Introduction ! It has been traditionally suggested that endur- ance performance, such as distance running, is determined by maximal oxygen uptake (V ˙ O 2max ), fractional utilization of V ˙ O 2max and running economy [3]. Athletes with similar V ˙ O 2max may have different running economy and endurance running performance can vary considerably [7, 27]. There is also evidence that anaerobic work capacity may influence considerably running performance in well-trained distance runners [6]. In addition, Noakes [25] has suggested that in elite athletes muscle power factors affected by an interaction of neuromuscular and anaero- bic characteristics may limit endurance perfor- mance and may be better predictors of success than V ˙ O 2max . Thus, it might be beneficial also for endurance runners to improve their neuromus- cular and anaerobic characteristics. Specific explosive type strength training (with low load but high action velocities) leads mainly to neural adaptations (e.g. increased rate of neu- ral activation of motor units) where as muscle hy- pertrophy will remain smaller than during typi- cal heavy resistance training [14,16, 31]. This might be beneficial for distance running per- formance, since an increased body mass is not de- sirable as athletes need to transport this higher body mass. Some recent studies [32, 33] have also demonstrated benefits of plyometric training on distance running performance. It has been shown that strength/plyometric training improves run- ning economy in runners [19, 22, 27, 32, 33], although the exact mechanism why this occurs is still unclear. It has been suggested that plyo- metric training improves musculotendinous stiff- ness resulting in better running economy and performance, because more stiff muscles are able to store and utilize elastic energy better during the ground contact [32]. On the contrary, Turner et al. [33] did not found any improvements in ca- pabilities that would have indicated improved ability to store and utilize elastic energy. Paavo- lainen et al. [27] postulated that explosive strength training had a positive influence on run- ning economy and running performance due to improved neuromuscular characteristics in en- durance athletes. However, it has been suggested that concurrent endurance and strength training Abstract ! To study effects of concurrent explosive strength and endurance training on aerobic and anaerobic performance and neuromuscular characteristics, 13 experimental (E) and 12 control (C) young (16 –18 years) distance runners trained for eight weeks with the same total training volume but 19% of the endurance training in E was replaced by explosive training. Maximal speed of maximal anaerobic running test and 30-m speed improved in E by 3.0 ± 2.0% (p < 0.01) and by 1.1 ± 1.3% (p < 0.05), respectively. Maximal speed of aerobic running test, maximal oxygen uptake and run- ning economy remained unchanged in both groups. Concentric and isometric leg extension forces increased in E but not in C. E also improved (p < 0.05) force-time characteristics accompanied by increased (p < 0.05) rapid neural activation of the muscles. The thickness of quadriceps femoris increased in E by 3.9 ± 4.7% (p < 0.01) and in C by 1.9 ± 2.0% (p < 0.05). The concurrent explosive strength and endurance training improved anaer- obic and selective neuromuscular performance characteristics in young distance runners with- out decreases in aerobic capacity, although al- most 20% of the total training volume was re- placed by explosive strength training for eight weeks. The neuromuscular improvements could be explained primarily by neural adaptations. Concurrent Endurance and Explosive Type Strength Training Improves Neuromuscular and Anaerobic Characteristics in Young Distance Runners Authors J. Mikkola 1 , H. Rusko 2 , A. Nummela 1 , T. Pollari 2 , K. Häkkinen 2 Affiliations 1 Department of Physiology, Research Institute for Olympic Sports, Jyväskylä, Finland 2 Department of Biology of Physical Activity and Neuromuscular Research Center, University of Jyväskylä, Jyväskylä, Finland Key words l " postpubertal endurance athlete l " rapid force production l " cardiovascular adaptation l " neural adaptation accepted after revision June 12, 2006 Bibliography DOI 10.1055/s-2007-964849 Published online 2007 Int J Sports Med © Georg Thie- me Verlag KG Stuttgart • New York • ISSN 0172-4622 Correspondence Jussi Mikkola, M.Sc. Department of Physiology Research Institute for Olympic Sports Rautpohjankatu 6 40700 Jyväskylä Finland jussi.mikkola@kihu.fi Mikkola J et al. Explosive Type Strength Training in Young Distance Runners… Int J Sports Med Training & Testing