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Fiabilidade e influência da instrução e modalidade de exercício na taxa de produção de força dos flexores dos joelhos
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Objetivos: (1) Determinar a fiabilidade intra-dia da medida da taxa de produção de força (TPF) dos
flexores do joelho, na posição de decúbito ventral, nas seguintes condições de teste: i) realizando a
contração unilateralmente ou bilateralmente; e ii) com uma instrução prévia mencionando “rápido e
forte” ou “rápido”. (2) Verificar se a TPF é diferente entre modalidades de instrução, tipo de exercício
e membros dominante e não-dominante.
Método: Catorze sujeitos (27,3 ± 6 anos; 174 ± 0,4 cm; 73 ± 8,4 kg) sem historial de lesão nos
isquiotibiais realizaram duas sessões de testes, separados por uma hora. Em cada sessão, realizaram 2
séries de 3 repetições de flexão isométrica do joelho de forma unilateral, e 2 séries de 3 repetições de
forma bilateral. Em cada um dos tipos de exercício, e antes de uma série de repetições, foi aplicada a
instrução “rápido”, e noutra série a instrução “rápido e forte''. As instruções foram aplicadas com
ordem aleatória, e os testes realizados com recurso a feedback visual, na posição decúbito ventral e
com os joelhos fletidos a 30º, num equipamento com células de força embutidas associadas a cada um
dos membros. Os dados foram processados utilizando rotinas Matlab. Como critério de momento de
início da TPF foi considerado o valor de 3 desvios padrão da linha de base de força detectado de
forma automatizada. Para determinação da fiabilidade intra-sessão, foi calculado o coeficiente de
correlação intraclasse (ICC) e coeficiente de variação (CV). Para se examinar a influência dos fatores
instrução, exercício e membro, foi aplicado o teste de análise de variância de três fatores com medidas
repetidas. A análise foi realizada para as seguintes janelas temporais: 0-50ms, 0-100-ms, 50-100ms e
100-200ms.
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Resultados: A maioria dos testes de TPF mostraram fiabilidade intra-dia classificada que variou entre
moderada a excelente (ICC=0.52-0.91; CV=6%-16%), com exceção do teste TPF realizado de forma
bilateral com a instrução “rápido”, no membro direito, na janela 100- 200 ms (ICC = 0.40, IC 95% =
-0.17-0.76; CV= 12% ±13% ). Nenhum efeito foi observado para as interações entre fatores exercício,
instrução e membro. Porém, observou-se um efeito do fator instrução no desempenho da TPF na
janela temporal 0-100 ms (p = 0.049), bem como um efeito do fator exercício no desempenho e da
TPF na janela temporal 100-200 ms (p < 0.001).
Conclusões: A quantificação da TPF nos flexores do joelho aparenta ser fiável, quer avaliada com
exercício unilateral ou bilateral, ou com diferentes tipos de instruções (i.e. “rápido” e “rápido e
forte”). Adicionalmente, e na sua generalidade, a modalidade de exercício (i.e. unilateral vs. bilateral)
e tipo de instrução aparenta não afetar o desempenho da TPF, assim como aparenta não existirem
diferenças entre membros dominante e não-dominante.
Objective: (1) To determine the intra-day reliability of the measurement of the force rate of force development (RFD) of the knee flexors, in the prone position, under the following test conditions: i) performing the contraction unilaterally or bilaterally; and ii) with a prior instruction mentioning “fast and strong” or “fast”. (2) Verify whether the RFD will differ between instructions, exercise type, and dominant and non-dominant members. Method: Fourteen subjects (27.3 ± 6 years; 174 ± 0.4 cm; 73 ± 8.4 kg) with no history of hamstring injury performed two testing sessions one hour apart. In each session, they performed 2 sets of 3 repetitions of isometric knee flexion unilaterally, and 2 sets of 3 repetitions bilaterally. In each of the types of exercise, and before a set of repetitions, the instruction “fast” was applied, and in another set the instruction “fast and strong''. The instructions were performed using visual feedback, and in random order. The tests were performed in the prone position and with the knees flexed at 30º, in an equipment with built-in force cells associated with each of the limbs. Data was processed using Matlab routines. The RFD onset time (i.e. onset) of all repetitions was determined based on a threshold of 3 standard deviations from the strength baseline, detected in an automated way. To determine the intra-session reliability, the intra-class correlation coefficient (ICC) and coeffiecient of variation (CV) were calculated; and to examine the influence of the factors instruction, exercise, and member factors, a three-way repeated measures ANOVA was applied. Results: Most of the RFD tests showed an intra-day reliability that ranged from moderate to excellent (ICC=0.52-0.91; CV=6%-16%), with the exception of the RFD test performed bilaterally with the 12 instruction “fast”, in the right limb, in the 100-200 ms window (ICC = 0.40, 95% CI = -0.17-0.76; CV= 12% ±13%). No effect was observed for interactions between exercise, instruction, and limb factors. However, there was an effect of the instruction factor on RFD performance in the 0-100 ms time window (p = 0.049), as well as an effect of the exercise factor on performance and RFD in the 100-200 ms time window (p < 0.001 ). Conclusions: The quantification of RFD in the knee flexors appears to be reliable, whether assessed with unilateral or bilateral exercise, or with different types of instructions (i.e. “fast” and “fast and strong”). Additionally, and in general, the exercise modality (i.e. unilateral vs. bilateral) and type of instruction do not seem to affect the performance of the RFD, as there appears to be no difference between dominant and non-dominant limbs.
Objective: (1) To determine the intra-day reliability of the measurement of the force rate of force development (RFD) of the knee flexors, in the prone position, under the following test conditions: i) performing the contraction unilaterally or bilaterally; and ii) with a prior instruction mentioning “fast and strong” or “fast”. (2) Verify whether the RFD will differ between instructions, exercise type, and dominant and non-dominant members. Method: Fourteen subjects (27.3 ± 6 years; 174 ± 0.4 cm; 73 ± 8.4 kg) with no history of hamstring injury performed two testing sessions one hour apart. In each session, they performed 2 sets of 3 repetitions of isometric knee flexion unilaterally, and 2 sets of 3 repetitions bilaterally. In each of the types of exercise, and before a set of repetitions, the instruction “fast” was applied, and in another set the instruction “fast and strong''. The instructions were performed using visual feedback, and in random order. The tests were performed in the prone position and with the knees flexed at 30º, in an equipment with built-in force cells associated with each of the limbs. Data was processed using Matlab routines. The RFD onset time (i.e. onset) of all repetitions was determined based on a threshold of 3 standard deviations from the strength baseline, detected in an automated way. To determine the intra-session reliability, the intra-class correlation coefficient (ICC) and coeffiecient of variation (CV) were calculated; and to examine the influence of the factors instruction, exercise, and member factors, a three-way repeated measures ANOVA was applied. Results: Most of the RFD tests showed an intra-day reliability that ranged from moderate to excellent (ICC=0.52-0.91; CV=6%-16%), with the exception of the RFD test performed bilaterally with the 12 instruction “fast”, in the right limb, in the 100-200 ms window (ICC = 0.40, 95% CI = -0.17-0.76; CV= 12% ±13%). No effect was observed for interactions between exercise, instruction, and limb factors. However, there was an effect of the instruction factor on RFD performance in the 0-100 ms time window (p = 0.049), as well as an effect of the exercise factor on performance and RFD in the 100-200 ms time window (p < 0.001 ). Conclusions: The quantification of RFD in the knee flexors appears to be reliable, whether assessed with unilateral or bilateral exercise, or with different types of instructions (i.e. “fast” and “fast and strong”). Additionally, and in general, the exercise modality (i.e. unilateral vs. bilateral) and type of instruction do not seem to affect the performance of the RFD, as there appears to be no difference between dominant and non-dominant limbs.
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Bilateral Contração isométrica voluntária máxima Feedback Instrução verbal Rápido Rápido e forte Reprodutibilidade Unilateral Verbal instruction Unilateral Feedback Reliability Maximum voluntary isometric contraction Fast Fast and strong