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1.
J Int Soc Sports Nutr ; 18(1): 60, 2021 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-34503541

RESUMO

BACKGROUND: Numerous studies have demonstrated the efficacy of creatine supplementation for improvements in exercise performance. Few studies, however, have examined the effects of phosphocreatine supplementation on exercise performance. Furthermore, while polyphenols have antioxidant and anti-inflammatory properties, little is known regarding the influence of polyphenol supplementation on muscular strength, power, and endurance. Thus, the purpose of the present study was to compare the effects of 28 days of supplementation with phosphocreatine disodium salts plus blueberry extract (PCDSB), creatine monohydrate (CM), and placebo on measures of muscular strength, power, and endurance. METHODS: Thirty-three men were randomly assigned to consume either PCDSB, CM, or placebo for 28 days. Peak torque (PT), average power (AP), and percent decline for peak torque (PT%) and average power (AP%) were assessed from a fatigue test consisting of 50 maximal, unilateral, isokinetic leg extensions at 180°·s- 1 before and after the 28 days of supplementation. Individual responses were assessed to examine the proportion of subjects that exceeded a minimal important difference (MID). RESULTS: The results demonstrated significant (p < 0.05) improvements in PT for the PCDSB and CM groups from pre- (99.90 ± 22.47 N·m and 99.95 ± 22.50 N·m, respectively) to post-supplementation (119.22 ± 29.87 N·m and 111.97 ± 24.50 N·m, respectively), but no significant (p = 0.112) change for the placebo group. The PCDSB and CM groups also exhibited significant improvements in AP from pre- (140.18 ± 32.08 W and 143.42 ± 33.84 W, respectively) to post-supplementation (170.12 ± 42.68 W and 159.78 ± 31.20 W, respectively), but no significant (p = 0.279) change for the placebo group. A significantly (p < 0.05) greater proportion of subjects in the PCDSB group exceeded the MID for PT compared to the placebo group, but there were no significant (p > 0.05) differences in the proportion of subjects exceeding the MID between the CM and placebo groups or between the CM and PCDSB groups. CONCLUSIONS: These findings indicated that for the group mean responses, 28 days of supplementation with both PCDSB and CM resulted in increases in PT and AP. The PCDSB, however, may have an advantage over CM when compared to the placebo group for the proportion of individuals that respond favorably to supplementation with meaningful increases in muscular strength.


Assuntos
Força Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Fosfocreatina/farmacologia , Resistência Física/efeitos dos fármacos , Extratos Vegetais/farmacologia , Mirtilos Azuis (Planta)/química , Creatina , Suplementos Nutricionais , Método Duplo-Cego , Humanos , Masculino , Torque , Adulto Jovem
2.
Eur J Appl Physiol ; 2021 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-34432149

RESUMO

PURPOSE: Literature is conflicted on whether electromechanical delay durations decrease following resistance training programs. Therefore, the aim of this study is to examine the contributions and durations of the electrochemical (EMDE-M) and mechanical (EMDM-F) components to the overall electromechanical delay (EMDE-F) during step isometric muscle actions following 4-weeks of structured, multi-joint, lower-body variable resistance training (VRT) program. METHODS: Twelve men performed 4-weeks of VRT leg press training utilizing combination of steel plates (80% total load) and elastic bands (20% total load). Training consisted of 3 sets of 10 repetitions at a 10 repetition maximum load, 3 day week-1 for 4-weeks. EMDE-M, EMDM-F, and EMDE-F was measured at Baseline, Week-2, and Week-4 during voluntary step isometric muscle actions (20, 40, 60, 80, and 100% of maximal voluntary isometric contraction) from the vastus lateralis using electromyographic, mechanomyographic, and force signals. RESULTS: The EMDE-M, EMDM-F, and EMDE-F exhibited decreases in duration following 4-weeks of VRT. In addition, EMDE-M contributed significantly less (42-47%) than EMDM-F (53-58%) to the total duration of EMDE-F across the 4-weeks of VRT. CONCLUSIONS: These findings indicated that a structured, VRT program utilizing multi-joint exercise was sufficient to induce decreases in the electrochemical and mechanical processes associated with step isometric muscle contractions. In addition, the utilization of the electromyographic, mechanomyographic, and force signals were capable of quantifying electrochemical and mechanical component changes associated with voluntary muscle contraction. Thus, EMDE-M, EMDM-F, and EMDE-F can be useful in quantifying physiological changes in athletic, clinical, and applied research interventions.

3.
J Sports Sci Med ; 20(3): 391-397, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34267577

RESUMO

The purpose of the present study was to examine the influence of an acute bout of high-intensity resistance exercise on measures of cognitive function. Ten men (Mean ± SD: age = 24.4 ± 3.2 yrs; body mass = 85.7 ± 11.8 kg; height = 1.78 ± 0.08 m; 1 repetition maximum (1RM) = 139.0 ± 24.1 kg) gave informed consent and performed a high-intensity 6 sets of 10 repetitions of barbell back squat exercise at 80% 1RM with 2 minutes rest between sets. The Automated Neuropsychological Assessment Metrics (ANAM) was completed to assess various cognitive domains during the familiarization period, immediately before, and immediately after the high-intensity resistance exercise bout. The repeated measures ANOVAs for throughput scores (r·m-1) demonstrated significant mean differences for the Mathematical Processing task (MTH; p < 0.001, η2 p = 0.625) where post hoc pairwise comparisons demonstrated that the post-fatigue throughput (32.0 ± 8.8 r·m-1) was significantly greater than the pre-fatigue (23.8 ± 7.4 r·m-1, p = 0.003, d = 1.01) and the familiarization throughput (26.4 ± 5.3 r·m-1, p = 0.024, d = 0.77). The Coded Substitution-Delay task also demonstrated significant mean differences (CDD; p = 0.027, η2 p = 0.394) with post hoc pairwise comparisons demonstrating that the post-fatigue throughput (49.3 ± 14.4 r·m-1) was significantly less than the pre-fatigue throughput (63.2 ± 9.6 r·m-1, p = 0.011, d = 1.14). The repeated measures ANOVAs for reaction time (ms) demonstrated significant mean differences for MTH (p < 0.001, η2 p = 0.624) where post hoc pairwise comparisons demonstrated that the post-fatigue reaction time (1885.2 ± 582.8 ms) was significantly less than the pre-fatigue (2518.2 ± 884.8 ms, p = 0.005, d = 0.85) and familiarization (2253.7 ± 567.6 ms, p = 0.009, d = 0.64) reaction times. The Go/No-Go task demonstrated significant mean differences (GNG; p = 0.031, η2 p = 0.320) with post hoc pairwise comparisons demonstrating that the post-fatigue (285.9 ± 16.3 ms) was significantly less than the pre-fatigue (298.5 ± 12.1 ms, p = 0.006, d = 0.88) reaction times. High-intensity resistance exercise may elicit domain-specific influences on cognitive function, characterized by the facilitation of simple cognitive tasks and impairments of complex cognitive tasks.


Assuntos
Cognição/fisiologia , Treinamento de Força/métodos , Adulto , Atenção , Frequência Cardíaca , Humanos , Ácido Láctico/sangue , Masculino , Memória , Rememoração Mental , Fadiga Muscular/fisiologia , Força Muscular , Tempo de Reação , Adulto Jovem
4.
Clin Physiol Funct Imaging ; 41(5): 452-460, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34192417

RESUMO

The purpose of the present study was to examine the acute changes in muscle swelling (as assessed by muscle thickness and echo intensity) and muscle blood flow associated with an acute bout of low-load blood flow restriction (LLBFR) and low-load non-blood flow restriction (LL) exercise. Twenty women (mean ± SD; 22 ± 2years) volunteered to perform an acute exercise bout that consisted of 75 (1 × 30, 3 × 15) isokinetic, reciprocal, concentric-only, submaximal (30% of peak torque), forearm flexion and extension muscle actions. Pretest, immediately after (posttest), and 5-min after (recovery) completing the 75 repetitions, muscle thickness and echo intensity were assessed from the biceps brachii and triceps brachii muscles and muscle blood flow was assessed from the brachial artery. There were no between group differences for any of the dependent variables, but there were significant simple and main effects for muscle and time. Biceps and triceps brachii muscle thickness increased from pretest (2.13 ± 0.39 cm and 1.88 ± 0.40 cm, respectively) to posttest (2.58 ± 0.49 cm and 2.17 ± 0.43 cm, respectively) for both muscles and remained elevated for the biceps brachii (2.53 ± 0.43 cm), but partially returned to pretest levels for the triceps brachii (2.06 ± 0.41 cm). Echo intensity and muscle blood flow increased from pretest (98.0 ± 13.6 Au and 94.5 ± 31.6 ml min-1 , respectively) to posttest (109.2 ± 16.9 Au and 312.2 ± 106.5 ml min-1 , respectively) and pretest to recovery (110.1 ± 18.3 Au and 206.7 ± 92.9 ml min-1 , respectively) and remained elevated for echo intensity, but partially returned to pretest levels for muscle blood flow. The findings of the present study indicated that LLBFR and LL elicited comparable acute responses as a result of reciprocal, concentric-only, forearm flexion and extension muscle actions.


Assuntos
Braço , Músculo Esquelético , Edema , Exercício Físico , Feminino , Humanos , Músculo Esquelético/diagnóstico por imagem , Torque
5.
Eur J Appl Physiol ; 121(8): 2243-2252, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33893835

RESUMO

PURPOSE: The purpose of this study was to examine the composite, intra-individual, and inter-individual patterns of responses for deoxygenated hemoglobin and myoglobin (deoxy[heme]), oxygenated hemoglobin and myoglobin (oxy[heme]), total hemoglobin and myoglobin (total[heme]), and tissue saturation index (StO2%) during fatiguing, maximal, isokinetic, unilateral, and bilateral leg extensions. METHODS: Nine men (Mean ± SD; age = 21.9 ± 2.4 years; height = 181.8 ± 11.9 cm; body mass = 85.8 ± 6.2 kg) performed 50 unilateral and bilateral maximal, concentric, isokinetic leg extensions at 180° s-1 on two separate visits. The muscle oxygenation parameters assessed with near-infrared spectroscopy from the dominant leg and isokinetic torque were averaged for 2 consecutive repetitions at 5 repetition intervals. Separate 2 (Condition [Unilateral and Bilateral]) × 10 (Repetition [5-50]) repeated measures ANOVAs were performed to examine mean differences for normalized isokinetic torque and each muscle oxygenation parameter. Intra- and inter-individual differences were examined with polynomial regression analyses. RESULTS: For normalized isokinetic torque, the unilateral condition (56.3 ± 10.5%) exhibited greater performance fatigability than the bilateral condition (45.0 ± 18.7%). Collapsed across Condition, deoxy[heme] exhibited an increase (p < 0.001), while StO2% exhibited a decrease (p < 0.001). The bilateral condition exhibited a more sustained decline in oxy[heme] than the unilateral condition (p = 0.005). Deoxy[heme], oxy[heme], and total[heme] exhibited substantial intra- and inter-individual differences for the fatigue-induced patterns of response. CONCLUSION: The present findings indicated that the greater performance fatigability for unilateral versus bilateral fatiguing, maximal, isokinetic leg extensions was not attributable to differences in muscle oxygenation. Future studies of muscle oxygenation should report individual and composite fatigue-induced patterns of responses due to the substantial intra- and inter-individual variabilities.

6.
J Musculoskelet Neuronal Interact ; 21(1): 4-12, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-33657751

RESUMO

OBJECTIVES: The purpose of the present study was to compare the fatigue-induced changes in performance fatigability, bilateral deficit, and patterns of responses for the electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF), during unilateral and bilateral maximal, fatiguing leg extensions. METHODS: Nine men (Mean±SD; age =21.9±2.4 yrs; height =181.8±11.9 cm; body mass =85.8±6.2 kg) volunteered to perform 50 consecutive maximal, bilateral (BL), unilateral dominant (DL), and unilateral non-dominant (NL) isokinetic leg extensions at 180°·s-1, on 3 separate days. Electromyographic and MMG signals from both vastus lateralis (VL) muscles were recorded. Repeated measures ANOVAs were utilized to examine mean differences in normalized force, EMG AMP, EMG MPF, MMG AMP, MMG MPF and the bilateral deficit. RESULTS: The results demonstrated a Condition × Repetition interaction for normalized force (p=0.004, η2p=0.222) and EMG MPF (p=0.034, η2p=0.214) and main effects for Repetition for EMG AMP (p=0.019, η2p=0.231), MMG AMP (p<0.001, η2p=0.8550), MMG MPF (p=0.009, η2p=0.252), and the bilateral deficit (p<0.001, η2p=0.366). CONCLUSIONS: The findings demonstrated less performance fatigability during the BL than the unilateral tasks, likely due to a reduced relative intensity via interhemispheric inhibition that attenuated the development of excitation-contraction coupling failure during the BL task.

7.
Eur J Appl Physiol ; 121(4): 1111-1124, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33484333

RESUMO

PURPOSE: The present study examined the magnitude of performance fatigability as well as the associated limb- and intensity-specific neuromuscular patterns of responses during sustained, bilateral, isometric, leg extensions above and below critical force (CF). METHODS: Twelve women completed three sustained leg extensions (1 below and 2 above CF) anchored to forces corresponding to RPE = 1, 5, and 8 (10-point scale). During each sustained leg extension, electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) were assessed from each vastus lateralis in 5% of time-to-exhaustion (TTE) segments. Before and after each sustained leg extension, the subjects completed maximal voluntary isometric contractions (MVIC), and the percent decline was defined as performance fatigability. Polynomial regression was used to define the individual and composite neuromuscular and force values versus time relationships. Repeated-measures ANOVAs assessed differences in performance fatigability and TTE. RESULTS: The grand mean for performance fatigability was 10.1 ± 7.6%. For TTE, the repeated-measures ANOVA indicated that there was a significant (p < 0.05) effect for Intensity, such that RPE = 1 > 5 > 8. There were similar neuromuscular patterns of response between limbs as well as above and below CF. EMG MPF, however, exhibited decreases only above CF. CONCLUSIONS: Performance fatigability was unvarying above and below CF as well as between limbs. In addition, there were similar fatigue-induced motor unit activation strategies above and below CF, but peripheral fatigue likely contributed to a greater extent above CF.

8.
J Musculoskelet Neuronal Interact ; 20(3): 325-331, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32877969

RESUMO

OBJECTIVES: This study examined performance fatigability and the patterns of neuromuscular responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during bilateral (BL) and unilateral (UL) maximal, isokinetic leg extensions. METHODS: Peak torque for each repetition and EMG and MMG signals from the non-dominant vastus lateralis were recorded in 11 men during 50 BL and UL maximal, concentric, isokinetic leg extensions at 60o·s-1 that were performed on separate days. Separate repeated measures ANOVAs were performed to examine the normalized isokinetic torque and neuromuscular parameters. RESULTS: Normalized isokinetic peak torque demonstrated a significant Conditions by Repetition interaction (p<0.001, η2p= 0.594). There were no interactions, but significant main effects for Repetition with increases in EMG AMP (p<0.001; η2p=0.255) and decreases in EMG MPF (p<0.001; η2p=0.650), MMG AMP (p<0.001; η2p=0.402), and MMG MPF (p<0.001; η2p=0.796). In addition, EMG MPF and MMG AMP demonstrated main effects for Condition (p=0.031; η2p=0.387 and p=0.002; η2p=0.64, respectively) with the BL exhibiting greater values than UL leg extensions for both parameters. CONCLUSIONS: The current findings indicated greater performance fatigability during UL versus BL leg extensions, but similar patterns of neuromuscular responses consistent with the Muscle Wisdom Hypothesis.

9.
J Electromyogr Kinesiol ; 50: 102367, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31711012

RESUMO

The purpose of this study was to compare isokinetic peak torque and the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG), amplitude (AMP) and mean power frequency (MPF) for bilateral (BL) versus unilateral (UL), maximal, isokinetic leg extensions. Eleven recreationally trained women (Mean ±â€¯SD: age 22.9 ±â€¯0.9 yrs; body mass 60.5 ±â€¯10.1 kg; height 167.2 ±â€¯6.4 cm) performed 50 maximal, BL and UL isokinetic leg extensions at 60°â€¯s-1 on separate days. Electromyographic and MMG signals from the vastus lateralis of the nondominant leg were recorded. Five separate 2 (Condition [BL and UL]) × 10 (Repetitions [5-50]) repeated measures ANOVAs were performed to examine normalized EMG AMP, EMG MPF, MMG AMP, MMG MPF, and isokinetic torque. The results indicated no significant interactions or main effects for EMG AMP and MMG AMP. There were significant interactions for normalized isokinetic peak torque (p < 0.001, η2p = 0.493) and MMG MPF (p = 0.003, η2p = 0.234). For EMG MPF, there was no significant interaction, but significant main effects for Condition (p = 0.003, η2p = 0.607) and Repetitions (p < 0.001, η2p = 0.805). The current findings demonstrated greater performance fatigability for UL than BL leg extensions. Both modalities exhibited similar patterns of neuromuscular responses that were consistent with the Muscular Wisdom hypothesis.


Assuntos
Perna (Membro)/fisiologia , Fadiga Muscular , Músculo Esquelético/fisiologia , Adulto , Testes Diagnósticos de Rotina , Feminino , Lateralidade Funcional , Humanos , Contração Muscular , Torque
10.
J Funct Morphol Kinesiol ; 5(1)2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-33467220

RESUMO

Previous studies have demonstrated that ayurvedic ingredients exhibit ergogenic (performance enhancing) properties, however, no previous studies have examined the ergogenic potential of Asparagus racemosus. The purpose of the present study was to examine the ergogenic efficacy of supplementation with 500 mg·d-1 of A. racemosus during bench press training. Eighteen recreationally trained men (mean ± SD; age = 20.4 ± 0.5 yrs; height = 179.7 ± 1.5 cm; weight = 84.7 ± 5.7 kg) were randomly assigned either 500 mg·d-1 of A. racemosus (n = 10) or placebo (n = 8). An overlapping sample of 10 participants were used to determine test-retest reliability. Pre- and post-training testing included bench press with one repetition maximum (1RM) and repetitions to failure at 70% of pre-training 1RM. The participants performed two sets of bench press to failure three times a week for eight weeks. Independent t-tests, Analyses of covariance (ANCOVA), and regression analyses were used to analyze the dependent variables. The results demonstrated greater mean percentage (14.3 ± 7.7% vs. 7.8 ± 4.5%; p = 0.048) and individual (80% vs. 50%) increases in 1RM, mean (17.5 ± 2.2 repetitions vs. 15.2 ± 2.2 repetitions; p = 0.044) and individual (80% vs. 38%) increases in repetitions to failure, and a greater rate of increase in training loads for the Asparagus racemosus group than the placebo group. In conjunction with bench press training, supplementation with A. racemosus provided ergogenic benefits compared to placebo.

11.
Somatosens Mot Res ; 36(3): 223-229, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31474178

RESUMO

Purpose: The purpose of this study was to examine the changes in reflex-electromechanical delay (EMD) as a result of 2- and 4-wks of variable resistance training (VRT) or dynamic constant external resistance (DCER) leg press training. Material and Methods: Thirty-six men were randomised into either the Control, DCER, or VRT groups. The DCER and VRT groups performed 3 sets of 10 leg press repetitions 3-d·wk-1 for 4-wks. Reflex-EMD was measured at Baseline, Week-2, and Week-4. Results: The reflex-EMD durations decreased from Baseline at Week-2 and Week-4 for the VRT group, but not the DCER or Control groups. The reflex response < electrochemical process < mechanical process < total reflex-EMD for all groups. Conclusions: VRT elicited greater reflex adaptations compared to DCER training which indicated that VRT may be beneficial to incorporate into training or physical therapy programmes for pilots, soldiers, elderly, athletes, or professions that require quick reflexes and response times.


Assuntos
Adaptação Fisiológica/fisiologia , Fenômenos Biomecânicos/fisiologia , Perna (Membro)/fisiologia , Músculo Esquelético/fisiologia , Reflexo de Estiramento/fisiologia , Treinamento de Força/métodos , Adulto , Humanos , Masculino , Adulto Jovem
12.
Sports (Basel) ; 7(7)2019 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-31323817

RESUMO

The purpose of this study was to compare the composite, inter-individual, and intra-individual differences in the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during fatiguing, maximal, bilateral, and isokinetic leg extension muscle actions. Thirteen recreationally active men (age = 21.7 ± 2.6 years; body mass = 79.8 ± 11.5 kg; height = 174.2 ± 12.7 cm) performed maximal, bilateral leg extensions at 180°·s-1 until the torque values dropped to 50% of peak torque for two consecutive repetitions. The EMG and MMG signals from the vastus lateralis (VL) muscles of both limbs were recorded. Four 2(Leg) × 19(time) repeated measures ANOVAs were conducted to examine mean differences for EMG AMP, EMG MPF, MMG AMP, and MMG MPF between limbs, and polynomial regression analyses were performed to identify the patterns of neuromuscular responses. The results indicated no significant differences between limbs for EMG AMP (p = 0.44), EMG MPF (p = 0.33), MMG AMP (p = 0.89), or MMG MPF (p = 0.52). Polynomial regression analyses demonstrated substantial inter-individual variability. Inferences made regarding the patterns of neuromuscular responses to fatiguing and bilateral muscle actions should be considered on a subject-by-subject basis.

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