Changes in muscle power and neuromuscular efficiency after a 40-minute downhill run in veteran long distance runners

Objective: To establish whether there was a relationship between the total accumulated distances of racing in veteran runners and the neuromuscular ef ficiency of the quadriceps muscles before and after a downhill run. Setting: University of Cape Town, Sports Science Institute of South Africa. Participants: Twenty male veteran long distance runners (45-50 years of age ) with a range of training (1,300 km to 111,280 km) and racing (0 km to 9,7 37 km) experience. Intervention: A 40-minute downhill run (-10% decline) on a treadmill. at a speed corresponding to 70% of the subject's peak treadmill running speed. Main Outcome Measures: The difference between integrated electromyography ( IEMG)/mean force over a 5 s maximal voluntary isometric contraction before and after the downhill run was calculated as the delta (Delta) neuromuscula r efficiency. This was related to the total kilometers trained, current tra ining distance, total kilometers raced, and number of races > 56 km. The di fference in drop jump height before and after the downhill run was measured as well as changes in heart rate throughout the run. Results: There was a significant curvilinear relationship between the Delta neuromuscular efficiency and total kilometers raced (R-2 = 0.53, p < 0.05) , and a significant inverse relationship between Delta neuromuscular effici ency and the number of races > 56 km (r = -0.50, p < 0.05). Drop jump heigh t decreased after the downhill run, and heart rate increased during the run . Conclusions: Runners who have raced an accumulated distance of > 5,000 km s how a significant dissociation in the Delta neuromuscular efficiency after a downhill run, compared with less experienced runners. Although possible c auses for the dissociation are discussed, further research is needed.