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1.
Sports Biomech ; 19(1): 1-25, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29781788

RESUMO

The use of isometric strength testing, particularly the isometric mid-thigh pull (IMTP) has increased dramatically over the last decade. The IMTP and isometric squat (ISqT) provide one aspect of performance monitoring with variables such as peak force and rate of force development being derived from the force-time curve. The reliability of some of these variables is conflicting in the literature, and the reporting of the reliability is not standardised across the research. The majority of research only reports intraclass correlation coefficients with very few studies reporting coefficient of variation and 90% confidence intervals. Additionally, methods used to calculate variables from the force-time curve differ across studies. An aim of muscle strength testing is to provide normative values for specific sports, allowing coaches to distinguish between performance levels or evaluate the effects of training on performance. This narrative review aims to evaluate studies that have researched the reliability and/or reported normative data for both tests. Additionally, the testing protocols and the force-time curve analysis techniques utilised are discussed, concluding with practical applications for coaches on the uses and limitations of these tests. Results demonstrate that peak force is the most reliable measure and can be used to determine maximum strength capabilities.


Assuntos
Teste de Esforço/métodos , Força Muscular/fisiologia , Coxa da Perna/fisiologia , Levantamento de Peso , Fenômenos Biomecânicos , Humanos , Contração Isométrica/fisiologia , Valores de Referência , Reprodutibilidade dos Testes , Esportes/fisiologia
2.
J Strength Cond Res ; 33(12): 3252-3262, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31269001

RESUMO

Guppy, SN, Brady, CJ, Kotani, Y, Stone, MH, Medic, N, and Haff, GG. Effect of altering body posture and barbell position on the within-session reliability and magnitude of force-time curve characteristics in the isometric midthigh pull. J Strength Cond Res 33(12): 3252-3262, 2019-A large degree of variation in the position used during isometric midthigh 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: 90.0 ± 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 (1 repetition maximum: 118.5 ± 20.6 kg, 77.5 ± 10.4 kg) volunteered to undertake the experimental protocol. Subjects performed the IMTP using 4 combinations of hip and knee angles, and 2 different barbell positions. The first barbell position corresponded to the second pull of the clean, while the second rested at the midpoint between the iliac crest and the patella. Peak force (PF), time-specific force (F50, F90, F150, F200, and F250), peak rate of force development (pRFD), and impulse (IMP) time bands were reliable in all 4 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 with a bent over torso angle, regardless of the barbell position used. Moderate to large effect sizes favoring 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.

3.
Int J Sports Physiol Perform ; : 1-8, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-30958061

RESUMO

PURPOSE: To examine the relationships between the isometric midthigh pull (IMTP), isometric squat (ISqT), and sprint acceleration performance in track-and-field sprinters and to determine whether there are differences between men and women. METHODS: Fifteen male and 10 female sprinters performed 3 maximal-effort IMTPs, ISqTs, and 3 × 30-m sprints from blocks. RESULTS: Among the men, the results showed significant negative correlations between IMTP and ISqT peak force; relative peak force; force at 100, 150, and 200 ms; rate of force development (0-150 and 0-200 ms); and impulse (0-200 ms) and 0- to 5-m time (r = -.517 to -.714; P < .05). IMTP impulse (B = -0.582, P = .023) and ISqT relative peak force (B = -0.606, P = .017) significantly predicted 0- to 5-m time. Among the women, no IMTP or ISqT variables significantly correlated with any sprint times. Men measured significantly higher than women for all IMTP measures except relative peak force. Men were significantly faster than women at all splits. When comparing measures of the ISqT, there were no significant differences between men and women. CONCLUSIONS: Variables measured during the IMTP and ISqT significantly correlated with 0- to 5-m sprint performance in male athletes. Isometric strength can have a sizable influence on 0- to 5-m time, but in some cases, the maximum effect could be very small.

4.
J Strength Cond Res ; 33(3): 626-632, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30789857

RESUMO

Comyns, TM, Brady, CJ, and Molloy, J. Effect of attentional focus strategies on the biomechanical performance of the drop jump. J Strength Cond Res 33(3): 626-632, 2019-Motor performance can be influenced by focusing an athlete's attention through the use of verbal instructions. There is limited research on the effect of internal, neutral, and external attentional focus strategies on drop jump (DJ) performance aimed at maximizing height jumped (HJ) and minimizing ground contact time (CT). The purpose of this study was to assess the effect of attentional focus strategies on biomechanical variables related to efficient DJ performance, namely HJ, CT, reactive strength index (RSI), leg-spring stiffness, and peak and relative peak ground reaction force (GRF). Seventeen male recreationally trained subjects performed 2 DJs after listening to instructions designed to evoke an internal, external, or neutral attentional focus. In total, 6 DJs were performed in the testing session, and the order of the instructions was randomly assigned. Significance was set at p ≤ 0.05. Results indicated that, compared with the neutral strategy, the external focus resulted in significantly higher RSI (p = 0.046), peak GRF (p = 0.025), relative GRF (p = 0.02), and leg-spring stiffness (p = 0.02). No significant difference was seen in DJ CT and HJ between all 3 conditions (p ≥ 0.05). These results indicate that the use of an external focus of attention may potentially result in a more effective and efficient fast stretch-shortening cycle performance because of the augmentation of RSI and leg stiffness. More research is warranted, however, because of the lack of significant results pertaining to CT and HJ.


Assuntos
Atenção/fisiologia , Movimento/fisiologia , Desempenho Psicomotor , Adulto , Desempenho Atlético , Fenômenos Biomecânicos , Humanos , Masculino , Força Muscular , Distribuição Aleatória , Adulto Jovem
5.
Sports (Basel) ; 6(4)2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30513606

RESUMO

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 participants were familiarised with the testing protocol, they undertook two testing sessions which were separated by seven days. In each session, the participants performed three maximal IMTP trials in each of the four testing positions examined, with the order of testing randomized. 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 ≥ 0.7, CV ≤ 15%). Time to peak force, peak RFD, RFD time-bands (0⁻50, 0⁻90, 0⁻150, 0⁻200, 0⁻250 ms) and peak IMP were unreliable regardless of the 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 on the reliability of the force-time characteristics generated.

6.
Int J Sports Physiol Perform ; 13(7): 844-852, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-29182457

RESUMO

PURPOSE: To examine the reliability and usefulness of the isometric midthigh 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 (age, 23.6 [4.3] y; height, 1.75 [0.07] m; and body mass, 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 (0-200 and 0-250 ms), and impulse (0-300 ms) were deemed reliable (intraclass correlation coefficient [ICC] ≥.86 and coefficient of variation [CV] ≤9.4%) in the IMTP and ISqT based on predetermined criteria (ICC ≥.8 and CV ≤10%). Impulse (0-200 and 0-250 ms) was reliable in the ISqT (ICC ≥.92 and CV ≤9.9%). Participants produced significantly (P < .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 = .042) during the ISqT, with no significant differences among male participants (P = .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.


Assuntos
Teste de Esforço/métodos , Adulto , Estudos Transversais , Feminino , Quadril/fisiologia , Humanos , Contração Isométrica , Joelho/fisiologia , Masculino , Força Muscular/fisiologia , Reprodutibilidade dos Testes , Fatores Sexuais , Coxa da Perna/fisiologia , Adulto Jovem
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