Running: Why Runners Incorporate Double Training Sessions

Why do runners do doubles?

Runners often incorporate "doubles"—two distinct training sessions within a single day—primarily to increase overall training volume, enhance physiological adaptations, and optimize recovery without excessively long individual runs.

Understanding "Doubles" in Running

In the context of running, a "double" refers to the practice of completing two separate running workouts on the same day, typically separated by several hours. This strategy is distinct from a single, continuous long run, even if the total mileage for the day is similar. The rationale behind splitting a day's training volume into two sessions is rooted in both physiological benefits and practical considerations for athletes aiming to maximize performance and adaptation.

The Primary Benefits of Double Training Sessions

The decision to implement double runs is not arbitrary; it's a strategic choice made to leverage specific advantages:

• Increased Training Volume: For runners training for marathons, ultra-marathons, or competitive distances, a high weekly mileage is often necessary. Doubles allow athletes to accumulate more miles without making individual runs excessively long, which can reduce the risk of overuse injuries and excessive fatigue from a single, prolonged effort.
• Enhanced Recovery and Reduced Injury Risk: Splitting a long run into two shorter ones can be less taxing on the musculoskeletal system. The body gets a brief recovery period between sessions, allowing for some repair and replenishment, which can mitigate cumulative fatigue and lower the acute risk of injury compared to a single, very long run.
• Optimized Physiological Adaptations:
  • Glycogen Depletion and Fat Utilization: A common strategy involves performing the second run of the day with partially depleted glycogen stores from the first run. This "train low" approach can enhance the body's ability to utilize fat as a fuel source, improving metabolic efficiency for endurance events.
  • Mitochondrial Biogenesis: Frequent, shorter bouts of exercise can stimulate mitochondrial growth and efficiency more effectively than fewer, longer sessions for some athletes. Mitochondria are the "powerhouses" of cells, crucial for aerobic energy production.
  • Hormonal Response: Shorter, more frequent stimuli can lead to a more sustained elevation of beneficial training hormones without crossing into overtraining plateaus that might occur with excessively long single sessions.
• Improved Time Management: For athletes with demanding schedules, it can be easier to fit two shorter runs into a day (e.g., morning and evening) than one very long run, providing flexibility and consistency in training.
• Mental Freshness: Breaking up the mileage can make the training process feel less daunting. Mentally, two 45-minute runs can be more approachable and sustainable than a single 90-minute run, helping maintain motivation.

Physiological Adaptations and Scientific Rationale

The scientific basis for doubles centers on how the body responds to repeated, spaced stimuli:

• Cumulative Training Load: The total training impulse over a 24-hour period can be higher with doubles, but the stress per session is lower. This allows for a greater overall adaptive stimulus without overwhelming the body's acute recovery capacity.
• Aerobic System Enhancement: By providing multiple opportunities for the cardiovascular system to be engaged, doubles can lead to improvements in VO2 max, cardiac output, and capillarization (the growth of new blood vessels), all vital for endurance performance.
• Neuromuscular Efficiency: Shorter runs can allow for more consistent practice of efficient running mechanics when the body is less fatigued, reinforcing good form.

Strategic Implementation of Doubles

Doubles are not a one-size-fits-all solution and require careful planning:

• Types of Doubles:
  • Easy-Easy: Two easy-paced runs, often used to accumulate volume without high intensity.
  • Workout-Easy: A harder workout (e.g., tempo, intervals) followed by an easy recovery run later in the day. The recovery run aids in blood flow and waste product removal.
  • Easy-Workout: Less common, but sometimes an easy morning run is followed by an evening workout, allowing for full recovery from the morning session.
• Timing: Allow sufficient recovery time between runs, typically 4-8 hours. This allows for some physiological recovery, including partial glycogen replenishment and reduction of muscle soreness.
• Nutrition and Hydration: Proper fueling between sessions is crucial to facilitate recovery and ensure adequate energy for the second run. Emphasis should be on carbohydrates for glycogen replenishment and protein for muscle repair.
• Listen to Your Body: Doubles increase overall training stress. It's vital to monitor fatigue levels, sleep quality, and any signs of overtraining. Not every runner can or should implement doubles.

Considerations and Potential Drawbacks

While beneficial, doubles also come with challenges:

• Increased Overtraining Risk: Without proper management, the cumulative stress of doubles can lead to overtraining, burnout, and increased susceptibility to illness or injury.
• Fatigue Management: Even with shorter individual runs, the total daily mileage can be draining, requiring excellent sleep hygiene and recovery strategies.
• Logistical Demands: Fitting two runs into a day can be challenging for those with work, family, or social commitments.
• No Substitute for Long Runs: While doubles add volume, they don't fully replicate the specific physiological and mental demands of a single, very long run, which is crucial for marathon and ultra-marathon preparation. Long runs still need to be a component of training.

Who Benefits Most from Doubles?

Doubles are typically employed by:

• Elite and High-Volume Runners: Athletes accumulating 70+ miles per week often find doubles essential for managing volume and recovery.
• Marathon and Ultra-Marathon Trainees: Those preparing for endurance events that demand high mileage.
• Runners with Specific Time Constraints: Individuals who cannot dedicate a single large block of time but can fit in two shorter sessions.
• Athletes Seeking Specific Adaptations: Those intentionally using the "train low" strategy for metabolic benefits.

Conclusion: Optimizing Your Training Strategy

The practice of incorporating "doubles" into a running regimen is a sophisticated training strategy employed by athletes seeking to optimize performance, manage training load, and enhance specific physiological adaptations. By strategically splitting daily mileage, runners can accumulate higher volumes, potentially reduce injury risk, and improve metabolic efficiency. However, doubles are not universally necessary or beneficial for all runners. Successful implementation requires careful planning, meticulous attention to recovery, and a deep understanding of one's own physiological responses to avoid the pitfalls of overtraining. As with any advanced training technique, consultation with a qualified coach or exercise professional is recommended to determine if doubles align with individual goals and current fitness levels.