Significant Bilateral Deficits Research Articles

Variability of unilateral and bilateral isometric muscle strength of lower extremities extensors in young females and males.

The muscle strength of the lower extremity extensors can be evaluated in the closed kinetic chain (CKC) during unilateral or bilateral conditions. Factors such as the mass and length of the muscle, joint angle, type of contraction, and gender influence the magnitude of the muscle strength. The aim of this study was to compare the isometric strength of lower extremity extensors between the different knee extension angles (KEs) as well as between bilateral and unilateral conditions. Nineteen female students (age: 20.2 ± 0.6 years) and nineteen male students (age: 20.3 ± 0.7 years) participated in the study. The muscle strength was evaluated in CKC using the strain gauge dynamometer. The analysis included values of the maximum muscle strength normalized to body mass (MS/BM) for the six KEs of 80°, 70°, 60°, 50°, 40° and 30°. A significant main effect in the MS/BM values for the angle factor (p < 0.001) and condition factor (p < 0.001) was found. Moreover, there was a non-significant interaction effect between the angle factor and gender factor (p = 0.476) as well as between the condition factor and gender factor (p = 0.770). Comparisons showed significant differences in the MS/BM values between the six KEs (p < 0.001). Furthermore, significantly lower MS/BM values for bilateral conditions than unilateral conditions at the 30° KE were observed (p < 0.001). The decrease in KE by 10° significantly increased the muscle strength of the lower extremity extensors. Gender did not affect the change in MS/BM values with the change in KE and conditions. Findings also revealed significant bilateral deficit, i.e., significantly a lower summed muscle strength during bilateral conditions than unilateral conditions. The study emphasized the importance of selecting the 30° KE as the optimal angle to assess the maximum strength developed in CKC.

Unilateral and Bilateral Isokinetic Leg Extensions Exhibit No Differences in Neuromuscular Excitation Under Maximal and Fatiguing Conditions.

Abstract Anders, JPV, Neltner, TJ, Smith, RW, Arnett, JE, Housh, TJ, Schmidt, RJ, and Johnson, GO. Unilateral and bilateral isokinetic leg extensions exhibit no differences in neuromuscular activation under maximal and fatiguing conditions. J Strength Cond Res 38(3): 474–480, 2024—The bilateral deficit is a phenomenon where force production during a bilateral (BL) muscle action is less than the sum of force produced when the muscle action is performed unilaterally (UL) with both limbs. The purpose of this study was to compare peak force, electromyographic (EMG) amplitude (AMP), and mean power frequency (MPF) of the nondominant leg between UL and BL isokinetic leg extensions. Eleven recreationally trained men (mean ± SD; age = 20.8 ± 1.7 years; body mass = 84.0 ± 16.2 kg; height = 179.3 ± 7.2 cm) volunteered to participate in this study. The 2 test visits included UL and BL maximal isokinetic leg extensions at 180°·second−1 followed by a fatiguing task of either 50 UL or 25 UL followed immediately by 25 BL (ULBL) maximal, isokinetic leg extensions at 180°·second−1, in random order on separate days. The results demonstrated a significant (p = 0.015, = 0.460) bilateral deficit in force (UL = 56.29 ± 11.20 kg; BL = 50.32 ± 7.35 kg; d = 0.63; 95% CI [1.42, 10.52]) but no significant bilateral deficit in EMG AMP (p = 0.892, = 0.002). The peak force during the fatiguing task demonstrated a significant main effect for repetition (p &lt; 0.001, = 0.943) characterized by a reduced peak force from repetitions 20–50. Similarly, EMG MPF demonstrated a significant main effect for repetition (p &lt; 0.001, = 0.702) characterized by a reduced EMG MPF from repetitions 35–50. There were no significant effects (p = 0.102–0.387, = 0.096–0.203) for EMG AMP. These findings suggested that the bilateral deficit was not associated with a neuromuscular deficit and UL muscle actions may be used to potentiate force production of subsequent BL muscle actions.

Neuromuscular Adaptations to Unilateral vs. Bilateral Strength Training in Women.

Botton, CE, Radaelli, R, Wilhelm, EN, Rech, A, Brown, LE, and Pinto, RS. Neuromuscular adaptations to unilateral vs. bilateral strength training in women. J Strength Cond Res 30(7): 1924-1932, 2016-Considering the bilateral deficit, the sum of forces produced by each limb in a unilateral condition is generally greater than that produced by them in a bilateral condition. Therefore, it can be speculated that performing unilateral strength exercises may allow greater training workloads and subsequently greater neuromuscular adaptations when compared with bilateral training. Hence, the purpose of this study was to compare neuromuscular adaptations with unilateral vs. bilateral training in the knee extensor muscles. Forty-three recreationally active young women were allocated to a control, unilateral (UG) or bilateral (BG) training group, which performed 2 times strength training sessions a week for 12 weeks. Knee extension one repetition maximum (1RM), maximal isometric strength, muscle electrical activity, and muscle thickness were obtained before and after the study period. Muscle strength was measured in unilateral (right + left) and bilateral tests. Both UG and BG increased similarly their unilateral 1RM (33.3 ± 14.3% vs. 24.6 ± 11.9%, respectively), bilateral 1RM (20.3 ± 6.8% vs. 28.5 ± 12.3%, respectively), and isometric strength (14.7 ± 11.3% vs. 13.1 ± 12.5%, respectively). The UG demonstrated greater unilateral isometric strength increase than the BG (21.4 ± 10.5% vs. 10.3 ± 11.1%, respectively) and only the UG increased muscle electrical activity. Muscle thickness increased similarly for both training groups. Neither group exhibited pretesting 1RM bilateral deficit values, but at post-testing, UG showed a significant bilateral deficit (-6.5 ± 7.8%) whereas BG showed a significant bilateral facilitation (5.9 ± 9.0%). Thus, performing unilateral or bilateral exercises was not a decisive factor for improving morphological adaptations and bilateral muscle strength in untrained women. Unilateral training, however, potentiate unilateral specific strength gains.

Alterations in Quadriceps Voluntary Force Control Following Anterior Cruciate Ligament Injury

Although quadriceps strength is important following ACL injury, maximal activation of the quadriceps is rare during sporting situations and activities of daily living. Furthermore, functional stability of the knee joint depends on both adequate strength and the ability to produce force accurately. Previous studies assessing quadriceps force control following ACL injury have utilized constant sub-maximal isometric target forces. However, during most functional activities the quadriceps muscles are required to produce fluctuating force levels. Thus, the use of a testing protocol involving a cyclical or varying target force may better approximate quadriceps forces during functional activities. PURPOSE: To examine submaximal quadriceps force control in individuals with an ACL injury using a cyclical force target. METHODS: Eighteen (18) individuals (12M/6F; 29.8 ± 8.7years) within 8 months of unilateral isolated ACL injury (69.5 ± 42.5 days post-injury) and 18 healthy controls (12M/6F; 29.2 ± 6.8years) participated in the study. Participants performed an isometric quadriceps contraction to match an increasing force ramp from 5% to 25% body weight (BW), after which the ramp gradually reduced from 25% to 5% BW (0.10Hz). Four trials of 60s with 60s rest in between were performed. The root mean square error (RMSE) of quadriceps torque relative to target torque was determined, and compared between groups and limbs using a 2x2 ANOVA with repeated measures on limb. Sub-regional analysis assessed accuracy of force control over an increasing (ascending RMSE) and decreasing (descending RMSE) force ramp. RESULTS: There was significantly greater overall RMSE in both limbs of the ACL group compared to healthy controls (3.36 ± 1.8 %BW INV limb; 3.28 ± 1.2 %BW UNINV limb; 2.40 ± 0.61 %BW CONT; 2.40 ± 0.58 %BW UNINV CONT P=0.032). The ACL group had significantly higher descending RMSE in both limbs compared to healthy controls (3.92 ± 2.8 INV limb; 3.39 ± 1.6 UNINV limb; 2.43 ± 0.61 CONT; 2.36 ± 0.52 UNINV CONT P=0.035). Ascending RMSE did not differ between the ACL and control group limbs (P>0.05) CONCLUSIONS: There are significant bilateral deficits in submaximal quadriceps force control after ACL injury, compared to healthy controls, potentially contributing to altered knee function after ACL injury.

Sensorimotor Deficits Remain Despite Resolution of Symptoms Using Conservative Treatment in Patients With Tennis Elbow: A Randomized Controlled Trial

Bisset LM, Coppieters MW, Vicenzino B. Sensorimotor deficits remain despite resolution of symptoms using conservative treatment in patients with tennis elbow: a randomized controlled trial. Objectives To evaluate the time course of sensorimotor deficits in lateral epicondylalgia (LE; tennis elbow) and how these deficits may be influenced by common conservative treatments. Design Single-blind randomized controlled trial. Setting University laboratory, Australia. Participants A total of 198 participants with unilateral LE of a minimum 6 weeks duration and normative data from a group of 40 healthy participants. Interventions Participants with LE were randomly assigned to physical therapy, corticosteroid injection, or a wait-and-see approach with ergonomic advice. Main Outcome Measures Upper-limb reaction time (simple, 1-choice and 2-choice reaction time) and speed of movement were assessed at baseline and 6 and 52 weeks of follow-up. Results Patients with LE exhibited delayed reaction times ( P<.001) and slower movement speeds ( P<.001) for both the affected and unaffected arm at baseline, compared with normative data. Despite some improvement over time, significant bilateral deficits remained compared with healthy participants, with no significant differences between the affected and unaffected arm. Overall, there was no significant difference between the 3 treatment groups over time. Conclusions Sensorimotor deficits remain relatively unchanged over time and are present bilaterally in patients with unilateral LE. Treatment did not influence the time course of the sensorimotor deficits. This prompts conjecture as to the relationship and clinical relevance of sensorimotor deficits in LE. It should be noted that treatment evaluated in this study did not specifically target sensorimotor function, and further investigation into the significance of sensorimotor deficits in patients with LE is required.

Dynamic mapping of hippocampal development in childhood onset schizophrenia

Prior cross-sectional anatomic brain imaging studies of the hippocampus in schizophrenia have generally shown loss in total hippocampal volume although the progressive course of these changes remains unknown. We report the first prospective sub-regional maps of hippocampal development in childhood onset schizophrenia (COS), reconstructed from serial brain MRI scans of 29 children with COS scanned every 2 years (87 scans) and compared to 31 controls matched for age, sex, and scan interval (94 scans). As expected, the COS subjects showed significant bilateral deficits (9–10%) in total hippocampal volume which remained consistent between age 9 and 26. However sub-regional maps showed heterogeneous changes with loss of hippocampal volume in both anterior as well as posterior ends while the body of the hippocampus gained in volume suggesting that hippocampal subunits are differentially affected in schizophrenia.

Human bilateral deficit during a dynamic multi-joint leg press movement

Bilateral deficit has been used to describe the phenomenon of a reduction in performance during synchronous bilateral movements when compared to the sum of identical unilateral movements. The study of bilateral deficit in humans under isometric, and to a lesser extent, dynamic conditions has shown bilateral decreases in force and muscle activation, and delayed reaction time. Results are equivocal, however, and biomechanical analyses of dynamic conditions, i.e., movements, are lacking. Our purpose was to determine, through an analysis of kinematic, kinetic, and electromyographic (EMG) data, whether or not bilateral deficit was present during a dynamic multi-joint movement under conditions where the external load was relatively equal for unilateral and bilateral efforts. Five male participants performed repeated unilateral and bilateral maximal horizontal leg press jumps under 100% (1BW) and 200% (2BW) relative body weight loads. Significant bilateral deficits in resultant ground reaction impulse of 27.7% and 13.0% were present in 1BW and 2BW, respectively. Maximum joint power at the hip exhibited significant deficits in both 1BW and 2BW of 35.6% and 25.1%, respectively. In both 1BW and 2BW conditions, ankle (15.5% and 11.5%), knee (10.9% and 5.7%), and hip (38.5% and 30.4%) work was significantly affected. Statistically significant EMG bilateral deficits were found in every muscle in both conditions except for rectus femoris during the 2BW trials. Bilateral deficit values ranged from 9.1% to 20.9% for 1BW, while deficits between 6.1% and 20.7% were found in 2BW. These results indicate that during dynamic leg press, bilateral deficit does exist, but that individual muscle activation levels and joint kinetics are not equally affected.

Bilateral multifinger deficits in symmetric key-pressing tasks.

Maximal voluntary force during simultaneous bilateral and multifinger exertion has been shown to be smaller than the sum of unilateral or single-finger exertions. The goal of this study was to study the force deficit associated with bilateral multifinger tasks. Eight normal college students performed four types of maximal isometric key-pressing tasks: (1) unilateral single-finger, (2) bilateral single-finger, (3) unilateral multifinger, and (4) bilateral multifinger. Forces produced by the index (I), middle (M), ring (R), and little (L) fingers and surface electromyography (EMG) of extrinsic finger flexors were recorded. Multifinger deficit (MFD) was defined as the percentage difference between the force (or EMG) produced by a set of fingers and the sum of the forces (or EMGs) produced by the individual fingers in their unilateral single-finger tasks. Bilateral deficit (BLD) was defined as the percentage difference between the force (or EMG) produced by a set of fingers and the sum of the forces (or EMGs) produced by the finger subsets of the left and right hands. Significant BLD and MFD in force and EMG were found for all bilateral multifinger tasks and some of the bilateral single-finger tasks. Both BLD and MFD were dependent on the number of fingers involved. BLD ranged from 3% to 22.7% for force and from 8.9% to 31.0% for EMG, including bilateral single-finger and bilateral multifinger tasks. MFDs in force during bilateral I-, IM-, IMR-, and IMRL-finger tasks were 13.2%, 37.8%, 53.2%, 52.3%, respectively; and the corresponding MFDs in EMG were 11.7%, 51.3%, 67.6%, and 71.0%, respectively. BLD and MFD in EMG were found to vary in parallel with the corresponding force deficits. It was suggested that the neural ceiling effect remains the most plausible mechanism underlying the observed deficits. The central nervous system is unable to activate maximally a large number of muscle groups at the same time during tasks involving multiple body parts. During bilateral multifinger tasks, the ceiling effect may be organized hierarchically: (1) a certain limited neural drive is shared bilaterally, leading to a BLD; (2) at each hand, a certain limited neural drive is shared by multiple fingers, leading to MFD within a hand; (3) the deficits at bilateral and unilateral multifinger levels are cumulative during bilateral multifinger tasks, leading to a higher deficit associated with the tasks.

BILATERAL INDEX EXPRESSIONS AND IEMG ACTIVITY IN ELDERLY VS. YOUNG ADULTS

This study investigated the hypothesis that expressions of bilateral indices (BI) would be higher in elderly compared to young participants. To test this hypothesis, we had 20 older (73.3 ± 4.4) and 21 younger (23.0 ± 0.7) participants perform maximal voluntary isometric contractions (MVC) of the elbow flexor muscles, using the right arm only (RU), left arm only (LU) and both arms simultaneously (R & L BL). These actions were repeated at perceived intensities of 25%, 50%, & 75% MVC. Force data and integrated electromyographical (EMG) activity of the biceps and triceps muscles were collected during each trial. Bilateral index values were calculated [(RBL+LBL)/(RU+LU) × 100–100] for each intensity level in both groups using absolute forces (ABI) and forces normalized to their respective mode (unilateral or bilateral) maximums (MBI). The ABI was parsed into a perceptual component, defined as the MBI, and a physiological component, defined as ABI-MBI. Significant bilateral deficits (p < 0.05), defined as ABI < 0, existed at maximal and submaximal intensities but the submaximal deficits (14–18%) were larger than the maximal deficits (11%). The physiological component of the ABI was 11% at all intensity levels for both groups. There was an inverse relationship between the perceptual component of the ABI and the level of effort. Normalized integrated EMG values were significantly higher (p < 0.05) for unilateral trials than for bilateral trials at all intensity levels. There were no significant differences between the elderly and young participants. Despite the decrease in fast twitch motor units associated with aging, bilateral deficits exist in older adults, are similar to those observed for younger adults, and remain larger for submaximal intensities.

Functional magnetic resonance imaging evidence for disrupted basal ganglia function in schizophrenia.

This study was an examination of basal ganglia dysfunction in schizophrenia using functional magnetic resonance imaging (fMRI). The authors used a motor sequencing task to investigate activation of the caudate, anterior putamen plus globus pallidus, and posterior putamen plus globus pallidus in eight subjects with schizophrenia and 12 group-matched comparison subjects. Differences in activation of the thalamus, the target of direct output from the globus pallidus, were also examined. The schizophrenia subjects showed significant bilateral deficits in the posterior putamen, globus pallidus, and thalamus but not the anterior putamen plus globus pallidus or caudate. Functional connectivity analysis revealed that the deficits in thalamic activation were related to deficits in posterior putamen and globus pallidus activation. These results provide fMRI evidence for basal ganglia dysfunction in subjects with schizophrenia and suggest that this deficit results in disrupted outflow to the thalamus. These deficits may underlie the behavioral impairments in goal-directed action observed in schizophrenia.