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1.
J Strength Cond Res ; 34(1): 73-78, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29889776

RESUMO

Williams, MR Jr, Hendricks, DS, Dannen, MJ, Arnold, AM, and Lawrence, MA. Activity of shoulder stabilizers and prime movers during an unstable overhead press. J Strength Cond Res 34(1): 73-78, 2020-Overhead reaching is a common movement that relies heavily on muscles for dynamic stability. Stabilizer muscle activation increased during squatting and bench pressing with an unstable load, but the overhead press (OHP) has yet to be examined. The purpose of this study is to compare muscle activity of the shoulder stabilizers and prime movers and excursions of the center of pressure (CoP) during the OHP in 2 unstable and one stable conditions. Twelve men (aged 25.3 ± 2.7 years, mass: 91.5 ± 8.4 kg, height: 1.81 ± 0.06 m) pressed 50% of their 1 repetition maximum for 10 repetitions over 3 conditions: a straight stable barbell (SS), a straight unstable (SU) barbell with kettlebells suspend by elastic bands, and an unstable Earthquake (EU) bar with kettlebells suspended by elastic bands. Activity of the shoulder stabilizers and prime movers were measured via surface and indwelling electromyography. Center of pressure excursion of the right foot was also measured. A multivariate analysis was used to determine significant differences between conditions. Pressing with the EQ increased activation of the biceps brachii, erector spinae, latissimus dorsi, pectoralis major, rectus abdominus, rhomboids, and serratus anterior over the SS condition, whereas only the SU condition increased activation in the erector spinae and latissimus dorsi muscles. The EQ condition produced greater CoP excursion (35.3 ± 7.9% foot length) compared with the SU (28.0 ± 7.2% foot length) and SS (22.2 ± 6.3% foot length) conditions. Therefore, the EU condition may be an effective exercise to activate scapular stabilizers.

2.
Cortex ; 122: 123-130, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30527265

RESUMO

Slower reaction times to targets presented at a previously cued or attended location are often attributed to inhibition of return (IOR). It has been suggested that IOR affects a process at the output end of processing continuum when it is generated while the oculomotor system is activated. Following the path set by Kavyani, Farsi, Abdoli, and Klein (2017) we used the locus of slack logic embedded in the psychological refractory period (PRP) paradigm to test this idea. We generated what we expected would be the output form of IOR by beginning each with participants making a target directed saccade which was followed by two tasks. Task 1, was a 2-choice auditory discrimination task and Task 2 was a 2-choice visual localization task. We varied the interval between the onsets of the two targets associated with these two tasks (using TTOAs of 200, 400, or 800 msec). As expected the visual task suffered from a robust PRP effect (substantially delayed RTs at the shorter TTOAs). There was also a robust IOR effect with RTs to localize visual targets being slower when the targets were presented at a previously fixated location. Importantly, and in striking to our previous results wherein we generated the input form of IOR, in the present study there was an additive effect between IOR and TTOA on RT2. As implied by the locus of slack logic, we therefore conclude that the form of IOR generated when the oculomotor system is activated affects a late stage of processing. Converging evidence for this conclusion, from a variety of neuroscientific methods, is presented and the dearth of such evidence about the input form of IOR is noted.

3.
Vision (Basel) ; 3(2)2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31735832

RESUMO

Existing research has found that spatial attention alters how various stimulus properties are perceived (e.g., luminance, saturation), but few have explored whether it improves the accuracy of perception. To address this question, we performed two experiments using modified Posner cueing tasks, wherein participants made speeded detection responses to peripheral colour targets and then indicated their perceived colours on a colour wheel. In E1, cues were central and endogenous (i.e., prompted voluntary attention) and the interval between cues and targets (stimulus onset asynchrony, or SOA) was always 800 ms. In E2, cues were peripheral and exogenous (i.e., captured attention involuntarily) and the SOA varied between short (100 ms) and long (800 ms). A Bayesian mixed-model analysis was used to isolate the effects of attention on the probability and the fidelity of colour encoding. Both endogenous and short-SOA exogenous spatial cueing improved the probability of encoding the colour of targets. Improved fidelity of encoding was observed in the endogenous but not in the exogenous cueing paradigm. With exogenous cues, inhibition of return (IOR) was observed in both RT and probability at the long SOA. Overall, our findings reinforce the utility of continuous response variables in the research of attention.

4.
J Strength Cond Res ; 33(8): 2053-2056, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30946266

RESUMO

Lawrence, MA, Chin, A, and Swanson, BT. Biomechanical comparison of the reverse hyperextension machine and the hyperextension exercise. J Strength Cond Res 33(8): 2053-2056, 2019-The purpose of this study was to compare activation of the erector spinae, gluteus maximus, and biceps femoris muscles, lower back extension moment, and lower extremity range of motion (ROM) between the reverse hyperextension (RHE) and hyperextension (HE) exercises. Motion and muscle activation of the trunk and lower extremity were measured while 20 recreationally active individuals performed 2 sets of 10 repetitions of each exercise. Equivalent loads were used for each exercise. Peak, average, and integrated muscle activity, low back moment, and ROM between the trunk and pelvis and the thigh and trunk were calculated. A Wilcoxon signed-rank test (p = 0.05) revealed significantly greater integrated activity of the biceps femoris and gluteus maximus during the HE exercise. The RHE exercise generated greater peak (+129%), integrated (+63%), and mean (+78%) low back moment as compared to the HE exercise. The RHE resulted in a significantly greater thigh to trunk ROM, 76.6 compared with 64.7. However, the RHE used less lumbar flexion, 20.4 compared with 31.1 for the HE. The RHE movement profile is preferable because it provides greater hip ROM with less angular stress and equivalent erector spinae activity.


Assuntos
Exercício/fisiologia , Músculo Esquelético/fisiologia , Adulto , Nádegas/fisiologia , Eletromiografia , Feminino , Músculos Isquiotibiais/fisiologia , Humanos , Região Lombossacral/fisiologia , Masculino , Movimento , Músculos Paraespinais/fisiologia , Pelve/fisiologia , Amplitude de Movimento Articular/fisiologia , Coxa da Perna/fisiologia , Adulto Jovem
5.
Psychon Bull Rev ; 26(2): 569-575, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30511232

RESUMO

Studies of exogenous covert orienting use peripheral cues (stimuli) that are spatially uninformative about the locations of subsequent targets. When the time course of the cue's influence on performance is explored (by varying the cue target onset asynchrony; CTOA), a biphasic pattern is usually seen with better performance at the cued location when the CTOA is short (typically attributed to attentional capture) and worse performance at the cued location when the CTOA is long (attributed to inhibition of return). However, while spatially uninformative, these cues (even when a nonaging foreperiod is used) entail a temporal contingency with the subsequent target. Consequently, this so-called capture may reflect an unintended consequence of endogenous allocation of temporal attention. Following Lawrence and Klein (Journal of Experimental Psychology: General, 142(2), 560-572, 2013) we used Rescorla's (Psychological Review, 74, 71-80, 1967) truly random control condition to ensure that the spatially uninformative peripheral stimuli were temporally completely uninformative. Even such completely uninformative peripheral stimuli generated the prototypical biphasic pattern.


Assuntos
Atenção , Sinais (Psicologia) , Orientação Espacial , Adolescente , Feminino , Humanos , Masculino , Tempo de Reação , Incerteza , Adulto Jovem
6.
J Strength Cond Res ; 33 Suppl 1: S45-S51, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30363042

RESUMO

Hecker, KA, Carlson, LA, and Lawrence, MA. Effects of the safety squat bar on trunk and lower-body mechanics during a back squat. J Strength Cond Res 33(7S): S45-S51, 2019-The purpose of this study was to determine whether the safety squat bar (SSB) alters the mechanics and muscle activity of a back squat compared with a standard barbell (ST). Motion and muscle activation of the trunk and lower extremity were measured while 12 competitive powerlifters (8 males, 4 females, age 31.5 ± 6.3 years, body mass 88.1 ± 20.7 kg, competitive lifting experience 3.3 ± 2.8 years) squatted 3 sets of 5 repetitions at 75% of their 3 repetition maximum (3RM). Mean muscle activity and peak joint flexion angles were measured for the trunk and one lower extremity. A repeated-measures analysis of variance (p = 0.05) revealed an 11.3% decrease in 3RM when using the SSB. When using the SSB, there was a decrease in trunk and hip flexion (7.3 and 5.7° respectively) and a 50.3% increase in lower trapezius activation. However, using the SSB decreased activation of the rectus abdominis (46.3%), medial hamstring (17.1%), lateral hamstring (15.1%), vastus lateralis (9.3%), and medial gastrocnemius (18.8%). Squatting with the SSB resulted in a more upright trunk angle, which places less stress on the lower back, a commonly injured area when squatting. Decreases in lower-extremity muscle activation are likely due to the decreased load used, suggesting that the SSB may not be as effective as a standard bar to increase lower-extremity strength. However, the increase in the lower trapezius with the lighter load suggests that midback musculature may be challenged more by the SSB than a standard barbell.


Assuntos
Extremidade Inferior/fisiologia , Músculo Esquelético/fisiologia , Treinamento de Resistência/instrumentação , Tronco/fisiologia , Levantamento de Peso/fisiologia , Adulto , Eletromiografia , Feminino , Músculos Isquiotibiais/fisiologia , Articulação do Quadril/fisiologia , Humanos , Masculino , Músculo Quadríceps/fisiologia , Amplitude de Movimento Articular , Reto do Abdome/fisiologia , Músculos Superficiais do Dorso/fisiologia
7.
J Strength Cond Res ; 33(6): 1648-1652, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28700518

RESUMO

Carlson, LA, Fowler, C, and Lawrence, MA. Agility and vertical jump performances are impacted by acute cool exposure. J Strength Cond Res 33(6): 1649-1653, 2019-Outdoor sports teams may be exposed to acute cold stress during competition, which may affect performance. Limited research has explored the effects of cold exposure on athletic components. The purpose of this study was to examine the effects of an acute whole-body cool exposure on pro-agility, vertical jump, and sprint performances. Eleven lightly clothed (∼0.3 clo) and not cold acclimatized volunteers (10/1 women/men: age 20.5 ± 0.5 years; height 1.65 ± 0.09 m; mass 63.3 ± 8.9 kg; body fat 21.3 ± 7.6%) completed performance tests in both thermoneutral (17.2° C, 36% relative humidity, Biddeford, ME, USA) and cool (6.1° C, 72% relative humidity, Thorsmörk, Iceland) ambient temperatures. Before completing the performance tests, subjects engaged in a 5-minute stretching routine and were subsequently exposed to either a thermoneutral or cool ambient environment for 15 minutes. Performance tests included 3 trials of maximal vertical jumps, and 2 trials of both the 36.6-m sprint and pro-agility tests. Mean performance and lactate values were compared via paired t-tests. Pro-agility completion time was significantly (p ≤ 0.05) slower in the cool (5.63 ± 0.33 seconds) than thermoneutral (5.43 ± 0.26 seconds) environment. Vertical jump was significantly (p ≤ 0.05) lower in the cool (0.36 ± 0.07 m) than thermoneutral (0.41 ± 0.10 m) environment. Sprint performance and lactate values were unaffected by the cool exposure. Brief cool exposure seems to influence agility and vertical jump performances. Our results suggest that it would be prudent for athletes and coaches to consider the ambient environment when preparing for competition.


Assuntos
Desempenho Atlético , Temperatura Baixa , Movimento , Teste de Esforço , Feminino , Humanos , Ácido Láctico/sangue , Masculino , Corrida , Adulto Jovem
8.
Int J Sports Physiol Perform ; 14(3): 351-353, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30160559

RESUMO

BACKGROUND: Sleep deprivation negatively affects cognition, pain, mood, metabolism, and immunity, which can reduce athletic performance. Melatonin facilitates sleepiness and may be affected by the proximity of exercise to sleep. PURPOSE: To evaluate the influence of exercise time of day on salivary melatonin (s-melatonin) responses. METHODS: Twelve regularly exercising men (age 20.75 [0.62] y, height 1.75 [0.04] m, mass 73.63 [10.43] kg, and maximal oxygen consumption 57.72 [6.11] mL/kg/min) participated in a randomized, crossover design. Subjects completed 3 protocols-morning exercise (09:00 h), afternoon exercise (16:00 h), and no exercise (CON)-at least 5 d apart. Exercise sessions consisted of 30 min of steady-state running at 75% of maximal oxygen consumption. Saliva was collected via passive drool at 20:00, 22:00, and 03:00 h following all sessions. RESULTS: Repeated-measures analysis of variance revealed significant time (P = .001) and condition (P = .026) effects for melatonin. Levels of s-melatonin were significantly increased at 03:00 h compared with 20:00 and 22:00 h for all conditions. Post hoc analyses revealed that s-melatonin at 22:00 h was significantly higher after morning exercise (16.5 [7.5] pg/mL) compared with afternoon exercise (13.7 [6.1] pg/mL) sessions (P = .03), whereas neither exercise condition significantly differed from the control (P > .05). CONCLUSIONS: It appears that exercising in the afternoon may blunt melatonin secretion compared with morning exercise. If sleep is an issue, morning exercise may be preferable to afternoon exercise.


Assuntos
Exercício/fisiologia , Melatonina/metabolismo , Saliva/metabolismo , Estudos Cross-Over , Humanos , Masculino , Consumo de Oxigênio , Corrida/fisiologia , Sono/fisiologia , Privação do Sono/fisiopatologia , Fatores de Tempo , Adulto Jovem
9.
Assessment ; : 1073191118818754, 2018 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-30569744

RESUMO

Psychometrically sound tests of intellectual ability are indispensable for research and assessment of children with autism spectrum disorder (ASD), yet few tests have been validated for use with this population. The Merrill-Palmer-Revised Scales of Development (M-P-R) is a standardized test of intellectual ability that was validated for use with typically developing preschoolers. The current study's aim was to investigate the criterion validity of the M-P-R for assessing cognitive skills in preschoolers with ASD ( N = 180). Good concurrent validity was demonstrated, with a large positive correlation between the M-P-R Receptive Language domain and the PLS-4 Auditory Comprehension subscale. The Cognitive domain of the M-P-R showed a medium positive correlation with later WISC-4 scores, showing acceptable predictive validity. Cognitive strengths and weaknesses assessed using the M-P-R mirrored those described for other measures, with most children obtaining higher standard scores on the Cognitive than the Receptive Language domain. An exploratory factor analysis suggested that one factor accounted for the majority of variability in M-P-R domains.

10.
J Strength Cond Res ; 2018 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-30138240

RESUMO

Lawrence, MA, Ostrowski, SJ, Leib, DJ, and Carlson, LA. Effect of unstable loads on stabilizing muscles and bar motion during the bench press. J Strength Cond Res XX(X): 000-000, 2018-Unstable loads are anecdotally used to increase muscle stabilizer strength and utilization; however, there is little evidence to support these claims. Twelve male powerlifters (age 28.6 ± 5.2 years, body mass 105.6 ± 14.5 kg, lifting experience 9.8 ± 6.0 years, and bench press 5 repetition maximum [5RM] 133.6 ± 30.9 kg) pressed their 5RM in one stable condition with a standard barbell, and 3 unstable conditions using a flexible barbell with weights suspended from elastic bands. Mean integrated muscle activity for each repetition of the stabilizers and prime movers were measured. A Lyapunov exponent and sample entropy indicated unstable loads were less predictable and more variable in the superior/inferior direction, thus more challenging to control, despite decreased loads. The main finding was increased bicep activity in all unstable conditions (light bands and plates, +57%; mini bands and plates, +67%; and mini bands and kettlebells, +88%). Although less weight was used in the unstable 5RMs, most stabilizer muscle activity was not different between conditions, suggesting that the amount of weight used during unstable load training (up to 32.3% less load) may be limited by the ability of stabilizer muscles to control the load.

11.
J Strength Cond Res ; 32(7): 2061-2065, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29016483

RESUMO

Carlson, LA, Lawrence, MA, and Kenefick, RW. Hydration status and thermoregulatory responses in drivers during competitive racing. J Strength Cond Res 32(7): 2061-2065, 2018-Stock car drivers are exposed to high ambient temperatures, further complicated by the fact that they are encapsulated in protective clothing; however, the hydration status of these drivers has not been determined. This study quantified the degree of fluid losses during a competitive event in hot conditions. Nine male stock car drivers (29.6 ± 9.4 years, 177.8 ± 3.0 cm, 81.5 ± 18.5 kg) were studied during a Pro Series Division NASCAR race. Sweat rate (SR) and dehydration was determined through nude body weights (BWs). Prerace BW was 81.5 ± 18.5 kg and decreased to 81.1 ± 18.5 kg after race (p = 0.001). Body weight loss after race was 0.77 ± 0.3% and mean SR was 0.63 ± 0.4 L·h. Intestinal core temperature increased from 38.0 ± 0.4 to 38.5 ± 0.4° C after race (p = 0.001). Skin temperature increased from 35.8 ± 0.8 to 36.9 ± 0.8° C after race (p = 0.001), whereas the core-to-skin temperature gradient narrowed from 2.2 ± 0.9 to 1.6 ± 0.9° C, before race to after race (p = 0.001). Heart rates after race were 89 ± 0.0% of the drivers' age-predicted maximum heart rate (HR). Fluid losses during competitive racing can be significant. Without a fluid replacement strategy, fluid losses may exceed 3% of BW and could negatively impact driving performance in longer races.


Assuntos
Condução de Veículo , Regulação da Temperatura Corporal/fisiologia , Esportes/fisiologia , Sudorese/fisiologia , Equilíbrio Hidroeletrolítico/fisiologia , Adulto , Temperatura Corporal/fisiologia , Peso Corporal/fisiologia , Desidratação/fisiopatologia , Frequência Cardíaca/fisiologia , Temperatura Alta/efeitos adversos , Humanos , Masculino
12.
J Strength Cond Res ; 31(5): 1206-1211, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-27548799

RESUMO

Lawrence, MA, Leib, DJ, Ostrowski, SJ, and Carlson, LA. Nonlinear analysis of an unstable bench press bar path and muscle activation. J Strength Cond Res 31(5): 1206-1211, 2017-Unstable resistance exercises are typically performed to improve the ability of stabilizing muscles to maintain joint integrity under a load. The purpose of this study was to examine the effects of an unstable load (as provided by a flexible barbell and a load suspended by elastic bands) on the bar path, the primary musculature, and stabilizing musculature while bench pressing using nonlinear analyses. Fifteen resistance-trained men (age 24.2 ± 2.7 years, mass 84.1 ± 12.0 kg, height 1.77 ± 0.05 m, 9.9 ± 3.4 years of lifting experience, and bench press 1 repetition maximum (RM) 107.5 ± 25.9 kg) volunteered for this study. Subjects pressed 2 sets of 5 repetitions in both stable (total load 75% 1RM) and unstable (total load 60% 1RM) conditions using a standard barbell and a flexible Earthquake bar, respectively. Surface electromyography was used to detect muscle activity of primary movers (pectoralis major, anterior deltoid, and triceps) and bar stabilizing musculature (latissimus dorsi, middle and posterior deltoid, biceps brachii, and upper trapezius). During the unstable condition, the bar moved in more ways and was less predictable in the mediolateral and anteroposterior directions. However, the muscle activation patterns of all muscles were more constrained with the unstable barbell. These findings suggest that the unstable condition was more challenging to control, but subjects controlled the instability by contracting their muscles in a more stable pattern or "staying tight" throughout the exercise.


Assuntos
Exercício/fisiologia , Músculo Esquelético/fisiologia , Levantamento de Peso/fisiologia , Adulto , Músculo Deltoide/fisiologia , Eletromiografia , Humanos , Masculino , Contração Muscular , Força Muscular , Dinâmica não Linear , Músculos Peitorais/fisiologia , Músculos Superficiais do Dorso/fisiologia , Adulto Jovem
13.
J Strength Cond Res ; 31(2): 430-434, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27564994

RESUMO

Ostrowski, SJ, Carlson, LA, and Lawrence, MA. Effect of an unstable load on primary and stabilizing muscles during the bench press. J Strength Cond Res 31(2): 430-434, 2017-Unstable resistance exercises are performed to increase activity of stabilizing muscles. The premise is that this increase in activity will yield greater strength gains than traditional resistance exercises. The purpose of this study was to determine if an unstable load increases muscle activity of stabilizing muscles during a bench press as compared with a standard bench press with a typical load. Fifteen resistance-trained males (age 24.2 ± 2.7 years, mass 84.8 ± 12.0 kg, height 1.77 ± 0.05 m, weight lifting experience 9.9 ± 3.4 years, and bench press 1 repetition maximum [1RM] 107.5 ± 25.9 kg) volunteered for this study. Subjects pressed 2 sets of 5 repetitions in both stable (75% 1RM) and unstable (60% 1RM) conditions using a standard barbell and a flexible Earthquake bar, respectively. Surface electromyography was used to detect muscle activity of primary movers (pectoralis major, anterior deltoid, and triceps) and stabilizing musculature (latissimus dorsi, middle and posterior deltoid, biceps brachii, and upper trapezius). Muscle activity was compared using a multivariate analysis of variance to determine significant (p ≤ 0.05) phase and condition differences. The right and left biceps and the left middle deltoid were significantly more active in the unstable condition. Some of the stabilizing muscles were found to be significantly more active in the unstable condition with 15% less weight. Therefore, bench pressing with an unstable load appears promising in activating stabilizing musculature compared with pressing a typical barbell.


Assuntos
Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Levantamento de Peso/fisiologia , Suporte de Carga/fisiologia , Adulto , Análise de Variância , Peso Corporal , Músculo Deltoide/fisiologia , Eletromiografia , Humanos , Masculino , Músculos Peitorais/fisiologia , Músculos Superficiais do Dorso/fisiologia , Adulto Jovem
14.
J Strength Cond Res ; 31(5): 1236-1240, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-27537409

RESUMO

Carlson, LA, Lawrence, MA, LeCavalier, K, and Koch, AJ. Salivary lymphocyte responses following acute anaerobic exercise in a cool environment. J Strength Cond Res 31(5): 1236-1240, 2017-The purpose of this study was to examine the impact of anaerobic training on salivary lymphocytes (s-LYMPH), and further determine whether these responses differ between cool vs. thermoneutral environments. Nine lightly clothed (∼0.3 clo) volunteers (7/2 women/men: age, 21 ± 1 years; height, 168.7 ± 7.3 cm; weight, 66.4 ± 8.4 kg; body fat, 20.6 ± 7.6%) completed speed, agility, and quickness (SAQ) sessions in both warm (18.9° C; Biddeford) and cool (10.4° C; Thorsmörk) temperatures. The SAQ sessions consisted of 3 trials of 20-m sprints, 40-m sprints, t-tests, and box drills, and two 300-yd shuttle runs in both conditions. Saliva samples via passive drool were collected at baseline, immediately postexercise, and after 2 hours of recovery. The s-LYMPH increased (p < 0.001) immediately postexercise, followed by a decrease (p < 0.001) below baseline values after 2 hours of recovery in both environments. The s-LYMPH counts were lower (p < 0.001) for the cool environment than for the thermoneutral environment. The s-LYMPH counts increased postexercise, followed by a decrease after 2 hours of recovery regardless of environment. Acute anaerobic exercise induced transient changes in s-LYMPH counts similar to that observed in peripheral blood. Compared with baseline measures, changes in s-LYMPH were of a smaller magnitude after exercise in the cool environment compared with thermoneutral environment. In summary, there is no indication that exercise in the cool environment presented a greater challenge to the subjects' immunity. Rather, these data indicate exercise in a cool environment produces smaller fluctuations in salivary immune cells compared with resting levels.


Assuntos
Limiar Anaeróbio/fisiologia , Linfócitos , Corrida/fisiologia , Saliva/citologia , Temperatura Ambiente , Teste de Esforço , Feminino , Humanos , Contagem de Linfócitos , Masculino , Adulto Jovem
15.
J Exp Psychol Gen ; 145(1): 56-81, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26709589

RESUMO

We investigated whether intentional forgetting impacts only the likelihood of later retrieval from long-term memory or whether it also impacts the fidelity of those representations that are successfully retrieved. We accomplished this by combining an item-method directed forgetting task with a testing procedure and modeling approach inspired by the delayed-estimation paradigm used in the study of visual short-term memory (STM). Abstract or concrete colored images were each followed by a remember (R) or forget (F) instruction and sometimes by a visual probe requiring a speeded detection response (E1-E3). Memory was tested using an old-new (E1-E2) or remember-know-no (E3) recognition task followed by a continuous color judgment task (E2-E3); a final experiment included only the color judgment task (E4). Replicating the existing literature, more "old" or "remember" responses were made to R than F items and RTs to postinstruction visual probes were longer following F than R instructions. Color judgments were more accurate for successfully recognized or recollected R than F items (E2-E3); a mixture model confirmed a decrease to both the probability of retrieving the F items as well as the fidelity of the representation of those F items that were retrieved (E4). We conclude that intentional forgetting is an effortful process that not only reduces the likelihood of successfully encoding an item for later retrieval, but also produces an impoverished memory trace even when those items are retrieved; these findings draw a parallel between the control of memory representations within working and long-term memory.


Assuntos
Atenção , Intenção , Reconhecimento Visual de Modelos , Probabilidade , Repressão Psicológica , Feminino , Humanos , Julgamento , Funções Verossimilhança , Masculino , Rememoração Mental , Tempo de Reação , Adulto Jovem
16.
Child Neuropsychol ; 22(2): 155-76, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-25413609

RESUMO

A sex-balanced sample (N = 96) of children from age 6.5 to age 12.5 completed a modified Attention Network Test. Across these ages, we found evidence for developmental changes to alerting and executive control but stable orienting. Additionally, we found that the youngest members of our sample manifested an interaction between alerting and executive control that is opposite to that typically found in adults; a reversal that diminishes with age to achieve the adult pattern by the older end of the age range of our sample.


Assuntos
Atenção , Conscientização/fisiologia , Desenvolvimento Infantil , Função Executiva/fisiologia , Orientação/fisiologia , Criança , Sinais (Psicologia) , Feminino , Humanos , Masculino , Fatores Socioeconômicos
17.
J Strength Cond Res ; 29(11): 3075-8, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26506061

RESUMO

Noncontact anterior cruciate ligament (ACL) injuries often occur during lateral cutting maneuvers, in which extension, adduction, and external rotation create high loads on the ACL. The aim of this study was to examine knee moments and foot strike patterns during lateral cutting when shod (SD) and barefoot (BF). Fifteen NCAA Division III athletes (7 female and 8 male; age 20.2 ± 1.5 years; mass 71.5 ± 11.3 kg; height, 1.7 ± 0.06 m) without lower limb pathologies were analyzed during 5 trials of 45° lateral cutting maneuvers for each limb in both BF and SD conditions with the approach speed of 4.3 m·s. Kinetic and kinematic data were collected using an 8-camera motion capture system and a force plate with collection rates at 240 Hz and 2400 Hz, respectively. Paired t-tests were used to determine differences conditions. The SD condition produced a significantly (p ≤ 0.05) greater peak adduction moment and cutting, whereas BF caused more anterior foot strike. Lateral cutting when BF places no more stress on the ACL than when SD. Our findings suggest that lateral cutting maneuvers when BF will not increase stress on the ACL.


Assuntos
Articulação do Joelho/fisiologia , Sapatos , Futebol/fisiologia , Lesões do Ligamento Cruzado Anterior , Fenômenos Biomecânicos/fisiologia , Feminino , Humanos , Masculino , Movimento/fisiologia , Adulto Jovem
18.
J Strength Cond Res ; 29(10): 2949-53, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25844869

RESUMO

Stability training has become commonplace in the strength and conditioning field. Although unstable surface training has been investigated, little is known regarding the efficacy of performing resistance exercises with an unstable load. The purpose of this study was to determine if performing a parallel back squat with an unstable load (weights suspended from the bar by an elastic band) produces greater ground reaction forces (GRFs) and muscle activation in the trunk and lower extremities than a stable condition (a normally loaded barbell). Fifteen resistance-trained males (age: 24.2 ± 3.4 years, mass: 83.4 ± 18.7 kg) completed 10 repetitions of the back squat, with 60% of their 1 repetition maximum in both stable and unstable conditions. Peak vertical GRF and the integrated muscle activity of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, soleus, rectus abdominis, external oblique, and erector spinae muscles on the right side of the body were determined The unstable load resulted in a small (3.9%) but significant decrease in peak vertical GRF. The unstable load also produced greater muscle activation in the rectus abdominis, external oblique, and soleus. The findings of this study suggest that squatting with an unstable load will increase activation of the stabilizing musculature; and while force decrements were statistically significant, the decrease was so small it may not be relevant to practitioners.


Assuntos
Extremidade Inferior/fisiologia , Músculo Esquelético/fisiologia , Treinamento de Resistência/métodos , Eletromiografia , Humanos , Masculino , Tronco/fisiologia , Adulto Jovem
19.
J Abnorm Child Psychol ; 43(3): 567-75, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25117578

RESUMO

Research on the expression of positive affect in young children with Autism Spectrum Disorder (ASD) suggests that differences in this domain emerge late in the first year or early in the second year. However, many previous studies in this area employed retrospective research methods and global rating schemes. In the current study, the expression of positive affect was examined prospectively at ages 6, 12, and 18 months in three groups: infant siblings with ASD, infant siblings without ASD, and low-risk comparison infants. Infant siblings were the younger brothers or sisters of children diagnosed with ASD and, therefore, had a higher familial risk of ASD. The frequency and duration of smiles were coded from video excerpts from the Autism Observation Scale for Infants (Bryson, Zwaigenbaum, McDermott, Rombough, and Brian 2008), a standardized, play-based assessment of early signs of ASD. Results indicated that at 12 months, infant siblings with ASD had a lower rate of smiling than the other two groups. At 18 months, infant siblings with ASD continued to display a lower rate of smiling than infant siblings without ASD, but not comparison infants. Overall, these results indicate that infant siblings with ASD demonstrate less positive affect than infant siblings without ASD and low-risk comparison infants at 12 months. This suggests that reduced smiling may be an informative behavioural risk marker for ASD by children's first birthdays and may have implications for our understanding of atypical social development in children with ASD.


Assuntos
Transtorno do Espectro Autista/diagnóstico , Irmãos/psicologia , Sorriso , Estudos de Casos e Controles , Feminino , Humanos , Lactente , Estudos Longitudinais , Masculino , Jogos e Brinquedos , Estudos Prospectivos
20.
J Strength Cond Res ; 28(5): 1241-5, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24513621

RESUMO

Sled towing is a popular method of sprint training. Researchers have struggled to identify a loading scheme that is most appropriate to improve sprint performance in the acceleration phase. The purpose of this study was to determine if loads of 10% body weight (BWT) or 20% BWT produced significantly greater propulsive ground reaction force (GRF) impulse, peak propulsive GRF, or a greater propulsive rate of force development (RFD) than an unweighted sprint start. Seventeen healthy court and field athletes (10 men, 7 women; 20.9 ± 1.1 years) completed 5 starts of each condition (unweighted, 10% BWT, 20% BWT). Participants began each start in an upright staggered stance. Propulsive GRF impulse was greater in the 20% BWT condition than the unweighted condition in both limbs and greater in the 20% BWT condition than the 10% BWT condition in the front leg only, and vertical GRF impulse was greater in the 20% BWT than the unweighted condition. In summary, our results suggest that a 10% BWT load is not sufficient to increase propulsive GRF impulse. A loading scheme of 20% BWT is sufficient to increase propulsive GRF impulse. Coaches seeking to improve sprint starts may observe improvements using a load of 20% BWT during training while towing a sled.


Assuntos
Desempenho Atlético/fisiologia , Condicionamento Físico Humano/métodos , Corrida/fisiologia , Aceleração , Peso Corporal , Feminino , Humanos , Masculino , Adulto Jovem
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