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ABSTRACT: Ortega, DG, Housh, TJ, Smith, RW, Arnett, JE, Neltner, TJ, Schmidt, RJ, and Johnson, GO. The effects of anchoring a fatiguing forearm flexion task to a high versus low rating of perceived exertion on torque and neuromuscular responses. J Strength Cond Res 38(5): e219-e225, 2024-This study examined the torque and neuromuscular responses following sustained, isometric, forearm flexion tasks anchored to 2 ratings of perceived exertion (RPE). Nine men (mean ± SD: age = 21.0 ± 2.4 years; height = 179.5 ± 5.1 cm; body mass = 79.6 ± 11.4 kg) completed maximal voluntary isometric contractions (MVIC) before and after sustained, isometric, forearm flexion tasks to failure anchored to RPE = 2 and RPE = 8. The amplitude (AMP) and mean power frequency (MPF) of the electromyographic (EMG) signal were recorded from the biceps brachii. Normalized torque was divided by normalized EMG AMP to calculate neuromuscular efficiency (NME). A dependent t-test was used to assess the mean difference for time to task failure (TTF). Repeated-measures analysis of variances was used to compare mean differences for MVIC and normalized neuromuscular parameters. There was no significant difference in TTF between RPE = 2 and RPE = 8 (p = 0.713). The MVIC decreased from pretest to posttest at RPE = 2 (p = 0.009) and RPE = 8 (p = 0.003), and posttest MVIC at RPE = 8 was less than that at RPE = 2 (p < 0.001). In addition, NME decreased from pretest to posttest (p = 0.008). There was no change in normalized EMG AMP or EMG MPF (p > 0.05). The current findings indicated that torque responses were intensity specific, but TTF and neuromuscular responses were not. Furthermore, normalized EMG AMP and EMG MPF remained unchanged but NME decreased, likely due to peripheral fatigue and excitation-contraction coupling failure. Thus, this study provides information regarding the neuromuscular responses and mechanisms of fatigue associated with tasks anchored to RPE, which adds to the foundational understanding of the relationship between resistance exercise and the perception of fatigue.
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Electromiografía , Antebrazo , Contracción Isométrica , Fatiga Muscular , Músculo Esquelético , Esfuerzo Físico , Torque , Humanos , Masculino , Adulto Joven , Antebrazo/fisiología , Contracción Isométrica/fisiología , Esfuerzo Físico/fisiología , Fatiga Muscular/fisiología , Músculo Esquelético/fisiología , Percepción/fisiología , AdultoRESUMEN
BACKGROUND: Ratings of perceived exertion (RPE) can be used to regulate exercise intensity. This study examined the effect of anchor scheme on performance fatigability and neuromuscular responses following fatiguing forearm flexion tasks. METHODS: Twelve men (age 20.9±2.2 years; height 179.8±5.3 cm; body mass 80.2±9.9 kg) performed sustained, isometric forearm flexion tasks to failure anchored to RPE=6 (RPEFT) and the torque (TRQFT) that corresponded to RPE=6. Pre-test and post-test maximal voluntary isometric contractions (MVIC) were performed to quantify changes in the amplitude (AMP) and mean power frequency (MPF) of the electromyographic (EMG) and mechanomyographic (MMG) signals. Neuromuscular efficiency (NME) was calculated by dividing normalized torque by normalized EMG AMP. A dependent t-test was used to assess the mean difference for time to task failure (TTF). Repeated measures ANOVAs were used to compare mean differences for performance fatigability and normalized neuromuscular parameters. RESULTS: The RPEFT had a greater TTF than the TRQFT (P<0.001). MVIC and NME decreased from pre-test to post-test following the RPEFT and TRQFT (P<0.05) with no differences between anchor schemes. Following the TRQFT, normalized EMG MPF decreased from pre-test to post-test (P=0.004). Following the RPEFT, normalized MMG MPF increased from pre-test to post-test (P=0.021). There were no changes in normalized EMG AMP or MMG AMP (P>0.05). CONCLUSIONS: These findings indicated anchor scheme-specific neuromuscular responses and TTF, despite no difference in performance fatigability. Furthermore, performance fatigability was likely due to peripheral fatigue (based on normalized EMG MPF and NME) following the TRQFT, but peripheral and central fatigue (based on normalized MMG MPF and NME) following the RPEFT.
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Electromiografía , Contracción Isométrica , Fatiga Muscular , Esfuerzo Físico , Humanos , Masculino , Fatiga Muscular/fisiología , Contracción Isométrica/fisiología , Adulto Joven , Esfuerzo Físico/fisiología , Torque , Antebrazo/fisiología , Percepción/fisiología , Adulto , Músculo Esquelético/fisiologíaRESUMEN
PURPOSE: The present study examined the effects of sustained, isometric low- versus high-intensity tasks on time to task failure (TTF), performance fatigability (PF), ratings of perceived exertion (RPE), and the perceived causes of task termination from a post-test questionnaire (PTQ). METHODS: Ten men (mean ± SD: age = 21.1 ± 2.3 years; height = 180.2 ± 5.7 cm; body mass = 79.5 ± 8.8 kg) performed maximal voluntary isometric contractions (MVICs) before and after fatiguing, isometric forearm flexion tasks anchored to the torque corresponding to RPE values of 2 (TRQ2FT = 23.8 ± 7.1 N·m) and 8 (TRQ8FT = 60.9 ± 11.4 N·m). In addition, the subjects completed a PTQ which surveyed whether the perceived sensations of fatigue or pain, and/or the psychological factors of loss of focus and motivation contributed to the decision to terminate the task. Repeated measures ANOVAs, Wilcoxon-Signed Rank tests, and Spearman's Rank-Order Correlations were used to analyze the data. RESULTS: Across the fatiguing tasks, there were similar decreases in MVIC torque (95.2 ± 20.3 vs. 68.9 ± 15.6 N·m; p < 0.001) and RPE values (p = 0.122) at task failure for TRQ2FT (7.4 ± 2.7) and TRQ8FT (8.9 ± 1.0), but a longer (p = 0.005) TTF for the TRQ2FT (245.0 ± 177.0 s) than TRQ8FT (36.8 ± 11.1 s). CONCLUSIONS: Despite reaching task failure, the subjects were able to perform MVICs that were 100-300% greater than the target torque values within seconds of terminating the tasks. Thus, we hypothesized that task failure was not caused by an inability to produce sufficient torque to sustain the tasks, but rather an unwillingness to continue the task.
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Contracción Isométrica , Fatiga Muscular , Esfuerzo Físico , Humanos , Masculino , Fatiga Muscular/fisiología , Contracción Isométrica/fisiología , Adulto Joven , Esfuerzo Físico/fisiología , Músculo Esquelético/fisiología , Percepción/fisiología , Adulto , TorqueAsunto(s)
Pierna , Fatiga Muscular , Humanos , Músculo Esquelético , Contracción Muscular , ElectromiografíaRESUMEN
ABSTRACT: Ortega, DG, Housh, TJ, Smith, RW, Arnett, JE, Neltner, TJ, Anders, JPV, Schmidt, RJ, and Johnson, GO. The effects of a sustained, isometric forearm flexion task to failure on torque and neuromuscular responses at 3 elbow joint angles. J Strength Cond Res 38(1): e25-e33, 2024-This study examined the effects of a sustained, isometric forearm flexion task anchored to torque to task failure on maximal voluntary isometric contraction (MVIC) and neuromuscular responses at 3 elbow joint angles. Eleven women (mean ± SD: age = 20.8 ± 2.7 years, height = 169.3 ± 7.4 cm, body mass = 67.7 ± 6.9 kg) performed two 3s forearm flexion MVICs at elbow joint angles (JAs) of 75°, 100°, and 125° before and after a sustained, isometric forearm flexion task to failure at a fatiguing joint angle of 100° anchored to a torque value that corresponded to a rating of perceived exertion of 8 (RPE = 8). The amplitude (AMP) and mean power frequency (MPF) of the electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the biceps brachii. Repeated-measures ANOVAs were used to compare mean differences for MVIC and neuromuscular parameters. Collapsed across JAs, MVIC (p < 0.001) and EMG MPF (p = 0.006) pretest values were greater than posttest values. Collapsed across time, EMG MPF at JA75 was greater than JA100 (p < 0.001) and JA125 (p < 0.001), and JA100 was greater (p = 0.007) than JA125. For EMG AMP, there was a fatigue-induced decrease at JA75 (p = 0.003). For neuromuscular efficiency (NME = normalized torque/normalized EMG AMP), there were decreases from pretest to posttest at JA100 (p = 0.002) and JA125 (p = 0.008). There were no significant interactions or main effects for MMG AMP and MMG MPF. From these findings, it was hypothesized that the decline in MVICs at JA75, JA100, and JA125 was due to fatigue-induced metabolic perturbations that resulted in JA-specific neuromuscular responses. Thus, neuromuscular parameters may provide insight into the JA-specific mechanisms of fatigue.
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Articulación del Codo , Humanos , Femenino , Adolescente , Adulto Joven , Adulto , Antebrazo , Torque , Músculo Esquelético/fisiología , Contracción Isométrica/fisiología , Electromiografía/métodosRESUMEN
BACKGROUND: Recently, tracheal narrowing has been recognized as a significant comorbid condition in patients with Morquio A, also known as mucopolysaccharidosis IVA. We studied a large cohort of patients with Morquio A to describe the extent of their tracheal narrowing and its relationship to airway management during anesthesia care. METHODS: This is an observational study, collecting data retrospectively, of a cohort of patients with Morquio A. Ninety-two patients with Morquio A syndrome were enrolled, among whom 44 patients had their airway evaluated by computed tomography angiography and had undergone an anesthetic within a year of the evaluation. Our hypothesis was that the tracheal narrowing as evaluated by computed tomography angiography increases with age in patients with Morquio A. The primary aim of the study was to examine the degree of tracheal narrowing in patients with Morquio A and describe the difficulties encountered during airway management, thus increasing awareness of both the tracheal narrowing and airway management difficulties in this patient population. In addition, the degree of tracheal narrowing was evaluated for its association with age or spirometry parameters using Spearman's rank correlation. Analysis of variance followed by the Bonferroni test was used to further examine the age-based differences in tracheal narrowing for the 3 age groups: 1 to 10 years, 11 to 20 years, and >21 years. RESULTS: Patient age showed a positive correlation with tracheal narrowing ( rs= 0.415; 95% confidence interval [95% CI], 0.138-0.691; P = .005) with older patients having greater narrowing of the trachea. Among spirometry parameters, FEF25%-75% showed an inverse correlation with tracheal narrowing as follows: FEF25%-75% versus tracheal narrowing: ( rs = -0.467; 95% CI, -0.877 to -0.057; P = .007). During anesthetic care, significant airway management difficulties were encountered, including cancelation of surgical procedures, awake intubation using flexible bronchoscope, and failed video laryngoscopy attempts. CONCLUSIONS: Clinically significant tracheal narrowing was present in patients with Morquio A, and the degree of such narrowing likely contributed to the difficulty with airway management during their anesthetic care. Tracheal narrowing worsens with age, but the progression appears to slow down after 20 years of age. In addition to tracheal narrowing, spirometry values of FEF25%-75% may be helpful in the overall evaluation of the airway in patients with Morquio A.
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Anestesia , Anestésicos , Mucopolisacaridosis IV , Humanos , Lactante , Preescolar , Niño , Adulto Joven , Adulto , Adolescente , Mucopolisacaridosis IV/cirugía , Estudios Retrospectivos , Anestesia/métodos , Intubación Intratraqueal/efectos adversos , Intubación Intratraqueal/métodos , Laringoscopía/métodosRESUMEN
OBJECTIVES: To examine the effects of joint angle (JA) on maximal voluntary isometric contractions (MVIC) and neuromuscular responses following a sustained, isometric forearm flexion task anchored to a rating of perceived exertion (RPE) of 8 (RPE=8). METHODS: Nine women (age: 20.7±2.9 yrs; height: 168.8±7.2 cm; body mass: 66.3±6.8 kg) performed 2,3s forearm flexion MVICs at JAs of 75°, 100°, and 125° prior to and following a sustained, isometric forearm flexion task anchored to RPE=8 to task failure (torque reduced to zero) at JA100. Electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the biceps brachii. RESULTS: The MVIC at JA100 (collapsed across Time) was significantly greater (p<0.05) than JA75 and JA125. The pre-test MVIC was significantly greater (p<0.001) than the post-test. For EMG amplitude (AMP) and EMG mean power frequency (MPF), pre-test values were significantly greater (p<0.05) than the post-test values, with no differences between JAs. For MMG AMP and MMG MPF, there were no significant (p>0.05) differences between Time or JAs. Pre-test neuromuscular efficiency (normalized MVIC/normalized EMG AMP) was significantly greater (p=0.005) than post-test. CONCLUSION: Following a sustained, isometric forearm flexion task anchored to RPE=8 at JA100, the fatigue-induced MVIC and neuromuscular responses were not affected by JA.
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Antebrazo , Extremidad Superior , Femenino , Humanos , Adolescente , Adulto Joven , Adulto , Contracción Isométrica , TorqueRESUMEN
ABSTRACT: Neltner, TJ, Sahoo, PK, Smith, RW, Anders, JPV, Arnett, JE, Ortega, DG, Schmidt, RJ, Johnson, GO, Natarajan, SK, and Housh, TJ. Effects of high-intensity, eccentric-only muscle actions on serum biomarkers of collagen degradation and synthesis. J Strength Cond Res 37(9): 1729-1737, 2023-The purpose of this study was to examine the effects of high-intensity, eccentric-only muscle actions of the leg extensors on (a) serum biomarkers of collagen degradation (hydroxyproline [HYP] and C-terminal telopeptide of type I collagen [C1M]) and synthesis (pro-c1α1) and (b) the time course of changes in maximal voluntary isometric contraction (MVIC) and ratings of muscle soreness after the eccentric-only exercise bout. Twenty-five recreationally active men (mean ± SD: age = 21.2 ± 2.0 years) completed 5 sets of 10 bilateral, eccentric-only dynamic constant external resistance muscle actions of the leg extensors at a load of 110% of their concentric leg extension 1 repetition maximum. Analysis of variances (p < 0.05) and a priori planned pairwise comparisons using Bonferroni corrected (p < 0.0167) paired t tests were used to examine mean changes in blood biomarkers from baseline to 48 hours postexercise as well as in MVIC and soreness ratings immediately, 24 hours, and 48 hours postexercise. There were increases in HYP (3.41 ± 2.37 to 12.37 ± 8.11 µg·ml-1; p < 0.001) and C1M (2.50 ± 1.05 to 5.64 ± 4.89 µg·L-1; p = 0.003) from preexercise to 48 hours postexercise, but no change in pro-c1α1. Maximal voluntary isometric contraction declined immediately after the exercise bout (450.44 ± 72.80 to 424.48 ± 66.67 N·m; p = 0.002) but recovered 24 hours later, whereas soreness was elevated immediately (6.56 ± 1.58; p < 0.001), 24 hours (3.52 ± 1.53; p < 0.001), and 48 hours (2.60 ± 1.32; p = 0.001) postexercise. The eccentric-only exercise bout induced increases in collagen degradation but had no effect on collagen synthesis. These findings provide information for clinicians to consider when prescribing exercise after an acute injury or surgery.
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Ejercicio Físico , Mialgia , Masculino , Humanos , Adulto Joven , Adulto , Biomarcadores , Colágeno , MúsculosRESUMEN
This study examined the effects of joint angle (JA) on maximal voluntary isometric contraction (MVIC) and neuromuscular responses following fatiguing tasks anchored to RPE. Nine men (mean ± SD: age = 20.7 ± 1.2 yrs) performed forearm flexion MVICs at elbow JAs of 75° and 125° before and after sustained, isometric forearm flexion tasks to failure at fatiguing joint angles (FJA) of 75° and 125° anchored to RPE = 8. The amplitude and frequency of the electromyographic and mechanomyographic signals were recorded. Neuromuscular efficiency was calculated by dividing normalized torque by normalized electromyographic amplitude. A dependent t-test was used to assess the mean difference for time to task failure (TTF) between FJA. Repeated measure ANOVAs were used to assess mean differences for pre-test to post-test MVIC and neuromuscular responses. There was no significant difference between FJA for TTF (p = 0.223). The MVIC (collapsed across FJA and MVIC JA) decreased from pre-test to post-test (51.1 ± 5.0 vs. 45.3 ± 5.6 Nm, p < 0.001). Normalized neuromuscular parameters remained unchanged (p > 0.05). The FJA resulted in similar torque and neuromuscular responses, and the decreases in MVIC were not tracked by changes in the neuromuscular parameters. Thus, the neuromuscular parameters were not sensitive to fatigue, and pre-test to post-test measures may be compared between different FJA.
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The present study examined the effect of anchor schemes on the time to task failure (TTF), performance fatigability, neuromuscular responses, and the perceived sensations that contributed to task termination following the sustained, isometric forearm flexion tasks. Eight women completed sustained, isometric forearm flexion tasks anchored to RPE = 8 (RPEFT) and the torque (TRQFT) that corresponded to RPE = 8. The subjects performed pre-test and post-test maximal isometric contractions to quantify performance fatigability and changes in electromyographic amplitude (EMG AMP) and neuromuscular efficiency (NME). In addition, the subjects completed a post-test questionnaire (PTQ) to quantify the contributions of perceived sensations to task termination. Repeated measure ANOVAs were used to assess the mean differences for TTF, performance fatigability, and neuromuscular responses. Wilcoxon Signed Rank Tests were used to assess the differences between anchor schemes for the average values from the PTQ item scores. For TTF, the RPEFT was longer than the TRQFT (174.9 ± 85.6 vs. 65.6 ± 68.0 s; p = 0.006). Collapsed across the anchor scheme, there were decreases in torque (23.7 ± 5.5 Nm vs. 19.6 ± 4.9 Nm; p < 0.001) and NME (1.00 ± 0.00 vs. 0.76 ± 0.15; p = 0.003). There were no significant (p > 0.577) changes for EMG AMP. For the PTQ, there were no differences (p > 0.05) between anchor schemes. There were, however, inter-individual differences in the response scores. The current findings indicated that performance fatigability was likely due to peripheral fatigue (based on NME), not central fatigue (based on EMG AMP). Furthermore, the use of a PTQ may serve as a simple tool to assess the contributions of perceived sensations to task termination.
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PURPOSE: The purpose of the present study was to examine the interactions between perceived fatigability and performance fatigability in women and men by utilizing the RPE-Clamp model to assess the fatigue-induced effects of a sustained, isometric forearm flexion task anchored to RPE = 8 on time to task failure (TTF), torque, and neuromuscular responses. METHODS: Twenty adults (10 men and 10 women) performed two, 3 s forearm flexion maximal voluntary isometric contractions (MVICs) followed by a sustained, isometric forearm flexion task anchored to RPE = 8 using the OMNI-RES (0-10) scale at an elbow joint angle of 100°. Electromyographic amplitude (EMG AMP) was recorded from the biceps brachii. Torque and EMG AMP values resulting from the sustained task were normalized to the pretest MVIC. Neuromuscular efficiency was defined as NME = normalized torque/normalized EMG AMP. Mixed factorial ANOVAs and Bonferroni corrected dependent t tests and independent t tests were used to examine differences across time and between sex for torque and neuromuscular parameters. RESULTS: There were no differences between the women and men for the fatigue-induced decreases in torque, EMG AMP, or NME, and the mean decreases (collapsed across sex) were 50.3 ± 8.6 to 2.8 ± 2.9% MVIC, 54.7 ± 12.0 to 19.6 ± 5.3% MVIC, and 0.94 ± 0.19 to 0.34 ± 0.16, respectively. Furthermore, there were no differences between the women and men for TTF (251.8 ± 74.1 vs. 258.7 ± 77.9 s). CONCLUSION: The results suggested that the voluntary reductions in torque to maintain RPE and the decreases in NME were likely due to group III/IV afferent feedback from peripheral fatigue that resulted in excitation-contraction coupling failure.
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Fatiga Muscular , Músculo Esquelético , Masculino , Adulto , Humanos , Femenino , Electromiografía , Músculo Esquelético/fisiología , Fatiga Muscular/fisiología , Extremidad Superior , Contracción Isométrica/fisiología , TorqueRESUMEN
ABSTRACT: Salmon, OF, Housh, TJ, Hill, EC, Keller, JL, Anders, JPV, Johnson, GO, Schmidt, RJ, and Smith, CM. Changes in neuromuscular response patterns after 4 weeks of leg press training during isokinetic leg extensions. J Strength Cond Res 37(7): e405-e412, 2023-The purpose of this study was to identify velocity-specific changes in electromyographic root mean square (EMG RMS), EMG frequency (EMG MPF), mechanomyographic RMS (MMG RMS), and MMG MPF during maximal unilateral isokinetic muscle actions performed at 60° and 240°·s -1 velocities within the right and left vastus lateralis (VL) after 4 weeks of dynamic constant external resistance (DCER) bilateral leg press training. Twelve resistance-trained men (age: mean ± SD = 21.4 ± 3.6 years) visited the laboratory 3d·wk -1 to perform resistance training consisting of 3 sets of 10 DCER leg presses. Four, three-way analysis of variance were performed to evaluate changes in neuromuscular responses (EMG RMS, EMG MPF, MMG RMS, and MMG MPF) from the right and left VL during 1 single-leg maximal isokinetic leg extension performed at 60° and 240°·s -1 before and after 4 weeks of DCER leg press training ( p < 0.05). The results indicated a 36% increase in EMG RMS for the right leg, as well as a 23% increase in MMG RMS and 10% decrease in MMG MPF after training, collapsed across velocity and leg. In addition, EMG RMS was 65% greater in the right leg than the left leg following training, whereas EMG MPF was 11% greater for the left leg than the right leg throughout training. Thus, 4 weeks of DCER leg press training provides sufficient stimuli to alter the neuromuscular activation process of the VL but not velocity-specific neuromuscular adaptations in trained males.
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Pierna , Músculo Esquelético , Masculino , Humanos , Músculo Esquelético/fisiología , Electromiografía/métodos , Pierna/fisiología , Contracción Muscular/fisiología , TorqueRESUMEN
OBJECTIVE: This study examined the time course of changes in torque and electromyographic (EMG) and mechanomyographic (MMG) responses during a sustained isometric task anchored to a constant perception of exertion (RPE). METHODS: Twelve college-aged men performed an isometric forearm flexion task to failure anchored to RPE=7 (OMNI-RES scale). The amplitude (AMP) and frequency (MPF) of the EMG and MMG signals from the biceps brachii were recorded. Repeated measures ANOVAs were used to examine differences for the normalized (%MVIC) torque and neuromuscular parameters. RESULTS: The time to task failure (TTF) was 678.0±468.1s. Torque decreased significantly (p<0.001, ηp2=0.774) across time and all subjects reduced torque to zero. Post-hoc comparisons indicated that the torque values from 20-100% TTF were less than the value at 10% TTF. There were no significant (p>0.05) changes from 10-100% TTF for the EMG and MMG parameters. CONCLUSION: We hypothesize that RPE was maintained by various mechanisms throughout the task: group III/IV afferent neurons, adequate blood flow, and a combination of reduced contractile efficiency, collective afferent feedback (group III/IV afferents) from muscles involved with forearm flexion, and motivation that resulted in an initial decrease, plateau, and final decline in torque to zero, respectively.
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Antebrazo , Esfuerzo Físico , Masculino , Humanos , Adulto Joven , Torque , Extremidad Superior , FatigaRESUMEN
BACKGROUND: Antagonist activation may contribute to fatigue-induced decreases in torque while assisting in the maintenance of joint stability. This study utilized a reciprocal, slow velocity (60°·s-1) forearm flexion and extension fatiguing task to examine the contributions of coactivation to torque production at slow and moderate (180°·s-1) velocities, as well as during a maximal voluntary isometric contraction (MVIC). METHODS: Twelve recreationally active men (mean ± SD: age = 21.7 ± 1.6 years; body mass = 83.5 ± 8.8 kg; height = 179.4 ± 5.2 cm) completed isokinetic (60 and 180°·s-1) and isometric pre-testing of forearm flexion and extension, followed by 50 maximal, reciprocal, isokinetic muscle actions at 60°·s-1, followed by post-testing. The amplitude (AMP) of the electromyographic (EMG) signals from the biceps and triceps brachii were simultaneously recorded. Torque and EMG AMP were normalized to the corresponding values from the pre-testing peak torque movements. Repeated measures ANOVAs and pairwise comparisons were used to identify mean changes in torque, EMG AMP, and coactivation ratios. RESULTS: The torque analyses indicated greater (p < 0.03) decreases for 180°·s-1 (24%) and MVIC (23%) than 60°·s-1 (14%) for forearm flexion. For forearm extension, there were no differences (p > 0.05) in fatigability between velocities. For EMG AMP there were no changes (p > 0.05) from pre- to post-testing for any velocity or movement. There were no changes (p > 0.05) in the coactivation ratio for forearm flexion, but significant increases (13.6 ± 6.6 to 16.9 ± 6.0; p = 0.003) for forearm extension, collapsed across Velocity. CONCLUSIONS: There was velocity- and movement-specific fatigability for forearm flexion and extension. The parallel, fatigue-induced EMG AMP responses indicated that coactivation did not contribute to the decreases in torque and would not affect elbow joint stability.
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Contracción Isométrica , Fatiga Muscular , Adulto , Humanos , Masculino , Adulto Joven , Electromiografía , Contracción Isométrica/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , TorqueRESUMEN
Giant cell tumors are uncommonly found within the craniofacial skeleton, and of those within the head and neck, are exceedingly rare in the maxilla. Here the authors present 2 cases of large, maxillary giant cell tumors: one presenting with mass-effect symptoms and another presenting from incidental findings on routine orthodontic care. Both patients were treated surgically with transoral and endoscopic transnasal excision and demonstrated favorable surgical results. One patient demonstrated no recurrence after 9 years and the other patient was disease free after 4 years. The authors end by discussing the role of emerging biologic agents, such as denosumab, for treating giant cell tumors of the jaws.
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Conservadores de la Densidad Ósea , Neoplasias Óseas , Tumor Óseo de Células Gigantes , Factores Biológicos , Neoplasias Óseas/cirugía , Niño , Legrado/métodos , Denosumab , Tumor Óseo de Células Gigantes/patología , Humanos , Maxilar/patología , Estudios RetrospectivosRESUMEN
ABSTRACT: Keller, JL, Housh, TJ, Hill, EC, Smith, CM, Schmidt, RJ, and Johnson, GO. Are there sex-specific neuromuscular or force responses to fatiguing isometric muscle actions anchored to a high perceptual intensity? J Strength Cond Res 36(1): 156-161, 2022-The purpose of this study was to use the ratings of perceived exertion (RPE) clamp model to examine sex-specific changes in neuromuscular responses and force after a sustained isometric leg extension muscle action anchored to RPE = 8. Twenty adults (10 men and 10 women) performed sustained, isometric leg extension muscle actions at RPE = 8. Electromyographic (EMG) and mechanomyographic signals were recorded from the dominant leg. Neuromuscular and force values resulting from the sustained muscle action were normalized to pretest maximal voluntary isometric contractions (MVICs). The level of significance set for the study was p ≤ 0.05. The pretest MVIC was significantly (p < 0.001) greater (averaged across sex) than posttest MVIC force (55.5 ± 10.0 vs. 47.6 ± 11.1 kg). There was a significant (p < 0.01) decrease from pretest (95.4 ± 7.7 Hz) to posttest (76.2 ± 5.9 Hz) in EMG mean power frequency (MPF) for the men. The normalized force (averaged across sex) decreased significantly (p < 0.001) from the initial timepoint (57.1 ± 16.4%) to the final timepoint (44.3 ± 15.7%) of the sustained muscle action. Normalized EMG MPF (averaged across sex) decreased significantly (p = 0.001) from the initial timepoint (96.4 ± 17.5%) to final timepoint (87.8 ± 18.1%). The men and women exhibited similar fatigue-induced changes in force and neuromuscular parameters; therefore, these findings did not indicate different sex-specific responses after the fatiguing task anchored to a high perception of exertion. The force corresponding to RPE = 8 did not match the anticipated value; so, RPE and percentages of MVIC cannot be used interchangeably, and sustained isometric muscle actions anchored to RPE may elicit unique neuromuscular adaptations.