Running twice a day, a practice runners call “doubles,” involves splitting the day’s total mileage into two separate sessions, typically morning and evening. While common among elite athletes, the average runner can also benefit if the approach is structured correctly. Mismanagement of this increased training load, however, can quickly lead to fatigue, injury, and a decline in performance. Successfully incorporating doubles relies on understanding the physiological and logistical reasons for the practice.
Why Runners Choose Twice-Daily Sessions
The primary motivation for running doubles is the ability to increase weekly training volume without placing excessive strain on the body in a single session. Two shorter runs generally impose less orthopedic stress on the joints and connective tissues than one long effort of the same total distance. This strategy allows experienced runners to accumulate higher mileage, which is directly linked to improved aerobic endurance and performance, especially in longer distance events.
A short, easy second run acts as a form of active recovery, increasing blood flow to the tired muscles. This helps flush out stiffness and deliver necessary nutrients for repair. Performing a second run when glycogen stores are partially depleted can also stimulate specific cellular adaptations, making the body more efficient at utilizing fat for fuel. For runners with busy schedules, dividing a 60- to 90-minute run into two shorter sessions often makes it logistically easier to fit training around work and family commitments.
Recognizing the Signs of Overtraining
Pushing the body too far without adequate rest can lead to Overtraining Syndrome (OTS), resulting from an imbalance between training stress and recovery. A key physical indicator is a chronically elevated resting heart rate (RHR), where a sustained rise of 5 to 10 beats per minute above baseline signals failed recovery. Persistent muscle soreness lasting more than 48 hours, or heavy, sluggish legs that do not feel refreshed, are clear physical red flags.
The immune system also suffers under chronic stress, often manifesting as a greater frequency of colds or recurrent minor infections. Psychological indicators include significant mood changes, increased irritability, and a profound loss of motivation for running. Sleep disturbances, such as restless or unrefreshing sleep despite physical exhaustion, are also common symptoms. Chronic, excessive training can elevate cortisol levels, which interferes with the body’s ability to repair muscle tissue.
Guidelines for Safe and Effective Double Runs
Base and Pace
Implementing double runs safely requires a strategic approach, beginning with a solid base of running experience. Runners should typically have a consistent foundation of high weekly mileage, often 40 miles per week or more, before introducing a second daily session. When adding a double, the second run should almost always be performed at an easy, recovery pace. This run serves primarily to stimulate blood flow and recovery rather than to impose significant additional stress.
Timing and Recovery
The timing between the two sessions is a critical factor for maximizing recovery and adaptation. It is recommended to allow a minimum of 6 to 8 hours between runs to provide the body with sufficient time to initiate glycogen restoration and muscular repair. Scheduling the second run too soon means the body may not replenish energy stores adequately, which compromises the quality of the second run and increases overall fatigue.
Nutrition Strategy
Prioritizing nutrition is paramount when running twice a day due to the compressed recovery window. After the first run, especially a hard session, immediate intake of carbohydrates and protein is necessary to jump-start the replenishment of muscle glycogen stores. Consuming approximately 50 grams of carbohydrate per hour for the first few hours can significantly boost the rate of glycogen storage, which is necessary to fuel the second session. Gradually introducing doubles, perhaps starting with only one or two days per week, allows the body time to adapt to the increased frequency of training.