Contraction force specificity and its relationship to functional performance NIGEL HARRIS 1 , JOHN CRONIN 2 , & JUSTIN KEOGH 1 1 Institute of Sport & Recreation Research New Zealand, Auckland University of Technology, Auckland, New Zealand and 2 School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Perth, WA, Australia (Accepted 9 February 2006) Abstract Best practice for improving strength and power through resistance strength training has been the subject of much research and subsequent conjecture. Much of the conjecture can be attributed to methodological discrepancies. The type of dynamometry used in testing, the training experience of research participants, the specific technique employed in a lift, and the methods of collection and calculation all impact on the final variables of interest. This review examines contraction force specificity by first addressing the methodological issues surrounding our interpretation of the results. Then we address the kinematics and kinetics associated with single and multiple repetitions in relation to the development of strength, power, and functional performance. This discussion provides the delimitations for analysis of subsequent training studies. Finally, recommendations are formulated with the aim of assisting assessment and training practice as well as providing directions for future research. The results of this review suggest that the enhancements in performance resulting from resistance training are context specific in experienced resistance-trained participants. Thus, specific conditioning could be required to achieve improvements in functional performance in this group. Keywords: Resistance training, kinetics, kinematics, assessment Introduction Strength and power are critical to the performance of many athletic tasks and everyday activities (Stone, Moir, Glaister, & Sanders, 2002). Consequently, best practice for improving strength and power through resistance strength training has been the subject of much research and subsequent conjecture. Some of the conjecture can be attributed to the multi-factorial nature of strength and power. For example, strength has been generally defined as the peak force devel- oped in a maximal voluntary isometric contraction, or as the maximum load that can be lifted for one repetition (1-RM). Power is defined as the rate at which mechanical work is performed or as the product of force and velocity (Abernethy, Wilson, & Logan, 1995; Harman, 1993; Sale, 1991). However, other definitions acknowledge the specificity of strength and power, their expression being affected by body position, movement pattern, velocity, con- traction type, and contraction force (Sale, 1991). That is, strength and/or power exhibited under one set of conditions could be quite different under another set of conditions (Atha, 1981). The purpose of this review is to assess the effects of contraction force specificity on changes in strength, power, and functional performance. Sale and MacDougall (1981) proposed that the optimal load (contraction force) for strength improve- ment depends on a needs analysis of the functional task of interest. It was suggested that if the activity involved a few brief contractions, 90 – 100% 1-RM training would be most specific, whereas if the activity involved a ‘‘large’’ number of contractions, 75 – 80% 1-RM training would be more appropriate. Sale and MacDougall (1981) suggested that the motor unit activation patterns and biochemical adaptations resulting from each loading scheme constituted a sound rationale for the use of these specific loading patterns. However, given the ad- vances in strength and conditioning practice, the myriad of loading schemes or protocols available to the strength and conditioning practitioner and the individual responses known to occur to these different loading schemes, this proposition could be overly simplistic. Correspondence: N. Harris, Institute of Sport & Recreation Research New Zealand, Auckland University of Technology, Private Bag 92006, Auckland 1020, New Zealand. E-mail: nigel.harris@aut.ac.nz Journal of Sports Sciences, January 15th 2007; 25(2): 201 – 212 ISSN 0264-0414 print/ISSN 1466-447X online Ó 2007 Taylor & Francis DOI: 10.1080/02640410600630910