Gear Shift Cardio Gets Scientific

"Gear shifting" workouts, which intentionally vary pace, train the body to adapt to different energy systems and efforts within a single session. This method improves the body's efficiency at clearing lactic acid and can help runners sustain harder paces for longer periods. The two paces in the "gear shift" workout serve different physiological purposes. The "steady" run builds a foundational aerobic base, while the slightly faster marathon pace improves lactate threshold, which is the body's ability to sustain higher intensity exercise. Training with these paces helps simulate the fatigue experienced at the end of a race. The coach mentioned, David Abbott, is an online running coach who reportedly started running at age 35 and qualified for the Boston Marathon a year later. His training philosophy often emphasizes building a strong aerobic base with slower miles to avoid injury. New research shows that as runners fatigue, the neuromuscular system adjusts muscle activation to prioritize stability. A February 2026 study found that under fatigue, activation increases in the quadriceps and glutes during the stance phase and in the tibialis anterior (the main shin muscle) during the swing phase to stiffen the ankle. These fatigue-related changes in muscle function are directly linked to injury risk. For example, studies have demonstrated that fatigue can lead to reduced activation of the biceps femoris, a key hamstring muscle, during the late swing phase of a runner's stride, which may increase the likelihood of muscle strains. Interval training is a proven method for boosting both speed and endurance. The alternating periods of high and low intensity strengthen the cardiovascular system and train muscles to recover more efficiently from hard efforts.