Title

The influence of barbell and body position on force-time characteristics in the isometric mid-thigh pull

Author Identifiers

Stuart Nathan Guppy
ORCID: 0000-0001-9209-7409

Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Medical and Health Sciences

First Advisor

Professor G. Gregory Haff

Second Advisor

Dr Nikolo Media

Field of Research Code

11

Abstract

Publication 1: The Isometric Mid-Thigh Pull: A Review and Methodology – Part 1 Isometric tests are commonly used to monitor physical qualities that underpin athletic performance. As single-joint laboratory-based tests display poor relationships to the multi-joint movements found in sport, multi-joint isometric tests like the isometric midthigh pull (IMTP) are commonly used instead. Force-time characteristics in these multijoint tests typically display stronger relationships to dynamic performance, particularly in the case of the isometric mid-thigh pull. As such this review focuses on the relationships between force-time characteristics in the IMTP and dynamic athletic performance.

Publication 2: The Isometric Mid-Thigh Pull: A Review & Methodology – Part 2 The isometric mid-thigh pull (IMTP) is a commonly used test for the assessment of skeletal muscle function in athletes from a wide variety of sports. Although forcegenerating capacity and rate of force development measured in the IMTP are related to dynamic athletic performance measures, the testing and analysis procedures used can have adverse effects on the magnitude and reliability of the force-time characteristics produced. As such, this review focuses on the correct testing and analysis methodologies to use during IMTP testing.

Publication 3: The Effect of Altering Body Posture and Barbell Position on the Within- Session Reliability and Magnitude of Force-Time Curve Characteristics in the Isometric Mid-Thigh Pull

A large degree of variation in the position used during isometric mid-thigh pull (IMTP) testing, and conflicting results of the effects of these changes, can be found in the literature. This study investigated the effect of altering body posture and barbell position on the reliability and magnitude of force-time characteristics generated during the IMTP. Seventeen strength-power athletes (n = 11 males, height: 177.5 ± 7.0 cm, body mass: 90 ± 14.1 kg, age: 30.6 ± 10.4 years; n = 6 females, height: 165.8 ± 11.4 cm; body mass: 66.4 ± 13.9 kg, age: 30.8 ± 8.7 years) with greater than 6 months of training experience in the clean (1RM: 118.5 ± 20.6 kg, 77.5 ± 10.4 kg) volunteered to undertake the experimental protocol. Subjects performed the IMTP using four combinations of hip and knee angles, and two different barbell positions. The first barbell position corresponded to the second pull of the clean, while the second rested at the mid-point between the iliac crest and the patella. Peak force (PF), time-specific force (F50, F90, F150, F200, F250), peak rate of force development (pRFD), and impulse (IMP) time-bands were reliable in all four testing positions examined. Statistically greater PF, F50, F90, F150, F200, F250, pRFD and IMP0-50, IMP0-90, IMP0-150, and IMP0-200 were generated in a testing position corresponding to the second pull of the clean when compared to a bent over torso angle, regardless of the barbell position used. Moderate to large effect sizes favouring a testing position corresponding to the second pull were also found. Overall, when performing the IMTP, an upright torso and a barbell position that matches the second pull of the clean should be used.

Publication 4: The Effect of Altering Body Posture and Barbell Position on the Between- Session Reliability of Force-Time Curve Characteristics in the Isometric Mid-Thigh Pull

Seventeen strength and power athletes (n = 11 males, 6 females; height: 177.5 ± 7.0 cm, 165.8 ± 11.4 cm; body mass: 90.0 ± 14.1 kg, 66.4 ± 13.9 kg; age: 30.6 ± 10.4 years, 30.8 ± 8.7 years), who regularly performed weightlifting movements during their resistance training programs, were recruited to examine the effect of altering body posture and barbell position on the between-session reliability of force-time characteristics generated in the isometric mid-thigh pull (IMTP). After subjects were familiarised with the testing protocol, they undertook two testing sessions which were separated by seven days. In each session, the subjects performed three maximal IMTP trials in each of the four testing positions examined, with the testing order randomised. In each position, no significant differences were found between-sessions for all force-time characteristics (p = >0.05). Peak force (PF), time-specific force (F50, F90, F150, F200, F250), and IMP time-bands (0-50, 0-90, 0- 150, 0-200, 0-250 ms) were reliable across each of the four testing positions (ICC ³0.7, CV £15%). Time to peak force, peak RFD, RFD time-bands (0-50, 0-90, 0-150, 0-200, 0-250), and peak IMP were unreliable regardless of testing position used (ICC = <0.7, CV = >15%). Overall, the use of body postures and barbell positions during the IMTP that do not correspond to the second pull of the clean have no adverse effect of the reliability of the force-time characteristics generated.

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