in the stomach that begins absorption quickly. Chewed Shot Bloks create smaller sequential carbohydrate deliveries as each cube is chewed and swallowed β a more gradual delivery profile.
At the absorption rates relevant to running, this difference is unlikely to be performance-significant for most athletes in most conditions. It becomes more relevant at very high intensities where gastric emptying is rate-limiting β at these intensities, gels' faster delivery may provide a fractional advantage.
GI Tolerance: Which Is Easier on the Stomach?
This is where the format difference creates its most meaningful practical distinction.
GU Energy Gel and osmotic stress: The concentrated carbohydrate solution in GU gels creates an osmotic gradient in the stomach β drawing water from surrounding tissue to equilibrate concentration. This osmotic "pull" is the primary mechanism behind sports nutrition GI distress: bloating, cramping, and nausea. GU mitigates this by recommending water intake alongside the gel, which dilutes the concentration and reduces osmotic stress.
Without water, GU gels create a significantly elevated osmotic challenge. With adequate water (150β200ml), the osmotic stress is substantially reduced for most athletes.
Clif Shot Bloks and gradual delivery: The chewing and swallowing process of Shot Bloks creates smaller, sequential carbohydrate boluses in the stomach rather than a single large dose. Smaller boluses create less osmotic stress per delivery event. The result for many GI-sensitive runners is noticeably better comfort with Shot Bloks than with conventional gels.
Additionally, Shot Bloks' absence of artificial sweeteners (they use organic cane sugar) and their simpler ingredient list may reduce the artificial additive load that contributes to GI irritation during running's constant mechanical jarring.
For GI-sensitive runners: Shot Bloks have the better GI tolerance track record. Many runners who consistently experience cramping or nausea with conventional gels find Shot Bloks considerably more manageable. This isn't universal β some runners prefer the speed of gel consumption and tolerate them well β but the trend in community experience is consistent.
Taste and Long-Run Palatability
GU Energy Gel flavour range: 25+ options including Salted Caramel, Chocolate Outrage, Tri Berry, Vanilla Bean, Strawberry Banana, and many others. The flavour intensity is higher than Shot Bloks β GU gels are noticeably sweet. Caffeinated options at 20mg, 40mg, and 100mg (Roctane) caffeine across multiple flavours.
Shot Bloks flavour range: Citrus, Watermelon, Strawberry, Tropical Punch, Margarita (with salt), Black Cherry (50mg caffeine), Mountain Berry (25mg caffeine). Flavour intensity is moderate β less sweet than GU, more refreshing in character.
Long-run palatability comparison: This is Shot Bloks' clearest advantage. The moderate sweetness and refreshing flavour profiles β particularly Watermelon and Margarita β maintain palatability significantly better than GU across 3+ hour efforts. GU's intense sweetness, enjoyable in the first hour, frequently becomes unpleasant by mile 20.
The Margarita Shot Blok (salted, lime-citrus) deserves particular mention β it's one of the most uniquely effective long-run nutrition products on the market. The salt-citrus combination is refreshing in a way that sweet gels simply cannot replicate, and the higher sodium content in the Margarita variety is a functional benefit for hot Australian conditions.
GU's advantage: The 25+ flavour range provides more variety and the intense sweetness is genuinely enjoyable early in a run. For races under 2.5 hours where flavour fatigue isn't a concern, GU's flavour range is a genuine asset.
Race-Pace Practicality
GU at race pace: Opening a GU packet, squeezing the contents, and disposing of the empty packet takes approximately 8β12 seconds. At a 4:30/km marathon pace, this represents roughly 50β65m of distracted running. Manageable with practice, but it's a practiced skill rather than a natural movement.
Shot Bloks at race pace: Opening the package, extracting cubes, and chewing while running takes 20β40 seconds. At marathon race pace, this is a more significant disruption β both the duration and the cognitive demand of chewing while maintaining form are higher than gel consumption.
Verdict for competitive road racing: GU's faster consumption time is a genuine practical advantage for runners competing at hard effort where any disruption to breathing or form is undesirable. For trail running and ultra events at lower intensities, Shot Bloks' slower pace of consumption is entirely manageable.
Carrying Capacity and Portability
GU: A standard GU packet measures approximately 10cm Γ 4cm when full β highly compact. Eight gel packets add minimal bulk and fit in most race shorts pockets, gel belts, and vest pockets. Easy to carry race-day supplies without a vest.
Shot Bloks: A Shot Bloks package is significantly larger β approximately 12cm Γ 8cm and thicker than a gel packet. For a 4-hour marathon at 60g/hour, you'd carry approximately 8 packages β substantial bulk. Best suited to running vest carrying rather than shorts pockets or gel belts.
Verdict: GU is dramatically more portable and better suited to minimalist race kit.
Caffeine Strategy Comparison
GU: 20mg (light), 40mg (standard), 100mg (Roctane) options across multiple flavours. The most granular caffeine management in the mainstream gel market. Runners can precisely time caffeine introduction and escalation across a race using GU's variety.
Shot Bloks: 25mg (Mountain Berry) or 50mg (Black Cherry) per three-cube serving. Fewer options but adequate for a late-race caffeine strategy. The 50mg dose from Black Cherry is a meaningful mid-race caffeine stimulus β take three cubes at the 75% mark of your race for a genuine fatigue-blunting effect.
Verdict: GU has more sophisticated caffeine management options, particularly valuable for experienced runners who manage caffeine periodisation carefully.
Price Comparison
GU Energy Gel: ~$3.00β$4.00 per gel (20g carbs)
- Cost per gram of carbohydrate: ~$0.15β$0.20
Clif Shot Bloks: ~$4.00β$5.50 per package (33g carbs)
- Cost per gram of carbohydrate: ~$0.12β$0.17
Shot Bloks offer slightly better value per gram of carbohydrate. The per-session cost comparison depends on your target hourly intake and which format you need more of to reach it.
Scenario Guide: Which to Use When
| Scenario | Better Choice | Reason |
|----------|--------------|---------|
| Road marathon, competitive | GU | Speed, portability, caffeine options |
| Hot summer long run | Shot Bloks Margarita | Sodium, refreshing flavour |
| Trail run 3β6 hours | Shot Bloks | Palatability, gradual intake |
| Ultra-marathon 6+ hours | Mix of both | Variety prevents fatigue |
| First-time gel user | GU | Ubiquitous at aid stations, familiar |
| GI-sensitive runner | Shot Bloks | Better tolerance |
| No vest/minimal kit | GU | Far more portable |
| Training run (any distance) | Either | Stakes are low, personal preference |
The Practical Answer: Use Both
The most effective long-run and race nutrition strategy for most runners involves having both products in rotation. GU for speed and portability in competitive road racing and shorter events; Shot Bloks for trail running, ultra-distance, and warm-weather running where palatability and gradual intake matter more than consumption speed.
Many experienced runners mix products within a single event β GU for the first half, Shot Bloks for variety in the second half. This rotation addresses flavour fatigue while maintaining practical consumption speed where it matters most.
GU Energy Gel: 7.5/10 β Best for competition, portability, and caffeine management
Clif Shot Bloks: 7.5/10 β Best for GI tolerance, long-run palatability, and trail running
Tied overall β but for genuinely different use cases. Understanding which scenario fits which product is more valuable than picking an absolute winner.
Prices quoted are approximate AUD as of 2026. Both products available at iHerb AU and major Australian running retailers.
Mixing Products Within a Race: The Hybrid Strategy
The most experienced endurance runners in Australia don't typically commit exclusively to one product for an entire race. The hybrid approach β using both GU and Shot Bloks at different phases β captures the best characteristics of each:
First half of race (GU dominant): GU's fast consumption speed and precise gel scheduling suit the higher-intensity, more focused first half of a marathon or trail race. Take GU at 20β25 minute intervals, maintaining a consistent carbohydrate delivery rate without the slowing effect of chewing at high effort.
Second half (Shot Bloks introduced): From the 60β70% mark of a long event, rotate Shot Bloks into your fuelling rotation. The flavour variety breaks the GU sweetness pattern, the chewable texture provides psychological variety, and the slower consumption pace is more manageable as fatigue accumulates.
For ultra events (Shot Bloks primary): From the 3-hour mark onward of an ultra, Shot Bloks' palatability advantage becomes decisive. Make them your primary fuel for lower-intensity hiking and easier sections, supplementing with GU only during higher-intensity running sections where speed of consumption matters.
This hybrid approach is used by thousands of Australian endurance runners and addresses the main weakness of each product individually β GU's flavour fatigue and Shot Bloks' consumption speed.
Aid Station Strategy for Each Product
Using GU at Australian aid station events:
Most Australian road running events stock GU at aid stations β it's the most widely distributed gel brand nationally. This means you can use fewer GU gels from your own supply and pick up additional gels at aid stations, reducing what you carry. Confirm in advance what gels your specific race provides so you can train with the exact product on course.
Using Shot Bloks at events:
Shot Bloks are less commonly stocked at Australian race aid stations. For events where you want to use Shot Bloks, plan to carry your full race-day supply. Account for the larger package size in your kit selection β a running vest or hydration belt is essentially mandatory for carrying more than two packages of Shot Bloks.
Environmental Considerations
Both GU and Clif Shot Bloks produce packaging waste β foil and plastic sachets that must be disposed of correctly during racing. Most Australian race events provide gel/wrapper bins at aid stations. Littering gel packaging on course is both environmentally irresponsible and a rules violation at many events.
GU produces smaller packaging per serving than Shot Bloks, which creates a slightly lower waste footprint per gram of carbohydrate. Both brands have made some commitments to sustainable packaging development, though fully compostable gel packaging remains an industry challenge in 2026.
Clif Bar Company (Shot Bloks' parent brand) has a broader environmental sustainability program than most sports nutrition companies, which factors into some runners' purchasing decisions.
Final Recommendation
The answer to "GU or Shot Bloks?" is almost always "it depends" β and that's a genuinely useful answer when you understand what it depends on.
For road marathon racing and shorter events: GU, for its speed, portability, and event availability.
For trail running, ultra events, and heat: Shot Bloks β especially the Margarita variety β for palatability, gradual intake, and sodium content.
For runners with GI sensitivity: Shot Bloks' gradual delivery and cleaner ingredient profile tend to outperform.
For runners who want variety: Use both in rotation.
Neither is wrong. Both will fuel your training and racing competently. The optimal choice is the one that best matches your specific race demands and personal tolerance.
Final Ratings: GU Energy Gel 7.5/10 | Clif Shot Bloks 7.5/10
Prices quoted approximate AUD as of 2026. Both available at iHerb AU, Amazon AU, and major Australian running retailers.
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