947 Journal of Strength and Conditioning Research, 2006, 20(4), 947–954  2006 National Strength & Conditioning Association SHORT-TERM PLYOMETRIC TRAINING IMPROVES RUNNING ECONOMY IN HIGHLY TRAINED MIDDLE AND LONG DISTANCE RUNNERS PHILO U. SAUNDERS, 1,4 RICHARD D. TELFORD, 2 DAVID B. PYNE, 1 ESA M. PELTOLA, 1,2 ROSS B. CUNNINGHAM, 3 CHRIS J. GORE, 1 AND JOHN A. HAWLEY 4 1 Department of Physiology, Australian Institute of Sport, Belconnen, Australia; 2 Track and Field Program, Australian Institute of Sport, Belconnen, Australia; 3 Statwise Pty. Ltd., Flynn, Australia; 4 Exercise Metabolism Group, School of Medical Sciences, RMIT University, Bundoora, Australia. ABSTRACT. Saunders, P.U., R.D. Telford, D.B. Pyne, E.M. Pel- tola, R.B. Cunningham, C.J. Gore, and J.A. Hawley. Short-term plyometric training improves running economy in highly trained middle and long distance runners. J. Strength Cond. Res. 20(4): 947–954. 2006.—Fifteen highly trained distance runners (V ˙ O 2 max 71.1  6.0 ml·min -1 ·kg -1 , mean  SD) were randomly assigned to a plyometric training (PLY; n = 7) or control (CON; n = 8) group. In addition to their normal training, the PLY group undertook 3  30 minutes PLY sessions per week for 9 weeks. Running economy (RE) was assessed during 3  4 min- ute treadmill runs (14, 16, and 18 km·h -1 ), followed by an incre- mental test to measure V ˙ O 2 max. Muscle power characteristics were assessed on a portable, unidirectional ground reaction force plate. Compared with CON, PLY improved RE at 18 km·h -1 (4.1%, p = 0.02), but not at 14 or 16 km·h -1 . This was accom- panied by trends for increased average power during a 5-jump plyometric test (15%, p = 0.11), a shorter time to reach maximal dynamic strength during a strength quality assessment test (14%, p = 0.09), and a lower V ˙ O 2 -speed slope (14%, p = 0.12) after 9 weeks of PLY. There were no significant differences in cardiorespiratory measures or V ˙ O 2 max as a result of PLY. In a group of highly-trained distance runners, 9 weeks of PLY im- proved RE, with likely mechanisms residing in the muscle, or alternatively by improving running mechanics. KEY WORDS. oxygen consumption, strength training, elite run- ners INTRODUCTION I n highly-trained runners, there are a number of physiological factors that determine running performance, with running economy (RE) iden- tified as a critical factor in distance running performance (28). RE is represented by the en- ergy expenditure and expressed as the submaximal O 2 consumption (V ˙ O 2 submax) at a given running speed (2, 7, 8, 24). Runners with good RE use less O 2 than runners with poor RE at the same steady-state speed (9–11). The relationship between RE and performance is well docu- mented, with many independent reports demonstrating a strong relationship between these 2 variables (7–10, 12, 26). Accordingly, it is likely that any improvement in RE will be associated with improved distance running per- formance. Better RE coincides with a lower O 2 cost at a given running speed. Submaximal O 2 consumption is used as an indicator of RE (2, 7, 8, 24) on the assumption of negligible anaerobic contribution associated with sub- maximal running speeds. Runners with good RE use less O 2 than runners with poor RE at the same steady-state speed (33). Given the importance of RE in performance, successful training interventions that improve RE would be advantageous for the athlete. We have recently reported improved RE in elite run- ners after 20 days of moderate simulated altitude expo- sure (30). However, many countries may not have appro- priate training venues/facilities at altitude, and the use of simulated altitude houses or chambers is even more impractical for most nations. Accordingly, if alternative training techniques can improve RE, they would likely be embraced by coaches and athletes. One such approach is to supplement normal running training with strength/re- sistance training. Such training has previously been shown to improve RE (20, 23, 25, 31, 34). Specific types of strength training can improve anaerobic power char- acteristics, such as the ability to produce short contact times and faster force production (3, 19). Heavy resis- tance training (e.g., full squats) has been reported to im- prove endurance performance in previously untrained subjects (16, 21, 22), and RE in moderately-trained fe- male distance runners, without concomitant changes in V ˙ O 2 max (20). Recent work has shown that a combination of heavy-weight training and endurance training also leads to improved running performance and enhanced RE in well-trained triathletes (23). A specific type of strength training, known as explo- sive-strength training or plyometric training (PLY), has been reported to invoke specific neural adaptations such as increased activation of the motor units, with less mus- cle hypertrophy than typically observed after heavy-re- sistance strength training (14, 15, 27). PLY enhances the muscle’s ability to generate power by exaggerating the stretch-shorten cycle, using activities such as bounding, jumping, and hopping (34). PLY also has the potential to increase the stiffness of the muscle-tendon system, which allows the body to store and utilize elastic energy more effectively (31). Both of these adaptations resulting from PLY could potentially improve RE by generating greater force production from the muscles without a proportion- ate increase in the metabolic energy requirement. In this regard, Paavolainen et al. (25) reported that in moder- ately trained runners, 9 weeks of PLY improved RE (8.1%) and 5-km performance (3.1%) with no changes in V ˙ O 2 max. Similarly, other studies have also shown im- provements in RE and performance with no change in V ˙ O 2 max after short-term PLY in moderately-trained sub- jects (31, 34). To date, however, there is little research investigating the effects of PLY in highly trained distance