european college of sport science

OP-TT02 Training & Testing 2
BRIEF FORCE PULSES: THE RELATIONSHIP BETWEEN THE PEAK FORCE AND RATE OF FORCE DEVELOPMENT
JARIC, S., SUZOVIC, D., NEDELJKOVIC, A.
UNIVERSITY OF BELGRADE (BELGRADE, SERBIA), UNIVERSITY OF DELAWARE (NEWARK, USA)
Introduction: While the standard strength tests assess the ability to exert high force of sustained maximum isometric and isotonic contractions,
a number of important functional movements are based on brief ‘force pulses’ exerted in either discrete (e.g., postural corrections,
pointing) or repetitive movements (walking, running, cycling). Therefore, in addition of requiring high forces that may be either painful or
inappropriate for some populations, the standard strength tests may not capture the activation pattern of brief muscular actions. The aim
of this study was to evaluate the relationships between the peak force and the rate of force development and relaxation of the brief force
pulses (BFP) as candidate for a novel test of neuromuscular function.
Methods
Within the first experiment, 12 participants performed consecutive series of 12 isometric BFP (i.e., a rapid exertion of force to a prescribed
level followed by rapid relaxation) targeting 30%, 50% and 70% of MVC both within-day and across days. Individual BFP provided the
peak force (PF) and the rates of force development (RFD) and relaxation (RFR). The data from each series were, thereafter, presented on
RFD-PF and RFR-PF graphs and the linear regression was assessed. These data were used for the assessment of the within-day and
between-day reliability through the intra-class correlation coefficients (ICC) and coefficients of variation (CV%). Within the second experiment,
additional 36 participants performed the same test of the knee flexors and extensors, and elbow flexors and extensors. These data
served for the general assessment of the RFD-PF and RFR-PF relationship, as well as for a comparison of the variables obtained from
different muscle groups.
Results: The first experiment revealed moderate to high within-day reliability (i.e., ICC, range 0.71-0.98; CV%, range 1.8-141.5) as well as
moderate to high between-day reliability (i.e., ICC, range 0.58-0.92; CV%, range 4.1-205.8) of the slopes and intercepts of the PF-RFD and
PF-RFR relationship. The second experiment revealed similar slopes across the tested groups, while the intercepts were either a relatively
low or close to zero. PF-RFD and PF-RFR slopes also moderately correlated. When the data of different muscle groups were related, the
slopes moderately correlated, but not the intercepts. Of utmost importance, however, could be exceptionally high correlations.
Discussion: In general, the obtained results suggest both invariant and subject specific force-time profiles of BFP across a range of exerted
forces. Of particular importance for future BFP consideration could be an apparent functional importance of the obtained slopes
(e.g., discerning ‘strong individuals’ from ‘quick ones’), simplicity (single variable could be the outcome), generalizability across muscle
groups, and low level of exerted forces. Therefore, although the external validity remains to be examined, BFP could be a test complementary
to the standard strength tests.
INTERSESSION RELIABILITY OF VERTICAL JUMP HEIGHT
SØRENSEN, H., IVERSEN, K.
UNIVERSITY OF AARHUS
Introduction: The usefulness of measurements in research depends on the extent to which the researcher can rely on data as accurate
and meaningful indicators of a behavior. In short, the measurements have to be reliable and valid (Portney and Watkins, 2008).
The vertical countermovement jump (CMJ) is often used as a physical performance test. Researchers routinely seek to enhance the reliability
of the CMJ height measurement by having subjects perform a number of jumps, typically 3 or 5, and then using either the best or
the average for further analyses. However, studies show that there does not exist a consistent protocol for either the number of jumps or
whether to use best of or average (e.g. Bazett-Jones et al., 2008, Vanezis and Lees, 2005, Hamilton, 2008). The purpose of this study is to
investigate how the number of jumps and the use of best of or average affect the reliability of the CMJ measurements.
Methods: Twenty-two males (25.2 +/- 1.95 years; 1.81 +/- 0.06 meters; 75.9 +/- 6.38 kg [mean +/- SD]) went through the same programme
twice (test and retest) with one week in between. The programme started with five minutes warm-up on a cycle ergometer
followed immediately by 10 maximal CMJs on a force plate with one minute rest before each jump. From the data, 4 series of 10 testretest
intraclass correlation coefficients (ICC) were calculated. In two series, A and B, jump height was calculated from the vertical impulse,
while jump height in the other two series (C+D) was calculated from flight time. The first ICC in each series (A-D) was calculated
from the first jump in test and retest. The second ICC in series A+C was calculated from the average of the two first jumps in test and
retest, and in series B+D from the best of the two first jumps in test and retest. The same procedure was used for the third ICC and so on
until the tenth ICC where all the 10 jumps from test and retest were used in the ICC calculations.
Results: The series A, which was calculated from the vertical impulse and using the average, gave the following ICCs: 1 jump = 0.74; 2
jumps = 0.82; 3 jumps = 0.86; 10 jumps = 0.91. The series B, C and D had lower ICCs and in that order.
Discussion: The results showed three things: (1) It is more reliable to use vertical impulse than flight time, (2) it is more reliable to use
average than best of, and (3) ICC increased steeply through the first three jumps and then just slightly. Therefore, when using the CMJ as
a physical performance test, one should use vertical impulse and average of at least 3 jumps.
References
Portney, L, Watkins, M. (2008). Foundation of Clinical Research. Application to Clinical Practice, p. 77, Pearson Prentice Hall, New Jersey.
Bazett-Jones DM, Gibson MH, McBride JM. (2008). J Strength Cond Res, 22(1), p. 25-31.
Vanezis A, Lees AD. (2005). Ergonomics, 48, p. 1594-1603.
Hamilton RT, Shultz SJ, Schmitz RJ, Perrin DH. (2008). J Athl Train, 43(2), p. 144-151.
A COMPARISON OF SUCCESSFUL AND UNSUCCESSFUL ATTEMPTS IN 1 RM BENCH PRESS.
VAN DEN TILLAAR, R., ETTEMA, G.
1. SOGN AND FJORDANE UNIVERSITY COLLEGE, 2. RESEARCH CENTRE FOR SPORT, HEALTH AND HUMAN DEVELOPMENT, PORTUGAL, 3.
NTNU
Introduction: One of the most popular exercises in strength training for the upper body is bench press. The movement consists of different
periods. The sticking period is probably the weakest link in the upward movement and is probably the period at which an attempt will be
successful or not. In maximal lifting, understanding of the causes of this sticking period and its effects could help to enhance the training
methods. Therefore the purpose of this study was to compare the differences in EMG and kinematics between successful and unsuccessful
attempts in bench press at 1RM in recreational weight-training athletes with special attention to the sticking period.
296 14 TH
ANNUAL CONGRESS OF THE EUROPEAN COLLEGE OF SPORT SCIENCE