european college of sport science

14:15 - 15:15
Poster presentations
PP-TT09 Training and Testing 9
DOES PLYOMETRIC TRAINING IMPROVE STRENGTH PERFORMANCE? A META-ANALYSIS
SAEZ-SAEZ DE VILLARREAL, E., REQUENA, B.
UNIVERSITY PABLO DE OLAVIDE (SEVILLA)
PP-TT09 Training and Testing 9
Plyometric training (PT) improves strength performance. However, the effectiveness of PT depends upon various factors. A meta-analysis
of 15 studies with a total of 24 effect sizes (ES) was carried out to analyze the role of various factors on the effects of PT on strength performance.
The inclusion criteria for the analysis were: a) studies using PT programs for lower limb muscles b) studies employing true
experimental design and valid and reliable measurements; c) studies including enough data to calculate ES. When subjects can adequately
follow plyometric exercises, the training gains are independent of fitness level. Subjects in either good or bad physical condition,
benefit equally from plyometric work, although men obtain similar strength results with women following PT. With relation to the variables
of performance, training volume for less than 10 weeks and with more than 15 sessions, as well as the implementation of high intensities
programs- with more than 40 jumps per session-, were the strategies that seem to maximize the probability to obtain significant greater
improvements in performance (p< 0.05). In order to optimize strength enhancement, the combination of different types of plyometrics
with weight-training would be recommended, rather than utilizing only one form (p< 0.05). However, no extra benefits were found to be
gained from doing plyometrics with added weight. The responses identified in this analysis are essential and should be considered by
the strength and conditioning professional with regard to the most appropriate dose-response trends PT to optimized strength gains.
NEUROMUSCULAR AND METABOLIC FATIGUE WITH THE SAME ABSOLUTE AND RELATIVE INTENSITY AFTER STRENGTH
TRAINING
IZQUIERDO, M., IBAÑEZ, J., CALBET, J.A.L., GONZÁLEZ-IZAL, M., NAVARRO-AMEZQUETA, I., MALANDA, A., GONZÁLEZ-
BADILLO, J.J., HÄKKINEN, K., KRAEMER, W.J., GOROSTIAGA, E.M.
GOVERNMENT OF NAVARRA
Introduction: Muscle hypertrophy (1,3), increases in maximal strength and power output (2-3) and enhanced agonist EMG activity (1,3) are
typical adaptations during short-term heavy resistance training (i.e. 7-10 weeks). However, the effects of resistance training on dynamic
exercise-induced fatigue with the same absolute and relative loading as in pretraining remain to be elucidated. This study examined the
effects of heavy resistance training on dynamic exercise-induced fatigue task (5X10RM leg-press) after two loading protocols with the
same relative intensity (%)(5x10RMRel) and the same absolute load (kg)(5x10RMAbs) as in pretraining in men(n=12).
Methods: Maximal strength and muscle power, surface EMG changes [amplitude and spectral indices of muscle fatigue], and metabolic
responses (i.e.blood lactate and ammonia concentrations) were measured before and after exercise.
Results and Discusion
The main findings of this study were that after short-term heavy resistance training, when the relative intensity of the fatiguing dynamic
protocol was kept the same 1) the magnitude of exercise-induced loss in maximal strength was greater than that observed before training,
2) the peak power lost after 5x10RMRel (58-62%, before and after training) was greater than the corresponding exercise-induced
decline observed in maximal dynamic (23-34%) and isometric strength (12-17%), but this was followed by a more rapid and complete
recovery, 3) the magnitude of the exercise-induced neuromuscular changes were similar than before training, as well 4) higher accumulation
of blood lactate and ammonia concentration after training were observed. After a short-term strength training period, the main
mechanisms responsible for the increased capacity to work with the same relative intensity are mainly of a peripheral nature, since
similar neural adjustments but higher accumulated fatigue and metabolic demand (i.e. blood lactate and ammonia accumulation) were
observed after multiple sets of dynamic fatiguing high-power contractions with the same relative load as in pretraining. This result may
indicate that rate of fatigue development (i.e. power and MVC) was faster and more profound after training despite using the same
relative intensity. The fact that the same relative loading leads to increased rate of fatigue development after training has important
practical implications. This may suggest that despite the enhanced ability to produce maximal strength and muscle power after a
strength training program, it is important to note that when prescribing training programs a similar relative load as in pretraining could
lead to a greater rate of fatigue development and, therefore, may induce different training effects.
References
1.Aagaard P, Simonsen EB, Andersen JL, et al. J Appl Physiol 2002; 93(4):1318-26.
2.Häkkinen K, Alén M and Komi PV. Acta Physiol Scand 1985; 125(4):573-585.
3.Izquierdo M, Ibañez J, González-Badillo JJ, et al. J Appl Physiol 2006; 100(5):1647-56.
Supported by the Ministry of Education of Spain (Sport and Physical Activity DEP2006-56076)
MAXIMAL DYNAMIC FORCE DEVELOPMENT IN THE SHOULDERS UNDER STABLE AND UNSTABLE CONDITIONS
RUSTAD, O., SEILER, S.
UNIVERSITY OF AGDER
Purpose: The use of surface instability has gained popularity in strength training. However, the impact of unstable conditions during
training on functional changes in force production is not well established and methods of isolating instability to specific joint complexes
are lacking. In this study we have quantified the impact of surface instability on maximal force development of the shoulder complex
during a weight bearing (closed kinetic chain) push-up task. In addition, the test-retest reliability of maximal dynamic force measurements
was quantified under both conditions.
Methods: 20 physically active university students (14 males, 6 females) performed 2 maximal dynamic force tests under stable and unstable
conditions. Maximally explosive push-ups were performed on a force platform while holding push-up bars (Stable condition). This
436 14 TH
ANNUAL CONGRESS OF THE EUROPEAN COLLEGE OF SPORT SCIENCE