682 Journal of Strength and Conditioning Research, 2006, 20(3), 682–688  2006 National Strength & Conditioning Association ROLE OF ENERGY SYSTEMS IN TWO INTERMITTENT FIELD TESTS IN WOMEN FIELD HOCKEY PLAYERS KOEN A.P.M. LEMMINK AND SUSAN H. VISSCHER Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen, The Netherlands. ABSTRACT. Lemmink, K.A.P.M., and S.H. Visscher. Role of en- ergy systems in two intermittent field tests in women field hock- ey players. J. Strength Cond. Res. 20(3):682–688. 2006.—The en- ergetics of 2 field tests that reflect physical performance in in- termittent sports (i.e., the Interval Shuttle Sprint Test [ISST] and the Interval Shuttle Run Test [ISRT]) were examined in 21 women field hockey players. The ISST required the players to perform 10 shuttle sprints starting every 20 seconds. During the ISRT, players alternately ran 20-m shuttles for 30 seconds and walked for 15 seconds with increasing speed. Anaerobic and aer- obic power tests included Wingate cycle sprints and a V ˙ O 2 max cycle test, respectively. Based on correlation and regression analyses, it was concluded that for the ISST, anaerobic energetic pathways contribute mainly to energy supply for peak sprint time, while aerobic energetic pathways also contribute to energy supply for total sprint time. Energy during the ISRT is supplied mainly by the aerobic energy system. Depending on the aspect of physical performance a coach wants to determine, the ISST or ISRT can be used. KEY WORDS. Interval Shuttle Sprint Test, Interval Shuttle Run Test, maximal oxygen uptake, Wingate test, intermittent sport physiology INTRODUCTION I ntermittent sports, such as field hockey, re- quire a high degree of physical fitness (23). Time-motion analysis indicates that in women’s field hockey, about 20% of the game is spent in high-intensity activity, such as running and sprinting (18). These high-intensity activities of short du- ration (5 seconds, on average) are alternated with low- intensity activities such as walking and jogging (18 sec- onds, on average). The skill requirements and postural stress (semicrouched posture) are superimposed on the work rate demanded by the game and its pattern of play (23). It is therefore appropriate to view a field hockey game as aerobically demanding, with frequent, though brief, anaerobic efforts superimposed (21). High-intensity efforts rely predominantly on the immediate (adenosine triphosphate phosphocreatine) and short-term (anaerobic glycolysis) anaerobic energy systems. The aerobic energy system is important during prolonged intermittent exer- cise. Evidently, the energetics of field hockey require an interaction of all 3 energy systems, with each system playing a significant yet specific role in energy supply during the game (7, 21, 31). A number of intermittent field tests have been devel- oped to evaluate physical performance of players in in- vasion games such as field hockey and soccer (1–3, 5, 8, 12, 19, 28). In this line, we developed 2 field tests: the Interval Shuttle Sprint Test (ISST) and the Interval Shuttle Run Test (ISRT) (14–17). The ISST comprises 10 shuttle sprints, each shuttle sprint consisting of 2  6m and 2  10 m of sprinting back and forth, starting every 20 seconds. The peak sprint time, the total sprint time, and the drop-off index express the performance. The ISRT consists of 30-second shuttle runs over 20 m, inter- spersed with 15-second walking periods at progressively increasing speeds until exhaustion. Intermittent field tests should challenge the energy systems in a manner that closely replicates the game situation. Therefore, it is important to investigate the relationship between anaer- obic and aerobic energy systems and intermittent field test performances. The relationship between intermittent sprint field tests (i.e., tests of repeated sprint ability) and measures of anaerobic and aerobic energy systems has been well documented, but study results show contradictory out- comes (1, 2, 5, 8, 28). Several reasons may be offered to explain these varying results. First, there is a diversity in repeated sprint test protocols (i.e., differences in sprint distances [20–40 m], number of repetitions [6–18], and recovery periods [15–25 seconds]). Second, there are a va- riety of laboratory tests to measure anaerobic power and capacity, such as all-out cycle ergometer sprints of 10, 30, and 90 seconds; all-out treadmill sprints; an intermittent cycle ergometer and treadmill test; and laboratory tests to measure aerobic capacity, such as maximal cycle er- gometer and treadmill tests. Third, differences in homo- geneity and performance levels of players may account for different study outcomes. Intermittent endurance field tests, such as the Intermittent Endurance Test (3) and, more recently, the Yo-Yo Intermittent Recovery Test (12), have been related to aerobic energy system measures. Re- sults indicate moderate correlations between intermittent endurance field tests and V ˙ O 2 max. Up until now, most research on the relationship be- tween intermittent field tests and energy-producing sys- tems has been limited to a comparison with only one of the energy systems as a criterion measure (1–4, 12). How- ever, research should focus on the contribution of all en- ergy systems at the same time, because the energetics of intermittent field tests are complex, with anaerobic and aerobic energy systems interacting and playing a specific role in energy supply during test performance. Therefore, the purpose of the present study was to evaluate the role of anaerobic and aerobic energy systems with regard to energy supply for 2 intermittent field tests (i.e., the ISST and the ISRT) by relating these field tests with laboratory tests for measuring anaerobic and aerobic performance. We hypothesized that anaerobic as well as aerobic per- formance would be related to the ISST and the ISRT. However, we expected the anaerobic and aerobic perfor-