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Purpose: This investigation examined the reliability and usefulness of the isometric mid-thigh pull (IMTP) and isometric squat (ISqT) performed at the same knee and hip angles. The scores produced in each test were compared to determine the magnitude of differences between tests. Methods: Twenty six male and female athletes (23.6±4.3 y; 1.75±0.07 m; 68.8±9.7 kg) performed 2 maximal repetitions of the IMTP and ISqT following a specific warm up. Results: Maximum force, absolute peak force (PF), relative PF, allometrically scaled PF, rate of force development (RFD) (0 - 200 and 0 - 250 ms) and impulse (0 - 300 ms) were deemed reliable (ICC ≥ 0.86 and CV ≤ 9.4%) in the IMTP and ISqT based on predetermined criteria (ICC ≥ 0.8 and CV ≤ 10%). Impulse (0 - 200 ms and 0 - 250 ms) were reliable in the ISqT (ICC ≥ 0.92 and CV ≤ 9.9%). Participants produced significantly (p < 0.05) greater PF and impulse (0 - 300 ms) during the ISqT compared with the IMTP. When split by sex, female participants produced significantly greater PF (p = 0.042) during the ISqT with no significant differences among male participants (p = 0.245). Both tests are capable of detecting changes in performance in maximum force and absolute PF. Conclusions: Both tests are reliable for non-time dependent maximal strength measures when measured at the same knee and hip angles. The ISqT may be preferred when coaches want to test an athlete's true maximum lower limb strength, especially female athletes.
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A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Note. This article will be published in a forthcoming issue of the
International Journal of Sports Physiology and Performance. The
article appears here in its accepted, peer-reviewed form, as it was
provided by the submitting author. It has not been copyedited,
proofread, or formatted by the publisher.
Section: Original Investigation
Article Title: A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday
Reliability, Usefulness and the Magnitude of Difference Between Tests
Authors: Claire J Brady1, Andrew J Harrison1, Eamonn P Flanagan2, G Gregory Haff3 and
Thomas M Comyns1
Affiliations: 1Department of Physical Education and Sport Sciences, University of Limerick,
Limerick, Ireland. 2Sport Ireland Institute, IIS Building, National Sports Campus,
Abbotstown, Dublin 15, Ireland. 3Centre for Exercise and Sport Science Research, Edith
Cowen University, Joondalup, Western Australia, Australia.
Journal: International Journal of Sports Physiology and Performance
Acceptance Date: November 9, 2017
©2017 Human Kinetics, Inc.
DOI: https://doi.org/10.1123/ijspp.2017-0480
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
A comparison of the isometric mid-thigh pull and isometric squat: intraday reliability,
usefulness and the magnitude of difference between tests
Submission type: Original Investigation
Claire J Brady1, Andrew J Harrison1, Eamonn P Flanagan2, G Gregory Haff3 and Thomas M
Comyns1
1 Department of Physical Education and Sport Sciences, University of Limerick, Limerick,
Ireland.
2 Sport Ireland Institute, IIS Building, National Sports Campus, Abbotstown, Dublin 15,
Ireland.
3 Centre for Exercise and Sport Science Research, Edith Cowen University, Joondalup,
Western Australia, Australia.
Corresponding Author:
Claire Brady,
Department of Physical Education and Sports Sciences,
University of Limerick,
Limerick,
Ireland
Email: claire.brady@ul.ie
Telephone: +353 85 7321128
Preferred running head: Reliability of isometric strength testing
Abstract word count: 250
Text-only word count: 3678
Number of References: 31
Number of Figures: 5
Number of Tables: 5
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Abstract
Purpose: This investigation examined the reliability and usefulness of the isometric mid-thigh
pull (IMTP) and isometric squat (ISqT) performed at the same knee and hip angles. The scores
produced in each test were compared to determine the magnitude of differences between tests.
Methods: Twenty six male and female athletes (23.6±4.3 y; 1.75±0.07 m; 68.8±9.7 kg)
performed 2 maximal repetitions of the IMTP and ISqT following a specific warm up. Results:
Maximum force, absolute peak force (PF), relative PF, allometrically scaled PF, rate of force
development (RFD) (0 200 and 0 250 ms) and impulse (0 300 ms) were deemed reliable
(ICC ≥ 0.86 and CV ≤ 9.4%) in the IMTP and ISqT based on predetermined criteria (ICC ≥ 0.8
and CV ≤ 10%). Impulse (0 200 ms and 0 250 ms) were reliable in the ISqT (ICC ≥ 0.92
and CV 9.9%). Participants produced significantly (p < 0.05) greater PF and impulse (0
300 ms) during the ISqT compared with the IMTP. When split by sex, female participants
produced significantly greater PF (p = 0.042) during the ISqT with no significant differences
among male participants (p = 0.245). Both tests are capable of detecting changes in
performance in maximum force and absolute PF. Conclusions: Both tests are reliable for non-
time dependent maximal strength measures when measured at the same knee and hip angles.
The ISqT may be preferred when coaches want to test an athlete’s true maximum lower limb
strength, especially female athletes.
Keywords: isometric strength, force-time curve, maximum strength, explosive strength,
performance testing
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Introduction
Isometric tests such as the isometric mid-thigh pull (IMTP) and isometric squat (ISqT)
allow the assessment of athletes’ strength qualities from a force-time curve and are used to
assess skeletal muscle function.1,2 Buckner, et al. 3 suggested that typical strength assessments
such as 1RM testing are skills and that using multiple measures such as the IMTP or ISqT may
be more advantageous for defining true measures and changes in strength. The IMTP is
designed to replicate the body position at the beginning of the second pull position of the clean
or the snatch.1 The second pull position (130 140° knee angle with an upright trunk position1)
is the strongest and most powerful position during weightlifting movements, generating the
highest forces and velocities of any part of the lifts.5 From the force time curve produced in
these tests, there are a number of variables that can be examined. Peak force (maximum force
produced) is indicative of “maximum strength” and rate of force development (RFD) is
indicative of an athletes ability to produce maximal force in minimal time.6 To describe
different portions of the force-time curve, Zatsiorsky 7 calculated the index of explosiveness
(IES), reactivity coefficient (RC), S-gradient and A-gradient. The IES refers to the ability to
exert maximal forces in minimal time and the RC expresses the IES relative to body weight.8
The S-gradient quantifies RFD at the beginning of muscular effort whereas the A-gradient
characterises the late stages.7 While Haff, et al. 9 has applied these to the force-time curve of
an IMTP, they have not yet been applied to the ISqT. Impulse determines the change in
momentum of an athlete and is an important performance related characteristic.
With the increased popularity of isometric tests being used to assess strength qualities,
it is important that the data obtained to prescribe, monitor and alter an athletes’ training
programme is reliable. Superior reliability, results in better precision of single measurements
and enhanced tracking of changes in measurement in both research and practical settings.10 To
assess test-retest reliability, it is recommended that the intraclass correlation coefficient (ICC)
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
and the typical error expressed as a coefficient of variation (CV) should be calculated10 along
with 95% confidence intervals (CIs).7 While there are no predetermined standards set for
measurements of reliability in sports science, the literature has commonly used a threshold of
an ICC ≥ 0.80 and a CV ≤ 10%.10
Early research on the IMTP only reported the ICC as the reliability measure and
reported peak force (PF) and peak RFD (pRFD) as reliable.1,11-13 PF is by far the most reliable
variable, with an ICC 0.92 and a CV 5% reported in the literature.9,14-16 Research on the
reliability of the ISqT is limited compared to the IMTP, but generally results in PF being the
most reliable variable, with tests performed at various knee angles (ICC ≥ 0.97). 11,17-19
Variables including RFD and impulse have been reported as reliable in the IMTP 9,14-16 and
ISqT.18 There are different methods for calculating the RFD including pre-set time bands, 2,9,20
determining the pRFD across various windows 1,2,9,20,21 and using the slope of the curve from
the initial rise to the maximum force expression (average RFD).9,22 Haff, et al. 9 found that
using selected time bands for the quantification of the RFD offers greater reliability compared
with the quantification of the pRFDs. Average RFD (avgRFD) 9, has been deemed unreliable
and pRFD during a 20 ms sampling window (pRFD20) has only met the ICC criteria for
acceptable reliability (ICC ≥ 0.93 and CV ≥ 12.9%).9,15,16 Maffiuletti, et al. 23 noted that smaller
epochs are more sensitive to changes in the slope of the curve and therefore less reliable.
Nuzzo, et al. 11 reported that male NCAA division 1 American Football players and
track and field athletes produced 12.5% more relative PF during the ISqT when compared with
the IMTP, performed at the same knee angle (140°). Both tests were reported as reliable (r
0.98). There is limited research conducted among female athletes performing an ISqT. Sex
differences in strength exist in the upper body with females demonstrating weakness compared
to their male counterparts.24 The main difference between an IMTP and ISqT is the elimination
of the upper limb during an ISqT and being cued to “push” rather than “pull”. In addition,
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
limited reliability research has been conducted in the ISqT on variables other than PF, such as
RFD (sampling windows), pRFD and impulse.
Once a performance test is determined reliable, the smallest worthwhile change (SWC)
should be calculated and Hopkins 10 suggests using the typical error (TE) alongside the SWC
to allow practitioners to make a well-informed decision on whether a change is both of practical
significance (> SWC) and real (greater than the noise of the test, > TE). This research provides
new information on the usefulness of each test looking at the TE compared to the SWC.
No previous research has compared the reliability and results obtained during the IMTP
and ISqT performed at the same knee and hip angles. Therefore, the aim of the current study
was to determine the intraday reliability of the IMTP and ISqT performed at the same knee and
hip angle, define the usefulness of the tests and determine the magnitude of effect between the
IMTP and ISqT among male and female athletes.
Methods
Participants
Sixteen male (23.0 ±4.8 y; 1.79 ±0.05m; 72.8 ±10.4 kg) and ten female athletes (24.5
±3.1 y; 1.68 ±0.03 m; 62.5 ±3.4 kg) from track & field, boxing, modern pentathlon, canoeing,
rowing, badminton and Taekwondo took part in this study. All participants had at least 6
months of resistance training experience. All participants provided written informed consent
prior to participation in accordance with the ethical requirements of the Research Ethics
Committee.
Study Design
A cross sectional study design with repeated measures was used. This study assessed
the intraday reliability of the IMTP and ISqT performed at the same knee and hip angle to
determine the reliability of maximum force, PF, RFD (sampling windows), pRFD, avgRFD,
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
impulse, IES, RC, S-gradient and A-gradient. The mean scores achieved in each test were
compared. All participants took part in a familiarisation session one week prior to the testing
session. The IMTP/ISqTs were randomised among participants.
Methodology
Participants took part in a familiarisation session that firstly included an explanation of
the study and signing of the informed consent. Participants then performed a general warm up
consisting of 3 minutes of cycling, 10 bodyweight squats, 10 bodyweight walking lunges and
10 glute bridges. Participants were then set in the correct position for the IMTP, which
consisted of a mean knee angle of 136 ± and a hip angle of 137 ± 2°. Participants were
required to maintain the position throughout the test. Knee angles and hip angles were
measured using a hand-held goniometer, grip- and foot- width were measured and remained
consistent between trials. Then each participant performed an IMTP specific warm up
previously reported in the literature 25, which consisted of pulling the IMTP bar for 5 seconds
at a self-directed 50%, 3 seconds at 70 80%, 3 seconds at 90% of maximal effort with 1
minute recovery between warm up efforts. Participants completed 3 maximal efforts lasting 5
seconds. During the IMTP, participants used lifting straps to standardise grip strength.25 For
each trial participants were instructed to pull as hard and as fast as you can, push the ground
away, drive your feet into the ground and the bar from the floor” to ensure maximal force was
achieved.26 Participants were then set in the position for the ISqT, which adopted the same knee
and hip angles attained during the IMTP, with the bar positioned across the shoulders. The
same specific warm up and instruction was given with the exception of “push” instead of “pull”.
One week later, participants completed the testing session. The order sequences of tests
were randomised among participants. Participants completed the general warm up followed by
the specific warm up of the first test to be completed. Participants were then given 2 minutes
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
rest before completing 2 maximal effort trials with 2 minutes between trials. Participants were
instructed to get ready, to pre-tense, and then were given a countdown of 3, 2, 1, PULL!”
Verbal encouragement was provided during each trial. They then rested for 5 minutes before
completing the warm up for the second test (IMTP/ISqT) followed by 2 maximum efforts with
2 minutes rest between trials. Participants completed a third trial if they lost their position or
grip.
All isometric testing was conducted on a custom-made Sorinex isometric rack
(Lexington, South Carolina, USA), allowing the placement of the bar at 0.5 cm intervals
permitting the desired position in each participant. The rack was anchored to the floor and
placed over a Kistler (Winterthur, Switzerland) force platform sampling at 1000 Hz.
Isometric force-time curve analysis
All force-time curves were analysed with the use of a custom built spreadsheet to
determine specific force-time characteristics. The collection period for each trial was set at 12
seconds and a baseline was measured during the 3 second countdown prior to the initiation of
the pull. The criterion onset threshold and onset of the contraction was defined as the point
where the force exceeded 5 SD from baseline.27 The maximum force generated during the 5
seconds was reported as the maximum force. Absolute PF was reported as the maximum force
minus the participant’s body weight. Absolute PF was also reported relative to body mass
(N/kg) and body weight (N/N). Additionally, absolute PF was scaled allometrically (N/kg0.67)
to measure muscle strength independent of body size.12
RFD was analysed with methods previously reported in the literature.9 Precisely, RFD
was calculated (∆Force/∆Time) and was applied to specific time bands (0 30, 0 50, 0 90,
0 100, 0 150, 0 200, 0 250 ms). pRFD was then determined as the highest RFD during
a 2- (pRFD 2), 5- (pRFD 5), 10- (pRFD 10), 20- (pRFD 20), 30- (pRFD 30) and 50-millisecond
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
(pRFD 50) sampling windows. AvgRFD was calculated from the PF achieved and the time
elapsed between the initiation of the pull and the PF values. Impulse was measured by average
force divided by the change in time over 100 ms, 200 ms, 250 ms and 300 ms.
The IES is calculated identical to the avgRFD. The RC was calculated using the PF and
time to PF and the participants body weight [PF/ (TPF x BW)]. The S-gradient was calculated
using half the PF (PF0.5) and the time to achieve it (TPF0.5): (PF0.5/TPF0.5). Finally the A-
gradient was calculated by using the PF0.5, TPF and TPF0.5: [PF0.5/ (TPF-TPF0.5)].7
Statistical Analyses
All force-time data were analysed with the use of a custom spreadsheet. Normality of
data was assessed by Shapiro-Wilk statistic. Reliability was calculated by determining the
coefficient of variation (calculated as the typical error and expressed a CV) and the intraclass
correlation coefficient (ICC) and 95% confidence interval (95% CI) using a Microsoft Excel
spreadsheet.28 Acceptable reliability was determined at an ICC ≥ 0.8 and a CV ≤ 10%.10 Paired
t-tests with an alpha level of p 0.05 were used to determine if differences existed between
mean absolute PF, relative PF (N/kg), allometrically scaled PF, RFD (0 200 ms), RFD (0
250 ms) and impulse (0 300 ms) values produced in the IMTP and ISqT. Participants were
then split by sex for this analysis to determine if sex differences existed. Paired t-test values
were reported with a Holm’s sequential Bonferroni method 29 in order to control for type I
errors. To determine the magnitude of effect within group differences in test scores, a Hedges’
g effect size test was performed between the mean values produced in the IMTP and ISqT. The
magnitude of Hedges’ g was interpreted using Cohen’s scale as trivial (g < 0.2), small (0.2 ≤ g
< 0.5), moderate (0.5 ≤ g <0.8) and large (g ≥ 0.8).30 Typical error (TE) was calculated and the
usefulness of the test was determined by comparing the TE to the smallest worthwhile change
(SWC) calculated on a Microsoft Excel spreadsheet.28 The SWC was determine by multiplying
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
the between-subject SD by 0.2 (SWC0.2) 31, which is the typical small effect or 0.5 (SWC0.5) 30,
which is an alternate moderate effect. If the TE was below the SWC, the test was rated as
“good”, if the TE was similar to SWC it was rated as “ok” and if the TE was higher than the
SWC the test was rated as “marginal”.31
Results
Descriptive statistics for male and female participants for the variables that attained a
criterion of an ICC ≥ 0.8 and a CV ≤ 10% are shown in Table 1 for the IMTP and Table 2 for
the ISqT along with the TE, SWC0.2 and SWC0.5. Figure 1 shows the variables that achieved a
criterion of an ICC ≥ 0.8 and a CV ≤ 10% in either test. While impulse 0 – 200 ms and 0 250
ms were determined reliable in the ISqT, they were deemed unreliable in the IMTP (CV >
10%). RFD (0 30 ms, 0 50 ms, 0 90 ms, 0 100 ms and 0 150 ms), pRFD (2 ms, 5ms,
10 ms, 20 ms, 30 ms and 50 ms), avgRFD, impulse (0 100 ms), IES, RC, S-gradient and A-
gradient were deemed unreliable in both the IMTP and ISqT (ICC < 0.8 and/or CV > 10%)
(Figure 2).
Differences between mean absolute PF, relative PF (N/kg), allometrically scaled PF,
RFD (0 200 ms), RFD (0 250 ms) and impulse (0 300 ms) produced during the IMTP and
ISqT are shown in Table 3. Holm’s Sequential Bonferroni adjusted p-values show significant
differences (p < 0.05) exist between absolute PF (p = 0.006), relative PF (p = 0.006),
allometrically scaled PF (p = 0.006) and impulse (0 300 ms) (p = 0.036) values between the
IMTP and ISqT with the ISqT producing significantly higher results than the IMTP (Figure 3).
Figure 4 details the magnitude of effect between the IMTP and ISqT. Participants were split
by sex to determine if sex differences existed between tests. Among males, no significant
differences were detected between any variable (Table 4). Among females, significant
differences were observed between absolute PF (p = 0.042), relative PF (N/kg) (p = 0.042) and
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
allometrically scaled PF (p = 0.042) with the ISqT producing significantly (p < 0.05) higher
results (Table 5). Figure 5 details differences individual and group mean values of the IMTP
and ISqT for male and female participants for measures of absolute peak force, allometrically
scaled PF, RFD 0 250 ms and impulse 0 300 ms.
Discussion
The aim of this study was to determine the reliability of the IMTP and ISqT performed
at the same knee and hip angles, define the usefulness of the tests and determine the magnitude
of effect between the IMTP and ISqT among male and female athletes and report reference TE
and SWC values. This study provides new information on the reliability and usefulness of both
tests and the mean values produced at the same knee and hip angle. Variables that were reliable
in both tests include, maximum force, absolute PF, relative PF (N/N) and (N/kg), allometrically
scaled PF, RFD (0 200 ms and 0 250 ms) and impulse (0 300 ms) (ICC ≥ 0.8 and CV
10%). Impulse (0 200 ms) and (0 250 ms) were deemed reliable in the ISqT. All short
sampling windows of RFD (up to 150 ms), pRFD (up to 50 ms), impulse (0 100 ms), IES,
RC, S-gradient and A-gradient were deemed unreliable for both tests.
PF has been reported as the most reliable variable measured during an IMTP. Previous
research reported ICCs ≥ 0.92 and CV ≤ 5%9,14-16, which is similar to the results of this study.
However, differences exist in the definition of PF with some research including body weight
in the calculation and other research calculating PF as maximum force minus body weight
Beckham, et al. 2 included body weight in their calculation whereas West, et al. 13 calculated
PF minus the participant’s body weight. Some research does not clearly state whether body
weight was included 12 leaving the interpretation of results confounding for coaches. Previous
research has reported that RFD measures (0 200 ms and pRFD) are reliable with ICC > 0.8
even though the CV > 15%.14,16 Haff, et al. 9 reported RFD sampling windows from 0 30 ms
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
up to 0 250 ms as reliable (ICC > 0.8 and CV < 10%), different to the results found in this
study. Maffiuletti, et al. 23 noted when measuring RFD, familiarisation is very important and
prolonged practice procedures may be required to obtain reliable data. The participants used in
the study by Haff, et al. 9 had a lot of experience in producing force in the second pull position
compared to the participants used in this study and this may explain the difference in results.
To achieve reliable data for RFD measures additional familiarisation session may be required.
Additionally, the method for detecting the onset of contraction used in the study by Haff, et al.
9 was different and this may impact reliability. Haff, et al. 9 visually identified the start point
and in this study the point was defined at the point where the force exceeded 5 SD from
baseline. Haff, et al. 9 deemed pRFD sampling windows unreliable except for pRFD 20,
however the CV was 12.9%, which would be unreliable based on the criteria set in this study.
All measures of pRFD were deemed unreliable in this study. Similar to the results of this study,
Haff, et al. 9 deemed avgRFD unreliable. Impulse at 100 ms, 200 ms and 300 ms has been
reported as reliable in previous research (ICC 0.86 and CV 8.4%) 14-16, in line with the
results of this study, except for impulse at 100 ms which was deemed unreliable.
The TE was less than the SWC0.2 for maximum force and absolute PF in both tests, and
in the IMTP, the TE of relative PF (N/kg) was less than SWC0.2 demonstrating that the test is
useful in detecting if a “meaningful change” in performance has occurred for these variables.
All other variables in both tests were rated as “marginal” or “ok”. The TE was below the
SWC0.5 for each variable for each test rating the usefulness as “good”. Where the TE is above
the SWC0.2, coaches and practitioners can use SWC0.5 to provide context of “meaningful
change” to group analysis since the SWC0.2 may lack the sensitivity.
Participants produced significantly greater absolute PF, relative PF (N/kg) and
allometrically scaled PF in the ISqT compared to the IMTP with a moderate effect size. In
addition, participants also produced significantly greater impulse (0 300 ms) with a small
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
effect size. However, when participants were split by sex, there were no significant results for
males, also having a small effect size. By comparison, significant differences were seen for
female participants for absolute PF, relative PF (N/kg) and allometrically scaled PF with a large
effect size. Results are similar to Nuzzo, et al. 11 who found that males produced an additional
12.5% relative PF (N/kg) in an ISqT. Males produced an additional 9.5% relative PF and
females produced an additional 28.5% relative PF during an ISqT compared with the IMTP.
This may be due to the elimination of the use of upper extremity force during the ISqT
compared with the IMTP, providing a potential advantage to athletes with weakness or
dysfunction in their upper extremity. Females have shown to be weaker in the upper extremity
compared to their male counterparts 24, possibly leaving females at a disadvantage in
demonstrating lower extremity strength when performing an IMTP compared to the ISqT. In
addition, participants in this study had at least 6 months of resistance training experience, and
not all were familiar with weightlifting movements. More recently, Beckham, et al. 4 noted that
those with less experience in weightlifting movements have spent less time overloading the
power position and would not be expected to show the effect of training in this position. This
lack of experience in this position may also affect the reliability results. 4
Results suggest that the IMTP and ISqT are reliable for comparable variables, with the
IMTP appearing to be more reliable when examining pRFD and the ISqT more reliable when
examining impulse. When determining the reliability the ICC and CV should be measured with
the CIs giving a clearer understanding of the level of reliability. Significant differences exist
between the IMTP and ISqT, and this difference is greater for female athletes compared to
males.
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Practical Applications
The present study demonstrated that the IMTP and ISqT are reliable for maximum
force, absolute PF, relative PF, RFD (0 200 ms and 0 250 ms) and impulse (0 300 ms).
Impulse (0 200 ms and 0 250 ms) is reliable in the ISqT. Variables of maximum force and
absolute PF are useful in detecting meaningful change in both tests (SWC0.2). Where the TE is
above the SWC0.2, coaches and practitioners can use SWC0.5 to provide context of “meaningful
changefor all other variables in both tests. Significant differences exist between the IMTP
and ISqT for measures of absolute PF, relative PF, allometrically scaled PF and impulse (0
300 ms). If coaches and practitioners are looking to measure an athlete’s true maximum
strength, the ISqT may be the preferred test, especially among female athletes. The ISqT may
be a truer reflection of the athletes maximum lower extremity strength compared with the
IMTP. Future research should determine if different knee and hip angles in the ISqT produce
higher forces than those used in this study.
Conclusions
Results suggest that the IMTP and ISqT are reliable for maximum force, absolute PF,
relative PF, RFD (0 200 ms and 0 250 ms) and impulse (0 300 ms). The ISqT may be
useful for measures of impulse. Both tests are useful in detecting the smallest worthwhile
change for maximum force and absolute PF. The ISqT produces significantly higher absolute
and relative PF among female athletes.
Acknowledgements
The authors would like to thank all athletes who participated in this study. The authors have no
conflicts that are directly relevant to the content of this article. This research is supported by
the Irish Research Council and Sport Ireland Institute.
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
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A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
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A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
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A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Figure 1: Reliability measures of the intraclass correlation coefficient of the variables attaining
an ICC > 0.8 in either the IMTP or ISqT and CV of each variable. °/* = ICC; error bars indicate
95% confidence limits. Grey shaded area = zone of acceptable reliability (ICC > 0.8). Max
force = maximum force; PF = absolute peak force; RPF (N/N) = PF relative to body weight,
N/N; RFP (N/kg) = PF relative to body mass; AlloPF = allometrically scaled PF. RFP 0 200
= rate of force development 0 200 ms sampling window; RFD 0 250 = rate of force
development 0 250 ms sampling window. Impulse 0 200 = impulse 0 200 ms sampling
window; impulse 0 250 = impulse 0 250 ms sampling window; impulse 0 300 = impulse
0 300 ms sampling window.
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Figure 2: Reliability measure of the intraclass correlation coefficient of the variables deemed
unreliable in the IMTP and ISqT (ICC < 0.8 and/or CV > 10%). /▪ =ICC; error bars indicate
95% confidence limits. Grey shaded area = zone of acceptable reliability (ICC > 0.8). A = ICC
RFD windows, B = CV%: RFD 0 150 = rate of force development 0 150 ms sampling
window RFD 0 100 = rate of force development 0 100 ms sampling window; RFD 0 90
= rate of force development 0 90 ms sampling window; RFD 0 50 = rate of force
development 0 50 ms sampling window; RFD 0 30 = rate of force development 0 30 ms
sampling window. C = ICC pRFD windows, D = CV%: pRFD 50 = peak rate of force
development 50 ms sampling window; pRFD 30 = peak rate of force development 30 ms
sampling window; pRFD 20 = peak rate of force development 20 ms sampling window; pRFD
10 = peak rate of force development 10 ms sampling window; pRFD 5 = peak rate of force
development 5 ms sampling window; pRFD 2 = peak rate of force development 2 ms sampling
window. E = ICC impulse and Zatsiorsky RFD measures, F = CV%: RC = reactivity
coefficient; IES = index of explosiveness; avgRFD = average rate of force development;
impulse 0 100 ms = impulse 0 100 ms sampling window.
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Figure 3: A, B, C and D = Individual and group mean values of the IMTP and ISqT. A =
absolute peak force, B = impulse 0 300 ms, C = RFD 0 200 ms, D = RFD 0 250 ms.
Single dots represent the mean of the two trials of each participant for each test, straight line
links to their corresponding score on the ISqT. *Significantly different using Holm’s Sequential
Bonferroni adjusted p-value, p < 0.05.
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Figure 4: Results of Hedges g with 95% CIs calculated for between tests. The shaded area
detail Cohen’s scale which was interpreted as trivial (g < 0.2), small (0.2 ≤ g < 0.5), moderate
(0.5 ≤ g < 0.8) and large (g ≥ 0.8).
95% CI
95% CI
Variables
Mean ± SD
ICC
Lower
Upper
CV%
Lower
Upper
TE
SWC
(0.2)
Rating
SWC
(0.5)
Rating
Max force (N)
2669 ± 599
0.98
0.96
0.99
3.4
2.6
4.7
89
120
good
301
good
Absolute PF (N)
1994 ± 513
0.97
0.94
0.99
4.6
3.6
6.4
89
103
good
259
good
RPF (N/N)
2.9 ± 0.4
0.93
0.84
0.97
4.6
3.6
6.4
0.1
0.1
ok
0.2
good
RPF (N/kg)
28.7 ± 4.4
0.93
0.84
0.97
4.6
3.6
6.4
1.3
0.9
good
2.2
good
AlloPF (N/kg0.67)
116 ± 20.9
0.95
0.88
0.98
4.6
3.6
6.4
5.1
4.2
marginal
10.6
good
RFD 0 200 ms (N/s)
5623 ± 1447
0.89
0.77
0.95
9.6
7.4
13.5
509
298
marginal
746
good
RFD 0 250 ms (N/s)
4919 ± 1286
0.86
0.77
0.95
9.6
7.5
13.6
458
265
marginal
663
good
Impulse 0 300 ms (N.s)
344 ± 108
0.92
0.82
0.96
9.4
8.8
16
33
22
marginal
55
good
95% CI
95% CI
Variables
Mean ± SD
ICC
Lower
Upper
CV%
Lower
Upper
TE
SWC
(0.2)
Rating
SWC
(0.5)
Rating
Max force (N)
2997 ± 784
0.98
0.96
0.99
3.5
2.7
4.8
110
147
good
368
good
Absolute PF (N)
2322 ± 709
0.97
0.94
0.99
4.6
3.6
6.4
110
131
good
327
good
RPF (N/N)
3.5 ± 0.6
0.95
0.88
0.98
4.6
3.6
6.4
0.2
0.1
marginal
0.3
good
RPF (N/kg)
33.3 ± 7.5
0.95
0.88
0.98
4.6
3.6
6.4
1.5
1.3
marginal
3.2
good
AlloPF (N/kg0.67)
134.9 ± 33.1
0.96
0.9
0.98
4.6
3.6
6.4
6.2
5.7
marginal
14.3
good
RFD 0 200 ms (N/s)
5879 ± 1891
0.91
0.8
0.96
9.9
7.7
14
578
365
marginal
911
good
RFD 0 250 ms (N/s)
5083 ± 1566
0.91
0.8
0.96
9.8
7.5
15.4
488
306
marginal
764
good
Impulse 0 200 ms (N.s)
212 ± 74
0.92
0.84
0.97
9.9
7.9
14.3
21
15
marginal
37
good
Impulse 0 250 ms (N.s)
294 ± 99
0.95
0.88
0.98
8.1
6.3
11.4
24
20
marginal
49
good
Impulse 0 300 ms (N.s)
379 ± 124
0.96
0.91
0.98
6.7
5.2
9.4
26
25
ok
62
good
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Table 3: Comparison of variables deemed reliable in the IMTP and ISqT for male and female
participants.
All Participants
95% CI
Variables
p
g
lower
upper
Absolute PF (N)
0.006*
0.52
-0.03
1.07
RPF (N/kg)
0.006*
0.74
0.18
1.30
AlloPF (N/kg0.67)
0.006*
0.67
0.11
1.23
RFD 0 200 ms (N/s)
0.708
0.15
-0.39
0.69
RFD 0 250 ms (N/s)
0.708
0.11
-0.43
0.66
Impulse 0 300 ms (N.s)
0.036*
0.30
-0.25
0.84
*Statistically different using Holm’s Sequential Bonferroni adjusted p-value, g = Hedges g for magnitude of
effect.
Table 4: Descriptive statistics for male participants and comparison of variables deemed
reliable in the IMTP and ISqT.
IMTP
ISqT
95% CI
Variables
Mean ± SD
Mean ± SD
p
g
lower
upper
Absolute PF (N)
2225 ± 493
2466 ± 761
0.222
0.37
-0.33
1.07
RPF (N/kg)
30.4 ± 3.8
33.3 ± 7.0
0.245
0.50
-0.20
1.21
AlloPF (N/kg0.67)
125 ± 18.5
137.6 ± 33
0.245
0.46
-0.25
1.16
RFD 0 200 ms (N/s)
6077 ± 1502
6044 ± 2090
1.000
-0.02
-0.71
0.68
RFD 0 250 ms (N/s)
5392 ± 1301
5297 ± 1701
1.000
-0.06
-0.75
0.63
Impulse 0 300 ms (N.s)
383 ± 119
407 ± 142
0.555
0.18
-0.52
0.87
A Comparison of the Isometric Mid-Thigh Pull and Isometric Squat: Intraday Reliability, Usefulness and the Magnitude of
Difference Between Tests” by Brady CJ et al.
International Journal of Sports Physiology and Performance
© 2017 Human Kinetics, Inc.
Table 5: Descriptive statistics for female participants and comparison of variables deemed
reliable in the IMTP and ISqT.
IMTP
ISqT
95% CI
Variables
Mean ± SD
Mean ± SD
p
g
lower
upper
Absolute PF (N)
1624 ± 285
2090 ± 578
0.042*
1.81
0.77
2.85
RPF (N/kg)
26 ± 4.1
33.4 ± 8.7
0.042*
2.06
0.98
3.15
AlloPF (N/kg0.67)
101.6 ± 16.3
130.6 ± 34.6
0.042*
2.07
0.98
3.15
RFD 0 200 ms (N/s)
4895 ± 1049
5614 ± 1589
0.156
1.10
0.16
2.04
RFD 0 250 ms (N/s)
4162 ± 857
4741 ± 1335
0.156
1.05
0.11
1.98
Impulse 0 300 ms (N.s)
283 ± 46
333 ± 75
0.051
1.28
0.32
2.25
*Statistically different using Holm’s Sequential Bonferroni adjusted p-value, g = Hedges g for magnitude of
effect.
... Given the importance of force production in athletic activities, sport scientists and applied practitioners routinely assess force capabilities using a variety of physical tests [1,2]. In particular, tests involving maximal voluntary isometric contractions [1,[3][4][5] are commonly implemented due to their high reliability [4,[6][7][8][9], ease to be administered [1,4,10], time efficiency [4] and minimal skill requirement [1,4]. Two isometric tests frequently used in exercise and sport science settings are the isometric mid-thigh pull (IMTP) and the isometric squat (ISQT) tests [4][5][6]9]. ...
... In particular, tests involving maximal voluntary isometric contractions [1,[3][4][5] are commonly implemented due to their high reliability [4,[6][7][8][9], ease to be administered [1,4,10], time efficiency [4] and minimal skill requirement [1,4]. Two isometric tests frequently used in exercise and sport science settings are the isometric mid-thigh pull (IMTP) and the isometric squat (ISQT) tests [4][5][6]9]. Both are reliable [4,[6][7][8][9]11], are correlated with athletic performance indices, such as jump height (e.g., absolute and body mass relative gross peak force outputs across time intervals ranging from 50 ms to 300 ms) [11][12][13][14], sprint times over distances from 5 m to 20 m (e.g., absolute net peak force and peak rate of force development outputs as well as rate of force development variables expressed both as peak values and across time intervals ranging from 30 ms to 100 ms) [11][12][13]15] and change of direction times (peak gross force and peak rate of force The isometric horizontal push test correlates with jumping and sprinting performance among athletes and recreationally active controls the body orientation in the IHPT is partly similar to that an athlete assumes prior to performing horizontal jumps and short-sprint tasks, which presumes kinetic responses similar to these athletic tasks [18,19,31]. ...
... Two isometric tests frequently used in exercise and sport science settings are the isometric mid-thigh pull (IMTP) and the isometric squat (ISQT) tests [4][5][6]9]. Both are reliable [4,[6][7][8][9]11], are correlated with athletic performance indices, such as jump height (e.g., absolute and body mass relative gross peak force outputs across time intervals ranging from 50 ms to 300 ms) [11][12][13][14], sprint times over distances from 5 m to 20 m (e.g., absolute net peak force and peak rate of force development outputs as well as rate of force development variables expressed both as peak values and across time intervals ranging from 30 ms to 100 ms) [11][12][13]15] and change of direction times (peak gross force and peak rate of force The isometric horizontal push test correlates with jumping and sprinting performance among athletes and recreationally active controls the body orientation in the IHPT is partly similar to that an athlete assumes prior to performing horizontal jumps and short-sprint tasks, which presumes kinetic responses similar to these athletic tasks [18,19,31]. However, additional steps are currently required to establish the utility of the IHPT. ...
Article
The aim of this study was two-fold: (i) to examine the relationships between force outputs measured in the isometric horizontal push test (IHPT) and athletic performances; (ii) to compare IHPT outputs between football players and recreationally active controls. Thirty-two male subjects (football players, n = 16; university students, n = 16) completed the IHPT, countermovement jump (CMJ), standing long jump (SLJ), 5 m, 10 m and 20 m sprint tests, randomly across two testing sessions. Multivariate linear regression analysis was used to examine the relationships between IHPT outputs and athletic performances by accounting for the subjects' athletic background. An independent sample t-test was used to compare the IHPT outputs between groups. Moderate to very strong linear relationships (r2 range: 0.16-0.56) were found between the IHPT and all athletic performances (all p < .026). Percent variance explained by the IHPT outputs after accounting for groups difference was 16%, 56%, 54%, 48% and 40% for CMJ height, SLJ distance, 5 m, 10 m and 20 m sprint performances, respectively. Compared to controls (6.18 ± 0.89 N/kg), football players (10.09 ± 1.57 N/kg) achieved greater IHPT force outputs (p < .001, Hedges' g = 3.2, large ES). The IHPT is clearly correlated to horizontal and vertical athletic performances and can adequately distinguish between athletes and recreationally active controls based on their IHPT results. Future studies should examine the usefulness of the IHPT as a testing tool informing training prescription and performance monitoring practices.
... The PF provides a measure of maximal strength during an isometric voluntary contraction (Maffiuletti et al., 2016). Previous studies reported that athletes, especially the females, during ISqT procedures generated higher amounts of PF, compared to IMTP performed at the same knee and hip angles (140 o ) (Nuzzo et al., 2008;Brady et al., 2018;Silva et al., 2020). This difference may be exhibited due to the position of the bar height that allows athletes producing maximal force. ...
... The aim of this study was to compare the vertical PF and the relative vertical PF achieved during the IMTP and ISqT tests when they are performed at the same knee and hip angles, in elite level track and field athletes. Our main finding confirms recent observations of higher PF and relative PF expressions during the ISqT test compared to IMTP (Brady et al., 2018;Silva et al., 2020) with the magnitude of these differences being large. Therefore, the ISqT may be more appropriate testing procedure for identifying an athlete's maximum strength capacity compared to the IMTP. ...
... Both tests were performed at the same knee and hip angles (140°) and therefore the only difference between the two isometric tests was the position of the bar height that allowed athletes producing maximal force. The higher PF is probably associated with the elimination of the use of upper extremity force during the ISqT, providing a potential advantage to athletes with weakness in their upper extremity (Brady et al., 2018). Furthermore, higher PF during ISqT procedure may be attributed to bar position as this is likely a determinant moderator of the loading requirements in each individual exercise, influencing the kinetic, kinematic and muscle activation patterns (Ebben et al., 2009). ...
Conference Paper
Full-text available
The aim of this study was to compare the vertical peak force (PF) generated during the isometric mid-thigh pull (IMTP) and isometric squat (ISqT) performed at the same knee and hip angles. Fourteen elite track and field athletes performed 3 maximal efforts of isometric IMTP and ISqT tests. The vertical PF was measured by a force platform (Kistler 9290CD, AG Winterthur, Switzerland). Our findings revealed significant higher PF and relative PF during ISqT than IMTP (Mean difference: 953 ± 224 N, p < 0.001, d = 1.62 and 14.6 ± 2.4 N·kg-1 , p < 0.001, d = 3.8, respectively). The results of this study suggest that ISqT may be more appropriate testing procedure for identifying athletes' maximum isometric strength capacities in elite track and field athletes.
... Across all men, absolute vGRF observed during the bilateral squat aligns with those reported in male Division 1 football and track and field athletes (Nuzzo et al., 2008) and is ~500-1000 N greater than that of collegiate rugby union players, distance runners, and amateur boxers (Brady et al., 2020). For all women, absolute vGRF observed during the bilateral squat was comparable to those reported across various sports (Brady et al., 2018). Only two studies have investigated absolute vGRF during the unilateral squat, reporting values ~1000-1500 N lower than that observed in the present study (Beckman et al., 2014;Bishop et al., 2019). ...
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This study aimed to investigate the within-and between-session reliability, variability, and minimal detectable change (MDC) of vertical ground reaction force (vGRF) during bilateral and unilateral lower extremity maximal isometric force tests. Eighteen participants (men: n = 9, age: 27.9 ± 6.3 y, height: 1.82 ± 0.06 m, mass: 82.4 ± 10.4 kg, strength training experience: 10.4 ± 7.7 y; women: n = 9, age: 29.3 ± 8.6 y, height: 1.68 ± 0.01 m, mass: 58.0 ± 5.8 kg, strength training experience: 5.5 ± 3.6 y) attended two data collection sessions separated by 48 h. The absolute, net, and relative vGRF were calculated across bilateral and unilateral variations of the squat, standing plantarflexion, and seated plantarflexion positions. All measures of vGRF demonstrated excellent reliability and low variability within (intraclass correlation coefficients (ICC): 0.92-0.99; coefficient of variation (CV): 2.9-6.5%) and between sessions (ICC: 0.95-1.00; CV: 2.0-6.0%), across all positions. The MDC ranged between 135-276 N (5.1-14.5%), with the seated plantarflexion positions demonstrating the highest values as a percentage of the group mean (13.3-14.5%). Maximal isometric force testing during bilateral and unilateral variations of the squat, standing plantarflexion, and seated plantarflexion positions provides reliable measurement of vGRF in men and women.
... The familiarization session allows the subjects to learn the protocol, thus, becoming comfortable with the study design in subsequent sessions. Moreover, recent research acknowledges the importance of evaluating the effects of familiarization rather than just stating that familiarizations sessions were held [6][7][8][9]. ...
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... A recent study by Nimphius et al. [12] indicated no difference in muscle activity between strength-matched males and females. It should be noted that the IMTP peak force values reported in this study are lower than those reported in an excellent review of the literature by Brady et al. [42] Rather than either the male group being relatively weak, or the female group being relatively strong, it appears both subject groups within the current study were relatively weaker compared to male and female subject values from previous works. Thus, the findings of the current study should be interpreted with the athlete population, methodology, and method of calculating variables in mind when comparing normative data across research. ...
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The purpose of this study was to compare countermovement jump force–time measures between strength-matched male and female soccer players. Males (n = 11) and females (n = 11) were strength-matched via isometric mid-thigh pull testing, whereby peak force values were normalised to body mass. Subjects performed three maximal-effort countermovement jumps (CMJs) on a force platform from which a range of kinetic and kinematic variables were calculated via forward dynamics. Thereafter, differences in gross measures were examined via independent t-tests, while differences in force–, power–, velocity–, and displacement–time curves throughout the entire CMJ were analysed using statistical parametric mapping (SPM). Jump height, reactive strength index modified, propulsion mean force, propulsion impulse, and propulsion mean velocity were all greater for males (d = 1.50 to 3.07). Relative force– and velocity–time curves were greater for males at 86–93% (latter half of the concentric phase) and 85–100% (latter half of the concentric phase) of normalized movement time, respectively. Time to take-off, braking phase time, braking mean velocity and impulse, propulsion phase time and centre of mass displacement were similar between males and females (d = −0.23 to 0.97). This research demonstrates the strength of SPM to identify changes between entire force-time curves. Continued development and the use of SPM analysis could present the opportunity for a refined comparison of strength-matched male and female CMJ performance with the analysis of entire force–time curves.
... The starting point for RFD calculations was set at 3 x SD of the baseline's force (Brady et al., 2018;De Ruiter et al., 2006;. Figures 1a and 1b show an example of RFD calculations for the ILP and the SJ. ...
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Research has demonstrated a clear relationship between dynamic strength and vertical jump performance; however, the relationship of isometric strength and vertical jump performance has been studied less extensively. The aim of this study was to determine the relationship between isometric strength and performance during the squat jump (SJ) and countermovement jump (CMJ). Twenty-two male collegiate athletes (mean ± SD; age = 21.3 ± 2.9 years; height = 175.63 ± 8.23 cm; body mass = 78.06 ± 10.77 kg) performed isometric mid-thigh pulls (IMTP) to assess isometric peak force (IPF), maximum rate of force development (mRFD) and impulse (I100, I200, and I300). Force time data, collected during the vertical jumps, was used to calculate peak velocity (PV), peak force (PF), peak power (PP), and jump height. Absolute IMTP measures of IMP showed the strongest correlations with VJ PF(r = 0.43 - 0.64, p ≤ 0.05), and VJ PP (r = 0.38 - 0.60, p ≤ 0.05). No statistical difference was observed in CMJ height (0.33 ± 0.05 m vs. 0.36 ± 0.05 m; p = 0.19; ES = -0.29) and SJ height performance (0.29 ± 0.06 m vs. 0.33 ± 0.05 m vs.; p = 0.14; ES = -0.34) when comparing stronger to weaker athletes. The results of this study illustrate that absolute IPF and IMP are related to VJ PF and PP, but not VJ height. As stronger athletes did not jump higher than weaker athletes, dynamic strength tests may be more practical methods of assessing the relationships between relative strength levels and dynamic performance in collegiate athletes.
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Verbal instructions play a key role in motor learning and performance. Whereas directing one's attention towards bodily movements or muscles (internal focus) tends to hinder performance, instructing persons to focus on the movement outcome, or an external object related to the performed task (external focus) enhances performance. The study's purpose was to examine if focus of attention affects maximal force production during an isometric mid-thigh pull (IMTP) among 18 trained athletes (8F & 10M). Athletes performed three IMTP trials a day for three consecutive days. The first day was a familiarization session in which athlete's received only control instructions. The following two days athletes received either control, internal or external focus of attention instructions in a randomized, within-subject design. Compared to performance with an internal focus of attention, athletes applied 9% greater force when using an external focus of attention (P< 0.001; effect size [ES] = 0.33) and 5% greater force with control instructions (P= 0.001; ES= 0.28). A small positive 3% advantage was observed between performances with an external focus of attention compared to control instructions (P= 0.03; ES= 0.13). Focusing internally on body parts and/or muscle groups during a movement task that requires maximal force hinders performance, whereas focusing on an object external to the self leads to enhanced force production, even when using a simple multi joint static task such as the IMTP. Copyright (C) 2015 by the National Strength & Conditioning Association.