Sex differences in the impact of state and trait fatigue on gait variability

Conditions requiring greater attention or cognitive control, such as fatigue, lead to changes in the motor performance of a task. Perceived fatigue refers to subjective feelings of fatigue, can be expressed as a state variable or trait characteristic and is influenced by demographic factors, such as sex. The purpose of this study was to determine how sex interacts with state and trait physical fatigue (PF) and mental fatigue (MF) to influence gait variability. METHODS: 123 healthy adults (77 female, 46 male), aged 18–36 years, completed the Mental and Physical State and Trait Energy and Fatigue Scale. Using a median split for each fatigue variable, participants were placed into “low” or “high” fatigue categories. Gait variability was defined as the asymmetry of lateral step variability (ALSV) and coefficient of variation (CV) of gait speed, stride length and double limb (DL) support during overground walking. RESULTS: Males with low state PF had greater ALSV than females with low state PF (p = 0.05, η²_p = 0.07) and males with high state PF (p = 0.007, η²_p = 0.15). Females with high trait MF had greater CV of gait speed than females with low trait mental fatigue (p = 0.02, η²_p = 0.08). Males with low trait MF had greater CV of gait speed (p = 0.01, η²_p = 0.10) and stride length (p = 0.002, η²_p = 0.17) than females with low trait MF. CV of DL support did not vary based on fatigue level or sex (p ≥ 0.11). CONCLUSIONS: There are sex-specific differences in the impact of state PF on asymmetry of lateral step variability and trait MF on the variability of gait speed and stride length.     

Slipping during side-step cutting: Anticipatory effects and familiarization

The aim of the present study was to verify whether the expectation of perturbations while performing side-step cutting manoeuvres influences lower limb EMG activity, heel kinematics and ground reaction forces. Eighteen healthy men performed two sets of 90° side-step cutting manoeuvres. In the first set, 10 unperturbed trials (Base) were performed while stepping over a moveable force platform. In the second set, subjects were informed about the random possibility of perturbations to balance throughout 32 trials, of which eight were perturbed (Pert, 10 cm translation triggered at initial contact), and the others were “catch” trials (Catch). Center of mass velocity (CoM_VEL), heel acceleration (H_AC), ground reaction forces (GRF) and surface electromyography (EMG) from lower limb and trunk muscles were recorded for each trial. Surface EMG was analyzed prior to initial contact (PRE), during load acceptance (LA) and propulsion (PRP) periods of the stance phase. In addition, hamstrings-quadriceps co-contraction ratios (CCR) were calculated for these time-windows. The results showed no changes in CoM_VEL, H_AC, peak GRF and surface EMG PRE among conditions. However, during LA, there were increases in tibialis anterior EMG (30–50%) concomitant to reduced EMG for quadriceps muscles, gluteus and rectus abdominis for Catch and Pert conditions (15–40%). In addition, quadriceps EMG was still reduced during PRP (p < .05). Consequently, CCR was greater for Catch and Pert in comparison to Base (p < .05). These results suggest that there is modulation of muscle activity towards anticipating potential instability in the lower limb joints and assure safety to complete the task.     

Smaller muscle mass is associated with increase in EMG–EMG coherence of the leg muscle during unipedal stance in elderly adults

Age-induced decline in the ability to perform daily activities is associated with a deterioration of physical parameters. Changes occur in neuromuscular system with age; however, the relationship between these changes and physical parameters has not been fully elucidated. Therefore, in this study, we aimed to determine the relationship between neuromuscular system evaluated using a coherence analysis of the leg muscles and physical parameters in community-dwelling healthy elderly adults. The participants were required to stand still in bipedal and unipedal stances on a force plate. Then, electromyography (EMG) was recorded from the tibialis anterior (TA) and medial and lateral gastrocnemius (MG/LG) muscles, and intermuscular coherence was calculated between the following pairs: TA and MG (TA–MG), TA and LG (TA–LG), and MG and LG (MG–LG). Furthermore, gait speed, unipedal stance time, and muscle mass were measured. EMG–EMG coherence for the MG–LG pair was significantly greater in the unipedal stance task than in the bipedal one (p = .001). Multiple linear regression analysis revealed that the muscle mass of the leg was negatively correlated with the change in the β-band coherence for the MG–LG pair from bipedal to unipedal stance (R² = 0.067, standard β = −0.345, p = .044). As the β-band coherence could reflect the corticospinal activity, the increased β-band coherence may be a compensation for the smaller muscle mass, or alternatively may be a sign of changes in the nervous system resulting in the loss of muscle mass.     

The effects of lemon taste on attention,perceived exertion,and affect during a stepping task

ObjectivesTo better understand the effects of taste cues on delaying the attention shift from an external focus (dissociative) towards an internal focus (associative) as exercise intensity increases.DesignA between subjects' experimental design with random assignment to three groups: taste (lemon-flavored mouth guards), placebo (unflavored mouth guards), or control group (no mouth guards) was used. Participants reported perceived exertion, affect (i.e., pleasantness and arousal), and attention allocation before, during, and after performing a weighted stepping task.ResultsPerforming the task resulted in a gradual increase of perceived exertion, F (1.87, 74.89) = 63.05, p < .05, η_p² = .61, along with a shift from dissociative to associative attention, F (2.17, 86.68) = 35.57, p < .05, η_p² = .47 across all conditions. Additionally, participants reported feeling less pleasant and more aroused after task completion in all conditions. The lemon-flavored mouth guard failed to affect attention, F (4.33, 86.68) = 1.41, p = .23, η_p² = .07, perceived exertion, F (3.74, 74.86) = .38, p = .81, η_p² = .02, pleasantness, F (2, 40) = .126, p = .88, η_p² = .01, and arousal, F (2, 40) = 2.40, p = .10, η_p² = .10, differently than the other two conditions.ConclusionsThe study was one of the first to examine the effects of taste during an exertive task. Despite the non-significant effects of using a lemon-taste mouth guard on various cognitive variables (perception of exertion, attention allocation, pleasantness, and arousal), more scientific effort is needed to explore the effects of other tastes (e.g., sweet, bitter) and delivery methods (e.g., sprays, drops).     

Anticipatory and compensatory postural adjustments in sitting in children with cerebral palsy

The aim of this study was to examine postural control in children with cerebral palsy performing a bilateral shoulder flexion to grasp a ball from a sitting posture. The participants were 12 typically developing children (control) without cerebral palsy and 12 children with cerebral palsy (CP). We analyzed the effect of ball mass (1 kg and 0.18 kg), postural adjustment (anticipatory, APA, and compensatory, CPA), and groups (control and CP) on the electrical activity of shoulder and trunk muscles with surface electromyography (EMG). Greater mean iEMG was seen in CPA, with heavy ball, and for posterior trunk muscles (p < .05). The children with CP presented the highest EMG and level of co-activation (p < .05). Linear regression indicated a positive relationship between EMG and aging for the control group, whereas that relationship was negative for participants with CP. We suggest that the main postural control strategy in children is based on corrections after the beginning of the movement. The linear relationship between EMG and aging suggests that postural control development is affected by central nervous disease which may lead to an increase in muscle co-activation.     

Acute exercise and children’s cognitive functioning: What is the optimal dose of cognitive challenge?

Acute bouts of exercise have the potential to benefit children’s cognition. Inconsistent evidence on the role of qualitative exercise task characteristics calls for further investigation of the cognitive challenge level in exercise. Thus, the study aim was to investigate which “dose” of cognitive challenge in acute exercise benefits children’s cognition, also exploring the moderating role of individual characteristics. In a within-subject experimental design, 103 children (M_age = 11.1, SD = 0.9, 48% female) participated weekly in one of three 15-min exergames followed by an Attention Network task. Exergame sessions were designed to keep physical intensity constant (65% HR_max) and to have different cognitive challenge levels (low, mid, high; adapted to the ongoing individual performance). ANOVAs performed on variables that reflect the individual functioning of attention networks revealed a significant effect of cognitive challenge on executive control efficiency (reaction time performances; p = .014, ƞ²_p = .08), with better performances after the high-challenge condition compared to lower ones (ps < .015), whereas alerting and orienting were unaffected by cognitive challenge (ps > .05). ANOVAs performed on variables that reflect the interactive functioning of attention networks revealed that biological sex moderated cognitive challenge effects. For males only, the cognitive challenge level influenced the interactive functioning of executive control and orienting networks (p = .004; ƞ²_p = .07). Results suggest that an individualized and adaptive cognitively high-challenging bout of exercise is more beneficial to children’s executive control than less challenging ones. For males, the cognitive challenge in an acute bout seems beneficial to maintain executive control efficiency also when spatial attention resources cannot be validly allocated in advance. Results are interpreted referring to the cognitive stimulation hypothesis and arousal theory.     

The Daily Mile™: Acute effects on children’s cognitive function and factors affecting their enjoyment

The Daily Mile™ is a widely implemented school-based physical activity initiative. However, only two studies have explored the acute effects of participation in The Daily Mile on children’s cognitive functioning, reporting conflicting findings. Moreover, enjoyment of exercise is a determining factor in children’s motivation for, and adherence to, initiatives. However, factors affecting children’s enjoyment of The Daily Mile are unknown. Therefore, this study examined the acute effects of The Daily Mile on cognition and explored children’s enjoyment of participation in the initiative. Following familiarisation, 104 children (10.4 ± 0.7 years) completed a Daily Mile and resting control trial in a randomised, counterbalanced order. Prior to, immediately following and 45 min following The Daily Mile and resting, children completed the Stroop test (inhibitory control), Sternberg paradigm (visual working memory) and Flanker task (inhibitory control and cognitive flexibility). Additionally, 87 children took part in focus groups to explore factors affecting enjoyment. Cognitive data were analysed using two-way (trial*time) and three-way (trial*time*sex; trial*time*fitness) repeated measures analysis of variance (ANOVA). Focus group data were analysed using qualitative content analysis. There were no statistically significant effects of The Daily Mile on cognition, compared to rest (all p > 0.05). However, accuracy on the one-item level of Sternberg paradigm (p = 0.073, η_p² = 0.028) and complex level of the Stroop test (p = 0.057; η_p² = 0.031) tended to improve immediately following The Daily Mile, compared to resting; though this did not reach statistical significance. Children enjoyed participating in The Daily Mile, particularly due to its outdoor location, social context, and self-paced nature. However, some children found The Daily Mile boring due to its repetitive nature. Findings suggest that The Daily Mile does not significantly influence children’s immediate or delayed (45 min) cognition. However, there was a tendency for improved accuracy in visual working memory and inhibitory control immediately following The Daily Mile. Moreover, the findings demonstrate that The Daily Mile promotes enjoyment, particularly through social relatedness and autonomy. However, future research could consider whether adding variety into the initiative may help to sustain engagement in the children experiencing boredom.     

Comparison of trunk muscle reflex activation patterns between active and passive trunk flexion–extension loading conditions

The aim of the present study was to determine the effects of trunk flexion–extension loading on the neuromuscular reflexive latencies and amplitude responses of the trunk musculature. Eighteen male and female subjects (18–27 yrs) participated in active and passive trunk flexion extension, performed ∼7 days apart. Subjects performed 60 trunk flexion–extension repetitions. Surface electromyography (EMG) was collected bilaterally from paraspinal and abdominal muscles. In the active condition, subjects volitionally moved their trunks, while in the passive condition the dynamometer controlled the movements. The trunk was perturbed before and immediately after 30 repetitions. Latency of muscle onset, latency of first peak, latency of maximum peak, and peak EMG amplitude were evaluated. No differences between conditions, sides, or perturbation session were apparent. Overall latencies were shorter in females (p < .05) and abdominal muscles compared to paraspinals (p < .05). Thoracic paraspinal muscle amplitudes were greater than all other muscles (p < .05). Based upon the present results, the neuromuscular system engages trunk flexor muscles prior to the paraspinals in order to provide possible stabilization of the trunk when flexor moments are generated. Overall, the results indicate no difference in response of the neuromuscular system to active or passive repetitive loading.     

The effects of autonomous difficulty selection on engagement,motivation, and learning in a motion-controlled video game task

This experiment investigated the relationship between motivation, engagement, and learning in a video game task. Previous studies have shown increased autonomy during practice leads to superior retention of motor skills, but it is not clear why this benefit occurs. Some studies suggest this benefit arises from increased motivation during practice; others suggest the benefit arises from better information processing. Sixty novice participants were randomly assigned to a self-controlled group, who chose the progression of difficulty during practice, or to a yoked group, who experienced the same difficulty progression but did not have choice. At the end of practice, participants completed surveys measuring intrinsic motivation and engagement. One week later, participants returned for a series of retention tests at three different difficulty levels. RM-ANCOVA (controlling for pre-test) showed that the self-controlled group had improved retention compared to the yoked group, on average, β = 46.78, 95% CI = [2.68, 90.87], p = 0.04, but this difference was only statistically significant on the moderate difficulty post-test (p = 0.004). The self-controlled group also showed greater intrinsic motivation during practice, t(58) = 2.61, p = 0.01. However, there was no evidence that individual differences in engagement (p = 0.20) or motivation (p = 0.87) were associated with learning, which was the relationship this experiment was powered to detect. These data are inconsistent with strictly motivational accounts of how autonomy benefits learning, instead suggesting the benefits of autonomy may be mediated through other mechanisms. For instance, within the information processing framework, the learning benefits may emerge from learners appropriately adjusting difficulty to maintain an appropriate level of challenge (i.e., maintaining the relationship between task demands and cognitive resources).     

Effect of psychostimulant medications on static balance performance in adults with attention deficit hyperactivity disorder: Within-subjects repeated-measure study

ObjectiveThis study examined the effect of psychostimulant medications nPS) on balance and functional motor performance in adults with attention-deficit/hyperactivity disorder (ADHD).MethodsParticipants completed two sessions (off-medication and on-medication) in a within-subjects repeated-measure study design. There was a minimum of seven days between the two sessions. During both sessions, participants stood for 30 s per condition on a force platform. The conditions were: feet-apart with 1) eyes-open and 2) eyes-closed; feet-together with 3) eyes-open and 4) eyes-closed. Participants performed three trials of timed up and go (TUG) and lateral step-up test (LSUT) during both sessions. Outcome measures were sway area (SA [cm²]), average sway velocity (SV [cm/s]), TUG average time (s), and average number of LSUT repetitions. Data were analyzed using multivariate repeated measures analysis of variance and paired t-tests for examining PS effects on balance (SA and SV) and functional motor performance (TUG and LSUT), respectively.ResultsThe sample included 45 adults (35 females; mean age = 28.4 ± 6.3 years). The repeated-measures MANOVA indicated that PS was associated with better SA [F(1,44) = 9.6; p = 0.003;η_p² = 0.18] but not with SV [F(1,44) = 1.0; p = 0.319;η_p² = 0.02]. PS was associated with significantly better SA with decreasing base-of-support [F(1,44) = 9.9; p = 0.003;η_p² = 0.18]. Additionally, PS use was associated with better TUG [t(1,44) = 2.65; p = 0.014;Cohen's d = 0.39] but not LSUT performances [t(1,44) = −0.68; p = 0.499;Cohen's d = −0.10].ConclusionsPS was associated with better SA and TUG in adults with ADHD. Further studies are needed to investigate the effects of PS on balance performance using rigorous designs in this population.ImpactHealthcare providers should screen for PS status and balance when treating adults with ADHD to enhance safe motor performance.     

The predictive relationships between advanced dynamic balance and physical activity/quality of life in Parkinson's disease

Gait and balance problems commonly occur in Parkinson's disease (PD). However, balance tasks with only one performance objective (e.g., sit-to-stand) may not be sufficient, compared to dual motor tasks (e.g., carrying a tray while walking), to be applied to the assessments and interventions which are designed to promote PD patients' balance functioning, physical activity (PA) and health-related quality of life (HQoL). The aim of this study, therefore, was to determine whether advanced dynamic balance, measured by a demanding motor-motor dual task, is a significant predictor of PA/HQoL in older adults with and without PD. Participants with (n = 22) and without (n = 23) PD were assessed using the Berg Balance Scale (BBS), the single leg hop and stick series task (SLHS), the Physical Activity Scale for the Elderly (PASE), and the Parkinson's Disease Questionnaire–39 (PDQ39). We calculated the R² change, namely the incremental validity, between the multiple regression models before and after adding the scores on the BBS/SLHS. While controlling for biological and socioeconomic covariates, competence in the SLHS task provided moderate and large levels of incremental validity to PA (ΔR² = 0.08, Cohen's f² = 0.25, p = .035) and HQoL (ΔR² = 0.13, Cohen's f² = 0.65, p < .001), respectively. In particular for participants with PD, the SLHS explained significantly more variance in HQoL in relation to psychosocial functioning (ΔR² = 0.25, Cohen's f² = 0.42, p = .028) compared to the BBS (p = .296). Assessing advanced dynamic balance by means of a highly demanding dual-task paradigm was not only strongly associated with PA but also covered a wider spectrum of HQoL components. This approach is recommended for use in evaluations and interventions carried out in clinical and research settings in order to promote healthy living.     

Boredom,motivation, and perceptions of pain: Mechanisms to explain the effects of self-control exertion on subsequent physical performance

ObjectivesPrior self-control exertion has been shown to have a detrimental effect on subsequent physical performance. However, some potential underpinning mechanisms of the effect have yet to be examined. The present study explored whether exerting self-control reduces subsequent physical performance; and also examines the role of boredom, motivation, perceptions of pain, and sustained attention as mechanisms to explain these performance effects.MethodsIn a within-subjects order-balanced crossover design, 63 participants completed a self-control exertion task (incongruent Stroop) and non-self-control exertion task (congruent Stroop) for 4 min. Immediately after, participants completed a wall-sit task until volitional exhaustion. Task-specific boredom was measured following the Stroop task and following the wall-sit task. Participants’ perceptions of pain and motivation were measured every 30 s during the wall sit task. Upon completion of the wall-sit, participants completed a test of sustained attention.ResultsFollowing the self-control exertion task, participant’s wall-sit performance time was reduced (136 ± 62 s), compared to when they completed the non-self-control exertion task (144 ± 57 s, p = 0.05, d = 0.14). Participant’s task related boredom was significantly higher during the non-self-control exertion task (4.30 ± 1.23), compared to the self-control exertion task (3.82 ± 1.22) (p < 0.001, d = 0.39); but boredom was not different during the wall-sit task (p = 0.79). Prior self-control exertion also led to increased overall perceptions of pain (p = 0.02) and reduced overall (p = 0.01) and initial (p = 0.02) motivation during the wall-sit task. However, no differences in initial perceptions of pain (p = 0.16) or sustained attention (response time, p = 0.99; response accuracy, p = 0.78) were observed. Additional within-subjects mediation analysis revealed that differences in wall-sit performance time could not be explained by differences in task related boredom during the Stroop task, overall perceptions of pain, or overall and initial motivation (all p > 0.05).ConclusionsThe prior exertion of self-control resulted in a decrement in subsequent physical performance. Furthermore, individuals’ perceptions of task related boredom were higher during the non-self-control exertion (congruent Stroop) task, whilst overall perceptions of pain were higher, and initial and overall motivation were lower, following the self-control exertion (incongruent Stroop) task. However, mediation analysis revealed that these mechanisms did not explain the difference in wall sit performance time between the conditions.     

Approach-achievement goals and motivational context on psycho-physiological functioning and performance among novice basketball players

ObjectivesDrawing from an integrated motivational model (Vansteenkiste, Lens, Elliot, Soenens, & Mouratidis, 2014), this study tested the impact of induced approach-based achievement goal states under different motivational contexts on the psycho-physiological functioning and motor task performance of novice basketball players.DesignA 3 × 2 (Goal [task-/self-/other-approach] x Context [autonomy-supportive/controlling]) repeated measures experimental design was employed.Method114 novice participants (M_age = 23.53; SD = 4.56) performed a basketball shooting task. They were subsequently randomly assigned to one of six experimental conditions before repeating this task. Physiological (heart rate [HR] and blood pressure [BP]) and psychological (stress appraisals, state anxiety, task enjoyment, perceived competence, and goal attainment) data were captured at different intervals throughout the experiment.ResultsFactorial ANOVAs revealed participants: 1) performing under a controlling motivational context reported significantly higher HR (p < .001) and systolic BP (p < .05) post-task compared to those operating within an autonomy-supportive environment, 2) induced to an other-approach goal group, recorded significantly higher diastolic BP (p < .05) than those induced to self- and task-approach goals post-task, 3) adopting a task-approach goal under controlling conditions appraised the shooting task as significantly more threatening (p < .05) than their counterparts in the task-approach autonomy-supportive condition, and finally, 4) following approach-based goals under an autonomy-supportive context significantly improved their performance (p < .001) from pre-to post-shooting task.ConclusionsOur findings provide limited support for an integrated motivational model and are discussed in relation to their unique theoretical and practical utility.     

Predicting changes in planning behaviour and physical activity among adults

Though the effect of action planning upon behavioural enactment is becoming well-established, adherence to planning interventions are modest. Motivations specific to action planning may predict planning behaviour. The primary purpose of the present study was to determine if theory of planned behaviour constructs operationalized for planning could predict change in planning behaviour. The secondary purpose was to determine if planning behaviour predicted changes in physical activity. Participants (n = 337, M_age = 31 ± 5) were adults with intentions to be more active who completed measures of affective and instrumental attitudes towards planning, subjective norms towards planning, perceived behavioural control over planning, intentions to plan, self-reported planning behaviour, intentions to be active and self-reported physical activity at baseline (T1) and after four weeks (T2). Affective attitudes towards planning (β = 0.10, p < .05), instrumental attitudes towards planning (β = 0.22; p < .01) subjective norms over planning (β = 0.12, p < .01) and perceived behavioural control over planning (β = 0.53, p < .01) predicted intentions to plan (adj. R² = 0.66). Intentions to plan (β = 0.16, p < .05) and intentions to be active (β = −0.25, p < .05) predicted change in planning behaviour (R²_change = 0.03). Planning behaviour (β = 0.27, p < .05) predicted change in physical activity (R²_change = 0.07). Planning behaviour appears to have its own motivations distinct from those of physical activity. Future interventions should target planning behaviour along with its motivations and control beliefs to increase rates of planning. The theoretical underpinnings of the TPB are of value for understanding both planning behaviour and physical activity.     

Local muscle oxygen consumption related to external and joint specific power

The purpose of the present study was to examine the effects of external work rate on joint specific power and the relationship between knee extension power and vastus lateralis muscle oxygen consumption (mVO₂). We measured kinematics and pedal forces and used inverse dynamics to calculate joint power for the hip, knee and ankle joints during an incremental cycling protocol performed by 21 recreational cyclists. Vastus lateralis mVO₂ was estimated using near-infrared spectroscopy with an arterial occlusion. The main finding was a non-linear relationship between vastus lateralis mVO₂ and external work rate that was characterised by an increase followed by a tendency for a levelling off (R² = 0.99 and 0.94 for the quadratic and linear models respectively, p < 0.05). When comparing 100 W and 225 W, there was a ∼43 W increase in knee extension but still a ∼9% decrease in relative contribution of knee extension to external work rate resulting from a ∼47 W increase in hip extension. When vastus lateralis mVO₂ was related to knee extension power, the relationship was still non-linear (R² = 0.99 and 0.97 for the quadratic and linear models respectively, p < 0.05). These results demonstrate a non-linear response in mVO₂ relative to a change in external work rate. Relating vastus lateralis mVO₂ to knee extension power showed a better fit to a linear equation compared to external work rate, but it is not a straight line.     

Using error-estimation to probe the psychological processes underlying contextual interference effects

Although the learning benefits of interleaved practice schedules relative to blocked schedules are well-reported, the mechanisms underlying these effects are not fully understood. Researchers have generally suggested that random schedules of practice increase task-related information processing which arises due to switching between variations of the same task (or switching between different tasks). Thus, one potentially useful way to both probe and manipulate contextual interference is to pair it with error estimation during practice. Forced error estimation increases task-related information processing and recording these estimates provides insight into learners' self-awareness of their errors. In the present study, 84 participants were randomly allocated to four groups. Participants practiced a timing task under blocked or random schedules, with and without error estimations prior to feedback. During the acquisition phase, three target times were trained (1500, 1700, 1900 ms), with feedback delivered after every trial. We used delayed post-tests (24 hrs later) to evaluate the retention of these target times and their transfer to two new target times (1600, 1800 ms). Participants who practiced with a random schedule performed worse (i.e., greater absolute error) than those with a blocked schedule during acquisition (p = .006); however, randomly scheduled participants also showed reduced error (p = .004) on the retention and transfer tests. Although prompting error estimations led to greater self-reported mental effort being invested on the task (p = .001), error estimation was not reliably associated with superior learning (p = .133). The accuracy of error estimations did not differ as a function of practice structure (p = .070), although the accuracy of error estimations improved during acquisition (p = .006). Findings highlight the robustness of the contextual interference effect, but we did not find evidence that error estimations moderated the effect on this task. It is in some ways surprising that we found an effect of contextual interference, as past-work suggests that interference effects are attenuated (or eliminated) when participants switch between different parameters of the same task. We speculate that this might be due to the difficulty of the task; even though participants switched between parametric variations of the same task, the distinction between parameters was subtle (i.e., tenths of a second).     

Psychological need satisfaction and thwarting: A test of Basic Psychological Needs Theory in physical activity contexts

ObjectivesTo test Basic Psychological Needs Theory (BPNT; Deci & Ryan, 2002) to determine if psychological need thwarting experienced when physically active contributes to the understanding of well-being and ill-being.Design/methodParticipants (N = 155, 67.70% female, M_age = 37.46 years; SD_age = 19.89 years) completed assessments of psychological need satisfaction and thwarting, subjective vitality and positive/negative affect during separate testing sessions separated by 6 months.ResultsScores from the modified version of the Psychological Need Thwarting Scale (PNTS-PA; Bartholomew, Ntoumanis, Ryan, & Thøgersen-Ntoumani, 2011) demonstrated discriminant evidence of validity, evidence of internal structure and minimal error variance. Changes in psychological need satisfaction positively predicted positive affect (R² = .16, p < .05), subjective vitality (R² = .13, p < .05) and negatively predicted negative affect (R² = .12, p < .05). Additional regression analyses revealed that changes in psychological need thwarting predicted negative affect (ΔR² = .11, p < .05), but not positive affect (ΔR² = .01, p > .05) or subjective vitality (ΔR² = .04, p > .05) beyond contributions made by psychological need satisfaction.ConclusionsOverall, these results extend the potential utility of the PNTS-PA as an instrument for use with BPNT beyond sport and support Deci and Ryan's (2002) contentions regarding the critical role of psychological need thwarting.     

Motor imagery combined with action observation training optimized for individual motor skills further improves motor skills close to a plateau

The acquisition of high-level motor skills beyond a “plateau” is important in sports training and rehabilitation. We aimed to investigate whether motor skills close to a plateau state can be improved further by performing motor imagery (MI) training while observing movements with difficulty levels optimized for individual motor skills. The subjects were divided randomly into four groups (n = 10 per group): the control group and three groups of MI combined with action observation (MI + AO) training with varying difficulty levels. The task was to rotate the two cork balls 20 times counterclockwise using the left hand. The subjects performed 30 and 10 successful trials of this task before and after MI + AO training, respectively. In the three training groups, MI training was performed while observing videos showing ball rotation movements adjusted to the same level, a moderately higher level, or a remarkably higher level of difficulty than that achieved by the individual subjects. The improvement rate of the ball rotation time after MI + AO training was significantly higher in the moderate-difficulty than in the control group and remarkably higher level of difficulty group. The other two MI + AO training groups did not differ significantly compared with the control group. The vividness of the MI during MI + AO training was significantly greater in the moderate-difficulty vs. the remarkably-high-difficulty group. These results suggest that performing MI training while observing movement at a level that is moderately higher than an individual's ability can promote improvements in motor skills (close to a plateau state) in rehabilitation and sports training. The vividness of MI may be an important index for determining the difficulty level of the movement to be observed during MI + AO training.     

Assessing the impact of dual-task reactive step practice in people with Parkinson's disease: A feasibility study

Reactive stepping is impaired in people with Parkinson's Disease (PD) but can be improved with training. However, it is unclear if reactive steps can be improved when performing a concurrent cognitive task, a common and fall-relevant circumstance. We assessed the feasibility and preliminary effectiveness of dual-task reactive step training. Specifically, we measured whether stepping and cognitive reaction time are improved after one day of dual-task reactive step practice and if improvements are retained 24 h later. Sixteen people with PD and 13 age-matched healthy controls (HC) underwent repeated from-stance support surface perturbations that elicited a reactive step while performing an auditory Stroop task. Participants returned the following day to reassess dual-task reactive stepping performance. Cognitive, neuromuscular, and stepping outcomes were calculated. Increased step lengths were observed for both groups after practice (p < 0.001). Cognitive reaction times also improved through practice; however, this was more pronounced in the HC group (group by time interaction- p < 0.001). No changes were observed for step latency, margin of stability, or EMG onset through practice. Step length and cognitive reaction time improvements were retained 24 h after practice in both groups (step length: p < 0.001; cognitive reaction time: p = 0.05). This study provides preliminary evidence for the effectiveness of dual-task reactive step training to improve step length in people with PD. The improvements in step length without compromising cognitive reaction times suggest that participants improved reactive stepping without a robust attention shift toward the postural task. Future research is necessary to determine optimal training protocols and determine if such training protocols impact falls in PD patients.