The Role of the Long Run
The long run has always been a pillar of endurance training. It builds aerobic capacity, muscular endurance, and mental toughness. For marathoners, this often means running between 18 to 22 miles. Half marathoners typically aim for 10 to 14 miles. But these numbers don’t tell the whole story—especially for triathletes.
In single-sport running, the long run generally makes up about 25 to 30 percent of weekly mileage. That guideline comes from research like Smyth et al. (2019), which emphasizes gradual adaptation. For triathletes, though, that same approach doesn’t always translate. Long runs must be balanced with swim and bike volume. Going too long on foot can take away from quality efforts in the other disciplines.
Many elite triathletes keep long runs within a 90 to 120-minute window. That allows for strong run development without compromising recovery. Studies like Foster et al. (2022) support the idea that aerobic conditioning can be built across modalities. And while traditional marathon plans often stretch runs beyond two hours, some research questions whether those extra miles add value or simply increase injury risk. Midgley et al. (2007) and Seiler (2010) argue that the consistency of weekly volume matters more than any single long effort.
Splitting Long Runs: Useful or Overrated?
Splitting a long run into two shorter sessions in the same day can be a strategic way to increase volume without overloading the body. It’s often used by masters athletes, those managing injury, or anyone easing into higher mileage.
However, continuous runs offer unique physiological benefits. They challenge the body to store and use glycogen more efficiently, increase fat oxidation, and improve fatigue resistance over time. These adaptations are harder to achieve with segmented efforts. Trehearn and Buresh (2020) highlight this difference, emphasizing the role of sustained effort in aerobic development.
Still, split sessions have their place. Noble and Howatson (2021) found that they can help athletes build volume with less risk of overuse injury. When used intentionally, they’re a great tool. They just aren’t a replacement for the true long run when race specificity matters.
Why Triathletes Don’t Always Need the Big Long Run
Triathletes have a different equation to solve. Because cycling provides a high-volume aerobic load with low impact, it can enhance endurance without the wear and tear of running. Hausswirth and Lehénaff (2001) showed that cycling improves VO₂max and running economy, especially when integrated into off-season or base training.
Long aerobic bike rides can substitute for some of the benefits of a long run. For this reason, many triathletes keep their longest runs under two hours and use back-to-back ride and run combinations to simulate race-day fatigue.
It’s not about skipping the long run. It’s about using it wisely within the full context of triathlon training.
Daily Running vs. Every Other Day
There’s ongoing debate over how often to run. Some athletes thrive on daily mileage, while others make better progress running every other day and using cross-training in between.
The key is matching frequency with recovery capacity. Mujika et al. (2018) noted that experienced, high-mileage athletes benefit from daily running when intensity and terrain are well-managed. But alternating running days with swimming or cycling can produce similar aerobic gains, with less injury risk. Nielsen et al. (2014) found that cross-training preserves fitness and reduces stress-related injuries, especially useful for age-group athletes juggling busy schedules.
Ultimately, there's no universal answer. It comes down to how well your body responds, and how well your plan is structured.
Key Takeaways for Endurance Athletes
• Long runs are important but don’t need to be extreme: Marathoners often aim for 18 to 22 miles. Triathletes typically benefit from 90 to 120 minutes, especially when combined with bike volume.
• Split runs can build volume strategically: While they don’t provide the same physiological adaptations as continuous long runs, they’re useful for injury prevention and gradual progression.
• Cross-training supports endurance and recovery: Cycling and swimming offer aerobic benefits while reducing impact, helping athletes train consistently without overuse.
• Training frequency should match recovery capacity: Daily running works for experienced athletes with strong recovery habits. Alternating running with cross-training can reduce injury risk and maintain fitness.
• There’s no universal formula: The best approach is individualized, based on your goals, training history, and how your body responds across disciplines.
Ready to Level Up Your Long Run Strategy?
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