The Bilateral Deficit Phenomenon in Elbow Flexion: Explanations for Its Inconsistent Occurrence and Detection

The underlying mechanism(s) of the Bilateral Deficit (BLD) phenomenon is without consensus. Methodological inconsistencies across prior works may be an important source of equivocal results and interpretations. Based on repeatability problems with the BLD measure and maximal force definition, the presence or absence of the BLD phenomenon is altered, shifting conclusions of its mechanistic cause. Our purpose in this study was to examine methodological inconsistencies in applying the BLD measure to establish optimal methods for evaluating the underlying mechanism. Eleven healthy participants engaged in one familiarity and five test sessions, completing bilateral and unilateral elbow maximal voluntary isometric contractions. We defined maximal force by averaged and absolute peak and plateau values. BLD was evident if the bilateral index (BI), the ratio of the bilateral over summed unilateral forces, was statistically different from zero. We addressed interclass correlations (ICC), Chronbach’s α, standard error of the mean, and minimal detectable change between and within sessions for all force measures and BI. We evaluated all combinations of sessions (i.e., 1–2, 3–5, 5–6) and maximal forces to establish the optimal number of sessions to achieve reliability. BLD was present for test sessions, but not for familiarization. All measures of maximal force were highly reliable between and within sessions (ICC(2,1) ≥ .895). BI was only considered significantly reliable in sessions 3–5 ( p < .027), defined by absolute and average plateau forces, but reliability was still quantifiably poor (absolute: ICC(2,1) = .392; average: ICC(2,1) = .375). These results demonstrate that high force reliability within and between sessions does not translate to stable and reliable BI, potentially exposing the lack of any defined BLD mechanism.

Bilateral Deficits during Maximal Grip Force Production in Late Postmenopausal Women

The purpose of this study was to investigate bilateral deficit patterns during maximal hand-grip force production in late postmenopausal women. Twenty late postmenopausal and 20 young premenopausal women performed maximal isometric grip force production tasks with dominant and nondominant hands and both hands, respectively. For late postmenopausal women, pulse wave analysis was used for identifying a potential relationship between maximal hand-grip strength and risk factors of cardiovascular disease. The findings showed that late postmenopausal women produced significantly decreased maximal hand-grip strength in dominant and nondominant and bilateral hand conditions compared to those of premenopausal women. Bilateral deficit patterns appeared in late postmenopausal women. For late postmenopausal women, decreased dominant and bilateral hand-grip forces were significantly related to greater bilateral deficit patterns. Further, less maximal hand-grip strength in unilateral and bilateral hand conditions correlated with greater central pulse pressure. These findings suggested that age-related impairments in muscle strength and estrogen deficiency may interfere with conducting successful activities of bilateral movements. Further, assessing maximal dominant hand-grip strength may predict bilateral deficit patterns and risk of cardiovascular disease in late postmenopausal women.

Relación de la Asimetría Bilateral y el Déficit Bilateral con la Velocidad del Cambio de Dirección en Atletas Cadetes de Karate: Un estudio Piloto (Relationship of Bilateral Asymmetry and Bilateral Deficit with the Change of Direction Speed in Cadet Kara

Antecedentes: La Asimetría Bilateral (AB) y el Déficit Bilateral (DBL) y su potencial relación negativa con el rendimiento físico es actualmente estudiada, aunque la relación con la velocidad del cambio de dirección (CODS) y el sprint lineal (5-M) en atletas de karate se desconoce. Objetivo: Examinar las correlaciones entre la AB y el DBL con el CODS y 5-M, así como entre el salto horizontal con el CODS y 5-M. Métodos: Diez atletas hombres de categoría cadetes participaron voluntariamente de este estudio. Entre las habilidades físicas evaluadas se incluyeron: salto horizontal bilateral (SBJ), salto horizontal unilateral derecho (RSBJ), salto horizontal unilateral izquierdo (LSBJ), CODS y 5-M. Posteriormente, la AB y el DBL fueron calculados. Resultados: Se reportó una baja AB (5.17 ± 3.61%) y presencia de DBL (-36.9 ± 6.2 %). Correlaciones moderadas entre la AB con CODS (r = -.38; R2 = .15%; p = .30) y 5-M (r = -.47; R2 = .22%; p = .19) y entre DBL con 5-M (r = .51; R2 = .26%; p = .16) y bajas con CODS (r = .20; R2 = .04%; p = .60). Correlaciones significativas (p < .05) entre CODS con RSBJ (r = -.92; R2 = .85%; p = .00), SBJ (r = -.87; R2 = .75%; p = .00) y LSBJ (r = -.82; R2 = .67%; p = .00). Conclusiones: La AB y el DBL se relacionarían negativamente con el CODS y 5-M. Aunque, el CODS se relaciona con la fuerza explosiva horizontal bilateral y unilateral. Abstract. Background: Bilateral asymmetry (AB) and Bilateral Deficit (DBL) and their potential negative relationship with physical performance is currently studied, although the relationship with change of direction speed (CODS) and linear sprint (5-M) in karate athletes is unknown. Aim: To examine correlations between AB and DBL with CODS and 5-M, as well as between horizontal jump with CODS and 5-M. Methods: Ten male cadet athletes voluntarily participated in this study. The physical abilities assessed included: bilateral horizontal jump (SBJ), right unilateral horizontal jump (RSBJ), left unilateral horizontal jump (LSBJ), CODS and 5-M. Subsequently, AB and DBL were calculated. Results: Low AB (5.17 ± 3.61%) and presence of DBL (-36.9 ± 6.2 %) were reported. Moderate correlations between AB with CODS (r = -.38; R2 = .15%; p = .30) and 5-M (r = -.47; R2 = .22%; p = .19) and between DBL with 5-M (r = .51; R2 = .26%; p = .16) and low with CODS (r = .20; R2 = .04%; p = .60). Significant correlations (p < .05) between CODS with RSBJ (r = -.92; R2 = .85%; p = .00), SBJ (r = -.87; R2 = .75%; p = .00) and LSBJ (r = -.82; R2 = .67%; p = .00). Conclusions: AB and DBL would be negatively related to CODS and 5-M. However, CODS is related to bilateral and unilateral horizontal explosive strength.

Performance fatigability and the bilateral deficit during maximal, isokinetic leg extensions in men and women

BACKGROUND: Few studies have examined sex differences in performance fatigability and the bilateral deficit in a dynamic modality. OBJECTIVES: The purpose of this study was to examine: 1) Leg-, mode-, and sex-specific differences in performance fatigability during maximal, dynamic leg extension muscle actions and; 2) the time course of fatigue-induced changes in the bilateral deficit for both men and women. METHODS: Eleven men and 11 women participated in 3 test visits consisting of 50 maximal, concentric, isokinetic leg extensions at 60∘/s. Each visit was randomized to perform either unilateral right leg only (RL), unilateral left leg only (LL), or bilateral (BL) leg extensions. RESULTS: The BL performance fatigability was significantly (p< 0.001) less than RL and LL. Both men and women demonstrated significant (p< 0.001) declines in moment and an attenuation of the bilateral deficit throughout the fatiguing task. There were no differences between sex for performance fatigability (p= 0.128) or the bilateral deficit (p= 0.102). CONCLUSIONS: Unilateral muscle actions were more susceptible to fatigue than BL muscle actions. Men exhibited an earlier decline in moment than women, however, men and women exhibited similar magnitudes and patterns of decline in the bilateral deficit.

Bilateral deficit: relationships with training history and functional performance

The purpose of the study was to investigate the magnitude of bilateral deficit (BLD) in trained males and examine its relationship with functional performance and recent resistance training history. Ten physically active males (age: 23.02±1.27 years) self-reported the number of unilateral and bilateral exercises within their structured resistance training schedule. During two visits to the laboratory, participants performed unilateral and bilateral squat jumps (SJ) and isometric leg extensions (ILE) for the quantification of BLD. Participants also performed bilateral countermovement jumps (CMJ) and a change of direction (COD) test to quantify functional performance. The performance outcomes and information regarding training history were then correlated with the bilateral index (BLI) metric. The key findings were that: (a) a lower BLD in SJ peak power related to a greater CMJ peak force (r=.728; p=.02) and peak power (r=.750; p=.01), (b) the BLI in the ILE was unrelated to performance outcomes, and (c) BLI was unrelated to the mean number of bilateral and unilateral exercises in the structured resistance training programme of participants. In conclusion, lower levels of BLD may be advantageous for bilateral tests of functional performance (i.e. jumps) however there is a need to consider the mechanical similarity between the performance and BLD measure. Finally, the balance of unilateral and bilateral exercises in an individual’s recent resistance training history is not sensitive to the BLI measured during dynamic or isometric assessments.