Printer Friendly

Bilateral deficit in maximal isometric knee extension in trained men.

INTRODUCTION

The American College of Sports Medicine (2) recommends a program of regular exercise that includes cardiorespiratory, resistance, flexibility, and neuromotor exercise training. The organization believes the training program goes beyond activities of daily life, and that it is essential for most adults if they are to improve and maintain physical fitness and health. When included in a physical activity program, the resistance training (RT) part promotes increase in strength, muscle hypertrophy, and flexibility. The program assists in the maintenance of body composition and cardiovascular function, and it decreases the risks associated with coronary diseases (3,4). For the RT prescription, some variables can be manipulated as the volume of training (6), the number of sets (5), the number of repetitions (7), the load of training (1,21), the rest interval between sets (19), the exercise order (23), and the form of execution (10,18).

Thus, RT can be carried out unilaterally or in bilaterally form. Previous studies have shown that the sum of unilateral strength is greater than bilateral strength. It is reported as bilateral deficit (12,13,17). However, when the sum of the unilateral strength is lower than the bilateral strength, it is reported as bilateral facilitation (8,14,22). According to some research findings (14,16,22), such difference called bilateral deficit resulting in a lower production of strength, can be associated with reduced stimulation of motor units, neural recruiting differentiated by the crossed effect in the extra-pyramidal tract, fiber differences in the limbs, and predominance of use of one limb over the other.

Many studies have been conducted with the purpose to investigate the bilateral deficit and facilitation during RT. Some authors reported bilateral deficit in RT (8,17), while others have reported bilateral facilitation in RT (14). Interestingly, Simao and colleagues (22) reported elbow flexion bilateral deficit for muscle power, but bilateral facilitation for maximum load on one repetition maximum (1 RM). These discrepancies can be explained due to the different methodological designs of studies that were used: trained (8) and untrained subjects (12); isometric (17) and isotonic muscle contractions (8); upper limbs (22) and lower limbs exercises (12); subjects of both genders (9); and only males (13) and only females (14). Given the inconsistency in the literature, the purpose of this study was to test the hypothesis that bilateral deficit occurs in maximal isometric knee extension in trained men.

METHODS

Subjects

For convenience, 27 healthy men (25.1 [+ or -] 8.6 yrs) participated in this study. The inclusion criterion was physically active subjects with previous experience in RT for 6 months. We excluded from the sample subjects with any limitation that could interfere in the experimental procedures and/or who had positively answered one of the questions on the Physical Activity Readiness Questionnaire PAR-Q (20). All subjects were instructed to keep their daily habits and not to practice physical exercises 24 hrs prior to the tests. Each subject read and signed a specific informed consent form after being informed of the study protocol. The university institutional review board approved all the study procedures.

Procedures

Anthropometry

The subjects' body weight was assessed using a digital weighing scale (Fillizola[R], Brazil). Height was determined using a stadiometer with mm precision (Sanny[R], Brazil). Then, body mass index (BMI) was calculated.

Tests

For the tests of maximal voluntary isometric contraction, a mechanic dynamometer (Cefise[R], Brasil), previously calibrated, was fixated to extension chair equipment (Righetto[R], High On, Brazil). The 120[degrees] of angulation of knee extension was individually adjusted through a metallic goniometer (Cardiomed[R], Brazil). The dynamometer was connected to a computer which transferred the data with 1 Newton (N) of resolution to the software N2000PRO[R] (Cefise[R], Brazil).

The tests were conducted randomly in one day (unilateral and bilateral). For the unilateral test, the subjects performed 5 sec of maximal voluntary contraction with the dominant leg and immediately after with the non-dominant leg. For the bilateral test, the subjects performed 5 sec of maximal voluntary contraction with both legs. A period of 5 min of rest interval was required between the tests. To minimize error during the evaluations, the following strategies were adopted (24): (a) standardized instructions concerning the testing procedure were given to the subjects before the tests; (b) the subjects received standardized instructions on specific exercise technique; (c) the RT machine was adjusted individually for each participant; and (d) verbal encouragement was provided during the testing procedure.

Statistical Analyses

The Shapiro-Wilk normality test and a homoscedasticity test (Levene's test) were used to analyze the normal distribution of the data. All variables presented a normal distribution and homoscedasticity. The Student's paired t test was used to test the difference between the unilateral and bilateral contractions. The significance level adopted was P < 0.05. The SPSS statistical package version 19 for Windows (SPSS Inc., Chicago, USA) was used for all statistical analysis.

RESULTS

Table 1 shows the characteristics of the subjects. No significant differences were obtained between the dominant and non-dominant leg on maximum strength (P=0.600) (Table 2). Figure 1 shows a moderated correlation between the dominant and non-dominant leg strengths ([R.sup.2]=0.74; P < 0.001) Figure 2 shows that the sum of unilateral contractions (718.8 [+ or -] 106.3 N) was greater than the bilateral contraction (663.2 [+ or -] 97.7 N) (P=0.0012).

DISCUSSION

The purpose of this study was to verify if bilateral deficit occurs during maximal isometric knee extension. The results confirmed our initial hypothesis that the sum of unilateral strength is greater than the bilateral strength at 120[degrees] of knee extension in trained men. Several studies are in agreement with our findings. The study that most resembles our research design is that of Pinto et al. (17), in which the authors assessed the maximal isometric knee extension in 10 untrained men. The results showed the existence of bilateral deficit in strength, which corroborates with the results of this study. Other authors also confirmed the existence of bilateral deficit in RT. Vandervoort et al. (25) studied the bilateral deficit in the bench press in three different situations involving isometric and isotonic contractions at low and high speeds using the isokinetic machine. The bilateral performance was lower than the unilateral at high speed. However, at low speeds, as well as in isometric work, the differences were not significant. This indicates that the speed of movement and different angles can also have influence on the bilateral deficit.

Chaves et al. (8) showed through the 1 RM test in elbow flexion and leg extension that the sum of unilateral forces is significantly greater than the bilateral force. However, no significant difference for leg flexion was verified. Simao et al. (22) evaluated 24 untrained subjects of both genders and the authors found that bilateral deficit occurred for 1 RM, but no significant differences were found for muscle power in elbow flexion. Contrary to our results, the study of Monteiro and Simao (14) submitted 20 women (age, 18-30 yrs) to a 10 RM test in knee extension and elbow flexion movement. They showed that the bilateral workload was greater than the unilateral sum in both exercises.

The mechanisms involved in muscle contraction are complex and involve basically the interaction between the sensory receptors, the central command of nervous system and skeletal muscles, in which, through negative feedback, the final product is the sliding of the contractile proteins actin and myosin (11). The right cerebral hemisphere commands the muscular contractions of the left side of the body and vice-versa. The literature references the bilateral deficit phenomenon as a consequence of several physiological aspects.

During the bilateral contraction there is higher motor complexity and simultaneous activation of both cerebral hemispheres. Thus, it seems that in this situation there is less activation of each hemisphere, which causes a significant reduction in the activation of motor units, allowing for lower force production. Whereas, during the unilateral contraction, where only one cerebral hemisphere is acting, there seems to be greater neural activation and increased recruitment of motor units, mainly type II fibers, which cause increased production of muscle strength (9). This inter-hemispheric inhibition may be a limiting factor of motor performance which would explain the results of this study.

It is important to note the limitations of this study. The sample was composed of only males, which limits the interpretation of the findings. Another limitation is that only one attempt for each contraction (dominant, non-dominant and bilateral) was performed. It is possible that if more attempts were made the subjects may have achieved higher levels of strength.

The load of training is one of the main variables that must be taken into consideration during the RT prescription. According to the results of this study, the sum of unilateral isometric contractions of knee extension is greater than the bilateral contraction. This would make the unilateral training an effective strategy for mobilizing higher loads during the RT, which would entail an important stimulus for the development of strength and muscle hypertrophy.

CONCLUSIONS

The results of this study confirmed our hypothesis that bilateral deficit occurs at 120[degrees] of maximum isometric knee extension in trained men. However, future studies should investigate other angles, other exercises, and the inclusion of untrained subjects and women to compare the results and to present further information about the bilateral deficit during the RT.

ACKNOWLEDGMENTS

The authors acknowledge Caroline Teixeira for her help in the development of this manuscript.

REFERENCES

(1.) Alves HB, Simao R, Dias MR. Repetitions number and percentage of maximum load: Comparison between single and multiple joint exercises. Rev Bras Prescr Fisiol Exerc. 2012; 6:157-163.

(2.) American College of Sports Medicine. Position stand on quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med Sci Sports Exerc. 2011; 43:1334-1359.

(3.) American College of Sports Medicine. Position stand on progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009; 41:687-708.

(4.) American College of Sports Medicine, American Heart Association. Joint position stand: Exercise and acute cardiovascular events: placing the risks into perspective. Med Sci Sports Exerc. 2007; 39:886-897.

(5.) Bottaro M, Veloso J, Salles BF, Simao R, Celes R, Brown LE. Early phase adaptations of single vs. multiple sets os strength training on upper and lower body strength gains. Isokinet Exerc Sci. 2009; 17:207-212.

(6.) Burt J, Wilson R, Willardson JM. A comparison of once versus twice per week training on leg press strength in women. J Sports Med Phys Fitness. 2007; 47:13-17.

(7.) Campos GER, Luecke TJ, Wendeln HK, Toma K, Hagerman FC, Murray TF, Ragg KE, Ratamess NA, Kraemer WJ, Staron RS. Muscular adaptations in response to three different resistance-training regimens: Specificity of repetition maximum training zones. Eur J Appl Physiol. 2002; 88:50-60.

(8.) Chaves CPG, Guerra CPC, Moura SRG, Nicoli AIV, Felix I, Simao R. Deficit bilateral nos movimentos de flexao e extensao de perna e flexao de cotovelo. Rev Bras Med Esporte. 2004; 10:505-508.

(9.) Dieen JHV, Ogita F, Haan A. Reduce neural drive in bilateral exertions: A performance-limiting factor? Med Sci Sports Exerc. 2003; 35:111-118.

(10.) Gullet JC, Tillman MD, Gutierrez GM, Chow JW. A biomechanical comparison of back and front squats in healthy trained individuals. J Strength Cond Res. 2009; 23:284-292.

(11.) Guyton AC, Hall JE. Textbook of Medical Physiology. 12th Edition. Philadelphia, PA: Saunders, 2011.

(12.) Jakobi JM, Cafarelli E. Neuromuscular drive and force production are not altered during bilateral contractions. J Appl Physiol. 1998; 84:200-206.

(13.) Khodiguian N, Cornwell A, Lares E, Dicaprio PA, Hawkins SA. Expression of the bilateral deficit during reflexively evoked contractions. J Appl Physiol. 2003; 94:171-178.

(14.) Monteiro WD, Simao R. Is there bilateral deficit in the practice of 10RM in arm and leg exercises? Rev Bras Med Esporte. 2006; 12:115-118.

(15.) Newton RU, Spreuwenberg LPB, Hakkinen K. Relationship between the number of repetitions and selected percentages of one repetition maximum in free weight exercises in trained and untrained men. J Strength Cond Res. 2006; 20:819-823.

(16.) Patten C, Kamen G. Adaptations in motor unit discharge activity with force control training in young and older human adults. Eur J Appl Physiol. 2000; 83:128-143.

(17.) Pinto RS, Botton CE, Kuckartz BT, Lima CS, Moraes AC, Bottaro M. Evaluation of bilateral deficit in isometric contractions of the knee extensors. Rev Bras Cineantropom Desempenho Hum. 2012; 14:202-211.

(18.) Reis LGR, Teixeira ALS, Paiva DB, Santos SM, Moraes E, Simao R, Dias MR. Acute vascular responses in different body positions in resistance training. Rev Bras Prescr Fisiol Exerc. 2012; 6:192-200.

(19.) Salles BF, Simao R, Miranda F, Novaes JS, Lemos A, Willardson JM. Rest interval between sets in strength training. Sports Med. 2009; 39:765-777.

(20.) Shephard RJ. PAR-Q, Canadian home fitness test and exercise screening alternatives. Sports Med. 1988; 5:185-195.

(21.) Shimano T, Kraemer WJ, Spiering BA, Volek JS, Hatfield DL, Silvestre R, Vingren JL, Fragala MS, Maresh CM, Fleck SJ, Newton RU, Spreuwenberg LPB, Hakkinen K. Relationship between the number of repetitions and selected percentages of one repetition maximum in free weight exercises in trained and untrained men. J Strength Cond Res. 2006; 20:819-823.

(22.) Simao R, Monteiro WD, Araujo CGS. Maximal muscle power in unilateral and bilateral elbow flexion. Rev Bras Med Esporte. 2001; 7:157-162.

(23.) Simao R, Salles BF, Figueiredo T, Dias I, Willardson JM. Exercise order in resistance training. Sports Med. 2012; 42:251-265.

(24.) Simao R, Spineti J, Salles BF, Matta T, Fernandes L, Fleck SJ, Rhea MR, Strom-Olsen HE. Comparison between nonlinear and linear periodized resistance training: Hypertrophic and strength effects. J Strength Cond Res. 2012; 26:1389-1395.

(25.) Vandervoort AA, Sale DG, Moroz JR. Strength velocity relation and fatigability of unilateral versus bilateral arm extension. Eur J Appl Physiol Occup Physol. 1987; 56:201-205.

Andre Luiz S. Teixeira, Julio Cezar A. Narciso, Ibrahim Taroco Salomao, Marcelo Ricardo C. Dias

Granbery Methodist Institute, Laboratory of Exercise Physiology, Juiz de Fora, MG, Brazil

Address for correspondence: Marcelo Ricardo C. Dias, Laboratory of Exercise Physiology, Granbery Methodist Institute, Juiz de Fora, MG, Brazil, 36010-532. Phone: 55 (32) 2101-1838; Email: diasmr@gmail.com

Table 1. Descriptive Data of the Subjects (n=27).
Variables
                         Mean [+ or -] SD

Age (yrs)                25.1 [+ or -] 8.6
Weight (kg)              74.9 [+ or -] 10.9
Height (cm)             178.1 [+ or -] 5.2
BMI (kg x [m.sup.-2])    23.5 [+ or -] 2.8

Table 2. Data of Strength of the Dominant and Non-Dominant Legs
(mean [+ or -] SD).

                    Dominant            Non-dominant       P-value

Strength (N)   357.7 [+ or -] 52.4   360.7 [+ or -] 57.8    0.600
COPYRIGHT 2013 American Society of Exercise Physiologists
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2013 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Teixeira, Andre Luiz S.; Narciso, Julio Cezar A.; Salomao, Ibrahim Taroco; Dias, Marcelo Ricardo C.
Publication:Journal of Exercise Physiology Online
Article Type:Author abstract
Date:Feb 1, 2013
Words:2440
Previous Article:Is the HRmax=220-age equation valid to prescribe exercise training in children?
Next Article:Effects of a resistance exercise session on the physiological response and time to exhaustion during submaximal and maximal cycling.
Topics:

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters