The impact of a long training run on muscle damage and running economy in runners training for a marathon

The purposes of this study were to evaluate whether there were changes in markers of cardiovascular and muscle damage and then to determine whether running economy (RE) was adversely affected due to those changes in a group of runners training for a marathon following a 26-km moderately paced outdoor long training run (LTR). Fifteen, healthy male participants (age: 35.2 ± 11.1 years; height = 171.2 ± 14.5 cm; body mass = 73.6 ± 11.9 kg; and VO2max = 63.6 ± 12.7 mL/kg/minute) completed the protocol. The LTR consisted of a 26-km run on a marked outdoor course with water stops and heart rate (HR) and rating of perceived exertion checkpoints every 5 km. Muscle damage [serum creatine kinase (CK)], delayed onset muscle soreness (DOMS), cardiorespiratory measures (HR, pulmonary ventilation, respiratory exchange ratio), muscle power, step rate (SR), and RE (oxygen consumption during treadmill running at 3.1, 3.6, and 4.0 m/second) were assessed before and 24, 48, and 72 hours after exercise. A repeated-measures analysis of variance showed that serum CK levels were significantly elevated at 24, 48, and 72 hours (145%, 112%, and 72% increase above baseline, respectively; p < 0.05). However, these significant increases in serum CK were not associated with an increase in DOMS. In addition, none of the RE measures or other dependent variables showed changes during the study. It was concluded that the muscle damage caused by a 26-km LTR was not reflected by changes in RE at submaximal speeds. Therefore, an LTR of this duration and intensity can be well tolerated in participants training for a marathon and routine training can be followed in the days after this run with few adverse consequences.