The Science Behind SIS Isotonic Gels
Unlike traditional energy gels that have a high concentration of carbohydrates (hypertonic), Science in Sport (SIS) pioneered the isotonic formula. The term 'isotonic' means the gel's concentration is similar to the body's own fluids. This key difference has a significant impact on how the gel is absorbed and digested during exercise.
When a runner or cyclist consumes a hypertonic gel, the body must draw water from surrounding cells into the stomach to dilute the high sugar concentration before it can be effectively absorbed. This process can be slow and often leads to the dreaded 'sloshy' stomach, bloating, or other gastrointestinal (GI) issues. The isotonic nature of SIS gels means this dilution step is not required, allowing the carbohydrates to pass through the stomach and into the small intestine much more quickly.
The primary carbohydrate source in the standard SIS GO Isotonic gels is maltodextrin, derived from maize. Maltodextrin is a complex carbohydrate that requires less water to digest than simple sugars like fructose, which also helps speed up absorption. For athletes with sensitive stomachs or those who struggle to consume thick, sugary gels, this watery, less concentrated formula is a significant advantage.
A Look at the Different SIS Gel Formulations
SIS has developed a range of gels to meet different fueling needs. While the core GO Isotonic gel is their most well-known product, others offer targeted benefits for specific situations.
GO Isotonic Energy Gels
This is the flagship product, designed for quick, consistent energy delivery during any endurance exercise lasting over 90 minutes. Each gel provides 22 grams of carbohydrates and is formulated for easy digestion without extra water. It's a reliable choice for beginners getting used to race-day nutrition.
GO Energy + Electrolyte
This variant combines the fast-absorbing carbs of the isotonic gel with added electrolytes like sodium, potassium, and magnesium. It's particularly useful for activities in hot weather or when sweating heavily, helping to replace lost minerals and prevent cramping. The addition of electrolytes increases the gel's tonicity, meaning it is no longer strictly isotonic, but still easier to stomach than many traditional gels.
GO Energy + Caffeine
For a mental and physical boost, SIS offers gels with added caffeine, available in both 75mg and 150mg concentrations. Caffeine is known to reduce the perception of fatigue and increase alertness, which can be beneficial in the later stages of a long race or before a particularly tough segment. It should be used strategically and trialed in training to ensure individual tolerance.
Beta Fuel Dual Source Energy Gel
Developed for elite endurance athletes, the Beta Fuel gel contains a higher 40g dose of carbohydrates from a dual source (maltodextrin and fructose) in a 1:0.8 ratio. This specific blend allows the body to absorb more carbohydrates per hour, increasing power output and fuel efficiency for efforts lasting over two hours. Unlike the GO isotonic gels, Beta Fuel is more concentrated and may not be suitable for those with untrained stomachs or beginners.
Potential Downsides and Considerations
Despite the benefits, SIS gels are not without their potential drawbacks. The most common point of contention is the packaging size. Due to the high water content required for the isotonic formula, the sachets are noticeably larger than many competitor gels. For athletes with limited storage space in running belts or cycling jersey pockets, this can be an inconvenience. Additionally, because each standard gel contains fewer carbs (22g) per unit compared to some thicker gels, athletes need to carry and consume more gels to hit higher hourly carbohydrate targets.
Another important aspect is individual digestive tolerance. While the isotonic formula significantly reduces the risk of GI distress, some individuals may still experience issues, especially at high-intensity efforts or if they haven't trained their gut properly. It is crucial for any athlete to test their nutrition strategy during training, not on race day, to see what works best for their body.
Comparison: SIS Isotonic vs. Traditional Energy Gels
| Feature | SIS GO Isotonic Gels | Traditional Energy Gels (e.g., GU, Hammer) |
|---|---|---|
| Carbohydrate Source | Primarily Maltodextrin | Often a mix of maltodextrin, glucose, and fructose |
| Carbohydrate Concentration | Lower (Isotonic) | Higher (Hypertonic) |
| Water Required | No extra water needed | Must be consumed with water for optimal absorption |
| Stomach Comfort | Gentle on the stomach; minimizes bloating | Higher risk of GI distress, bloating, and cramping if not taken with water |
| Absorption Speed | Rapid due to isotonic formula | Slower; body must dilute gel before absorption |
| Gel Consistency | Watery, thinner, more like a sports drink | Thick, syrupy, or sticky texture |
| Carbohydrates per Gel | 22g (standard GO) | Varies; often 25g or more |
| Package Size | Larger due to higher water content | Smaller and more compact |
How to Use SIS Gels for Optimal Performance
Using SIS gels correctly is key to their effectiveness. Science in Sport recommends a strategic approach for maximizing fuel intake during prolonged exercise.
- For endurance events over 90 minutes: Aim for 60-90 grams of carbohydrates per hour. This can be achieved by consuming one GO Isotonic gel every 20-30 minutes. Combine with other SIS products or solid food to meet higher targets.
- For shorter, high-intensity workouts: Take a gel 15 minutes before starting to top off glycogen stores.
- For hot weather or heavy sweating: Incorporate the GO Energy + Electrolyte gels into your fueling plan to replenish lost minerals and maintain hydration balance.
- For a caffeine boost: Use a caffeinated gel in the later stages of a race or before a demanding climb to increase focus and reduce perceived effort.
For a detailed breakdown of which gel to use when, consult the official guide SIS Which Gel & When Guide.
Conclusion: So, do SIS energy gels work?
The answer is a definitive yes, SIS energy gels work, and their effectiveness is supported by both scientific principles and widespread athlete use. The unique isotonic formulation provides a distinct advantage by delivering rapid, easy-to-digest energy without the stomach upset often caused by thicker, hypertonic gels. This makes them a highly reliable and popular choice, particularly for those with sensitive stomachs or for use during long-duration, intense efforts where GI issues are common.
However, it's crucial to understand that not all gels are created equal, and individual needs differ. While the standard GO Isotonic gels are excellent for consistent, gentle fueling, options like the Beta Fuel are tailored for high-carb intake and specific race scenarios. The larger packaging and lower carbohydrate density per sachet are trade-offs for the isotonic benefit, but for many, the improved comfort and performance are worth it. By testing different SIS gels in training and developing a proper fueling strategy, athletes can confidently use them to enhance performance, delay fatigue, and avoid hitting the wall.
