Evidence of muscular adaptations within four weeks of barbell training in women

We investigated the time course of neuromuscular and hypertrophic adaptations associated with only four weeks of barbell squat and deadlift training. Forty-seven previously untrained women (mean ± SD, age = 21 ± 3 years) were randomly assigned to low volume training (n = 15), moderate volume training (n = 16), and control (n = 16) groups. The low and moderate volume training groups performed two and four sets, respectively, of five repetitions per exercise, twice a week. Testing was performed weekly, and included dual X-ray absorptiometry and vastus lateralis and rectus femoris B-mode ultrasonography. Bipolar surface electromyographic (EMG) signals were detected from the vastus lateralis and biceps femoris during isometric maximal voluntary contractions of the leg extensors. Significant increases in lean mass for the combined gynoid and leg regions for the low (+0.68 kg) and moderate volume (+0.47 kg) groups were demonstrated within three weeks. Small-to-moderate effect sizes were shown for leg lean mass, vastus lateralis thickness and pennation angle, and peak torque, but EMG amplitude was unaffected. These findings demonstrated rapid muscular adaptations in response to only eight sessions of back squat and deadlift training in women despite the absence of changes in agonist–antagonist EMG amplitude.     

Do kinematic metrics of walking balance adapt to perturbed optical flow?

Visual (i.e., optical flow) perturbations can be used to study balance control and balance deficits. However, it remains unclear whether walking balance control adapts to such perturbations over time. Our purpose was to investigate the propensity for visuomotor adaptation in walking balance control using prolonged exposure to optical flow perturbations. Ten subjects (age: 25.4 ± 3.8 years) walked on a treadmill while watching a speed-matched virtual hallway with and without continuous mediolateral optical flow perturbations of three different amplitudes. Each of three perturbation trials consisted of 8 min of prolonged exposure followed by 1 min of unperturbed walking. Using 3D motion capture, we analyzed changes in foot placement kinematics and mediolateral sacrum motion. At their onset, perturbations elicited wider and shorter steps, alluding to a more cautious, general anticipatory balance control strategy. As perturbations continued, foot placement tended toward values seen during unperturbed walking while step width variability and mediolateral sacrum motion concurrently increased. Our findings suggest that subjects progressively shifted from a general anticipatory balance control strategy to a reactive, task-specific strategy using step-to-step adjustments. Prolonged exposure to optical flow perturbations may have clinical utility to reinforce reactive, task-specific balance control through training.     

H-reflex excitability is inhibited in soleus,but not gastrocnemius,at the short-latency response of a horizontal jump-landing task

Impaired spinal-level neuromuscular control is suggested to contribute to instability and injury during dynamic landing tasks. Despite this suggestion, spinal-level neuromuscular control is yet to be examined during a horizontal jump-landing task. The aim of the current study was to assess changes in H-reflexes and its reliability at the short-latency response of landings from short and long distances. Eight healthy individuals (five male, three female; age, 22 ± 1.2 yrs; height, 178 ± 8.1 cm; weight, 72 ± 15.7 kg) participated in the study. H-reflexes were evoked at the SLR in the soleus and medial gastrocnemius muscles, during two landing conditions: 25% and 50% of maximal broad jump distance. H-reflexes were expressed relative to the background electromyography (EMG) and maximal M-wave responses (M-max). Soleus H-reflexes were inhibited when landing from shorter distance (25%, 13.9 ± 7.6%; 50%, 8.3 ± 6.5%; p < 0.01). No change in H-reflex excitability was observed in medial gastrocnemius. Background EMG was unaltered across landing conditions. Inhibition of soleus H-reflex excitability from 25% to 50% landing condition indicates a reduced contribution of Ia-afferent feedback to the alpha-motor neuron during landings from greater distances, which may contribute to stiffness regulation at the ankle joint. Unaltered H-reflex excitability of medial gastrocnemius is most likely attributed to its functional role during the landing task.     

Walking impairs cognitive performance among people with multiple sclerosis but not controls

People with multiple sclerosis (MS) complain of problems completing two tasks simultaneously; sometimes called ‘dual-tasking’ (DT). Previous research in DT among people with MS has focused on how adding a cognitive task interferes with gait and few have measured how adding a motor task could interfere with cognition. We aimed to determine the extent to which walking affects a concurrent working memory task in people with MS compared to healthy controls. We recruited MS participants (n = 13) and controls (n = 10) matched by age (±3 years), education (±3 years) and gender. Participants first completed the cognitive task (subtracting 7’s from the previous number) and then again while walking on an instrumented walkway. Although there were no baseline differences in cognition or walking between MS participants and controls, MS participants demonstrated a 52% decrease in number of correct answers during DT (p < 0.001). Mental Tracking Rate (% correct answers/min) correlated strongly with MS-related disability measured using the Expanded Disability Status Scale (EDSS; r(11) = −0.68, p < 0.01). We propose that compromised mental tracking during walking could be related to limited neural resource capacity and could be a potentially useful outcome measure to detect ecologically valid dual tasking impairments.     

Bicyclists’ speed adaptation strategies when conducting self-paced vs. system-paced smartphone tasks in traffic

The increasing prevalence of mobile phone usage while cycling has raised concerns, even though the number of cyclists involved in accidents does not increase at a comparable rate. A reason for this may be how cyclists adapt travelling speed and task execution to the current traffic situation. The aim of this study is to investigate speed adaptation among cyclists when conducting self-paced (initiated by the cyclist) vs. system-paced (initiated by somebody else) smartphone tasks in real traffic.Twenty-two cyclists completed a track in real traffic while listening to music, receiving and making calls, receiving and sending text messages, and searching for information on the internet. The route and the types of tasks were controlled, but the cyclists could choose rather freely when and where along the route to carry out the tasks, thus providing semi-naturalistic data on compensatory behaviour.The results clearly show that cyclists use conscious strategies to adapt their speed to accommodate the execution of secondary phone tasks. Regarding tactical behaviour, it was found that cyclists kept on cycling in 80% of the system-paced cases and in 70% of the self-paced cases. In the remaining cases, the cyclists chose to execute the phone task while standing still or when walking. Compared to the baseline (17.6 ± 3.5 km/h), the mean speed was slightly increased when the cyclists listened to music (18.2 ± 3.7 km/h) and clearly decreased when they interacted with the phone (13.0 ± 5.0 km/h). The speed reduction profile differed between self-paced and system-paced tasks with a preparatory speed reduction before task initiation for self-paced tasks.In conclusion, when the cyclists had the chance they either stopped or adapted their speed proactively to accommodate the execution of the phone task. For self-paced tasks, the speed reduction was finalised before task initialisation, and for system-paced tasks the speed adaptation occurred in reaction to the incoming task. It is recommended to investigate whether the observed compensatory behaviour is enough to offset the possible negative effects of smartphone use.     

Biomechanical analysis of gait termination in 11–17 year old youth at preferred and fast walking speeds

In populations where walking and/or stopping can be difficult, such as in children with cerebral palsy, the ability to quickly stop walking may be beyond the child’s capabilities. Gait termination may be improved with physical therapy. However, without a greater understanding of the mechanical requirements of this skill, treatment planning is difficult. The purpose of this study was to understand how healthy children successfully terminate gait in one step when walking quickly, which can be challenging even for healthy children. Lower extremity kinematic and kinetic data were collected from 15 youth as they performed walking, planned, and unplanned stopping tasks. Each stopping task was performed as the subject walked at his/her preferred speed and a fast speed. The most significant changes in mechanics between speed conditions (preferred and fast) of the same stopping task were greater knee flexion angles (unplanned: +16.49 ± 0.54°, p = 0.00; planned: +15.75 ± 1.1°, p = 0.00) and knee extension moments (unplanned: +0.67 ± 0.02 N/kgm, p = 0.00; planned: +0.57 ± 0.23 N/kgm, p = 0.00) at faster speeds. The extra range of motion in the joints and extra muscle strength required to maintain the stopping position suggests that stretching and strengthening the muscles surrounding the joints of the lower extremity, particularly the knee, may be a useful intervention.     

Effect of instructions on EMG during the bench press in trained and untrained males

Strength and rehabilitation professionals strive to emphasize certain muscles used during an exercise and it may be possible to alter muscle recruitment strategies with varying instructions. This study aimed to determine whether resistance trained and untrained males could selectively activate the pectoralis major or triceps brachii during the bench press according to various instructions. This study included 13 trained males (21.5 ± 2.9 years old, 178.7 ± 7.0 cm, 85.7 ± 10.7 kg) and 12 untrained males (20.3 ± 1.6 years old, 178.8 ± 9.4 cm, 74.6 ± 17.3 kg). Participants performed a bench press one-repetition maximum (1-RM) test, 3 uninstructed repetitions at 80% 1-RM and two more sets of three repetitions with instructions to isolate the chest or arm muscles. Electromyography (EMG) was obtained from the pectoralis major, anterior deltoid, and the long head and short head of the triceps brachii. Maximum EMG activity normalized to 1-RM for each muscle was averaged over the three repetitions for each set and compared between the uninstructed, chest-instructed and arm-instructed conditions among the groups. The trained participants had a greater 1-RM (126.2 ± 30.6 kg) than the untrained participants (61.6 ± 14.8 kg) (P < 0.01). EMG activity was not different between the groups for any of the instructions (P > 0.05). When the group data was combined, short head of the triceps activity was significantly lower in the chest instruction (80.1 ± 19.3%) when compared to the uninstructed (85.6 ± 23.3%; P = 0.01) and arm-instructed (86.0 ± 23.2; P = 0.01) conditions. It can be concluded that instructions can affect muscle activation during the bench press, and this is not dependent on training status.     

Contextual effects on activity profiles of domestic field hockey during competition and training

Game context is widely accepted to influence performance but most data available is ‘categorical’ and addresses performance rather than activity. This study assessed direct effects of opposition and team ranking in field hockey to establish influences on activity. One hundred and eight (n = 108) female field hockey players (age 16–39 years) participated, giving 186 competition and 48 training analyses. Team average distance (mean ± SD) observed in a mid-ranked team during competition ranged from 5949 ± 611 to 7719 ± 257 m demonstrating an opposition rank effect (Pearson’s r = .71; adjusted R² = .42). However, multiple linear regression analysis demonstrated a stronger relationship in lower ranked teams (Pearson’s r = .99; adjusted R² = .97 through 3–9). In contrast, no team rank effect was observed during randomly monitored competition where team average distance ranged from 5177 ± 444 to 7316 ± 241 m (Pearson’s r = .15 and adjusted R² = .12). In training, however, a team rank effect was observed in distance-related performance indicators where team average distance during small-sided games ranged from 5877 ± 188 to 3551 ± 193 m drill (per 70 min) with Pearson’s r = .95 and adjusted R² = .87. The presence of contextual effects has significant practical implications for team sports where the training load assumed from competition may be overestimated.     

Children’s age modulates the effect of part and whole practice in motor learning

Motor skills can be learned by practicing the whole or part of a movement. In whole practice (WP), a skill is acquired by practicing the movement in its entirety, whereas in part practice (PP), a task is learned by practicing its components before combining them. However, the effectiveness of WP and PP in children is unclear. We, therefore, examined the effects of WP and PP on the learning of juggling among first-, third-, and fifth-graders. Children of each grade were pseudo-randomly assigned to the WP or PP group to learn cascade juggling in 6 days. After baseline assessments, the WP learners practiced three-beanbag juggling. The PP learners practiced one-beanbag juggling on the first 2 days, two-beanbag juggling on the following 2 days, and three-beanbag juggling on the last 2 days. Practice consisted of 40 trials each day. Skill retention and transfer trials (juggling in the opposite direction) were measured 24 h after training (number of catches). There was no significant difference between WP and PP in skill retention (WP: 1.28 ± 0.73; PP: 1.42 ± 046, p = .40) and transfer (WP: 1.31 ± 0.78; PP: 1.37 ± 0.55, p = .49). However, a time × grade × group interaction (p < .001) was observed in retention. Children of different grades received differential benefits from the WP and PP regimens. The fifth-graders learned better using WP, whereas the first- and third-graders showed better learning with PP. We discuss the three possible explanations for the results (neural maturity, explicit learning, and coordination capabilities).     

Neuromechanical synergies in single-leg landing reveal changes in movement control

Our purpose was to examine changes in single-leg landing biomechanics and movement control following alterations in mechanical task demands via external load and landing height. We examined lower-extremity kinematic, kinetic, and electromyographic (EMG) adjustments, as well as changes in movement control from neuromechanical synergies using separate principal component analyses (PCA). Nineteen healthy volunteers (15M, 4F, age: 24.3 ± 4.9 y, mass: 78.5 ± 14.7 kg, height: 1.73 ± 0.08 m) were analyzed among 9 single-leg drop landing trials in each of 6 experimental conditions (3 load and 2 landing height) computed as percentages of subject bodyweight (BW, BW + 12.5%, BW + 25%) and height (H12.5% & H25%). Condition order was counterbalanced, including: 1.) BW·H12.5, 2.) BW + 12.5·H12.5, 3.) BW + 25·H12.5, 4.) BW·H25, 5.) BW + 12.5·H25, 6.) BW + 25·H25. Lower-extremity sagittal joint angles and moments (hip, knee, & ankle), vertical ground reaction force (GRFz), and electrical muscle activity (gluteus maximus, biceps femoris, vastus medialis, medial gastrocnemius, & tibialis anterior muscles), were analyzed in each trial. Biomechanical adjustments and neuromechanical synergies were assessed using PCA. Subjects reduced effective landing height through segmental configuration adjustments at ground contact, extending at the hip and ankle joints with greater load and landing height (p ⩽ 0.028 and p ⩽ 0.013, respectively), while using greater medial gastrocnemius pre-activation with greater load (p ⩽ 0.006). Dimension reduction was observed under greater mechanical task demands, compressing and restructuring synergies among patterns of muscle activation, applied loads, and segmental configurations. These results provide insight into movement control and potential injury mechanisms in landing activities.     

Effect of an intensified training period on well-being indices,recovery and psychological aspects in professional soccer players

IntroductionIntensified training periods (IT) are associated with fatigue increase and psychological variations.ObjectiveThis investigation aimed to examine the perceived well-being, recovery quality and psychological responses during an IT.MethodsFifteen professional soccer players (mean ± SD: age: 24 ± 1 years, body mass: 71.3 ± 15.1 kg, height: 178.0 ± 6.1 cm) completed a 6-week training program consisting of 2 weeks of basic training (BT) and 4 weeks of IT. They were tested before (T1) and after (T2) the IT. Training load (TL) perception, strain and monotony were measured by the session-RPE method. Well-being indices (sleep quality, fatigue level, stress and delayed-onset muscular soreness [DOMS]) and total quality recovery (TQR) were recorded before each training session. The profile of mood states (POMS) and the Ottowa mental skills assessment tool (OMSAT)-3 were conducted before and after IT.ResultsNo significant difference was found after IT in OMSAT-3 scores (p > 0.05). TL, monotony and strain increased during IT (p < 0.001). Moreover, well-being indices (stress, sleep quality, fatigue level and DOMS) increased (p < 0.001) and TQR decreased (p < 0.001) during IT. The IT increased total mood disturbance (TMD, p < 0.001), tension (p < 0.05) and fatigue (p < 0.01) and decreased vigor (p < 0.001). Significant relationships were found between TL and Hooper Index (HI), TQR and TMD (r = 0.58, 0.65, −0.57, respectively; all p < 0.05).ConclusionThe findings of this investigation suggested that mental ability was not sensitive to fatigue caused by training load intensification. However, perceived well-being, recovery state and mood were found to be sensitive measures and may provide coaches with information about wellness and psychological state of soccer players during IT.     

The effect of a motor skills training program in the improvement of practiced and non-practiced tasks performance in children with developmental coordination disorder (DCD)

The purpose of the present study was to examine the effect of a group-based task oriented skills training program on motor and physical ability for children with DCD. It was also investigated if there was an effect on fine motor and handwriting tasks that were not specifically practiced during the training program. Forty-one children aged 6–10 years took part in this study. Children were assigned to three groups: an experimental training group consisting of 14 children with DCD, a control non-training group consisted of 13 children with DCD and a control non-training group consisting of 14 typically developed children. The measurements included were, the Movement Assessment Battery for Children (MABC), the Modified Agility Test (MAT), the Triple Hop Distance (THD), the 5 Jump-test (5JT) and the Handwriting Performance Test. All measures were administered pre and post an 8-week training program. The results showed that 10 children of the DCD training-group improved their performance in MABC test, attaining a score above the 15th percentile after their participation in the training program. DCD training-group showed a significant improvement on all cluster scores (manual dexterity (t (13) = 5.3, p < .001), ball skills (t (13) = 2.73, p < .05) and balance (t (13) = 5.13, p < .001). Significant performance improvements were also found in MAT, THD, 5JT (t (13) = –4.55; p < .01), handwriting quality (t (12) = –2.73; p < .05) and speed (t (12) = –4.2; p < .01) after the training program. In conclusion, improvement in both practiced and non-practiced skills, in the training program, may reflect improvement in motor skill but also transfer to other skills.     

Proprioceptive impairments associated with knee osteoarthritis are not generalized to the ankle and elbow joints

The mechanisms for proprioceptive changes associated with knee osteoarthritis (OA) remain elusive. Observations of proprioceptive changes in both affected knees and other joints imply more generalized mechanisms for proprioceptive impairment. However, evidence for a generalized effect remains controversial. This study examined whether joint repositioning proprioceptive deficits are localized to the diseased joint (knee) or generalized across other joints (elbow and ankle) in people with knee OA. Thirty individuals with right knee OA (17 female, 66 ± 7 [mean ± SD] years) of moderate/severe radiographic disease severity and 30 healthy asymptomatic controls of comparable age (17 female, 65 ± 8 years) performed active joint repositioning tests of the knee, ankle and elbow in randomised order in supine. Participants with knee OA had a larger relative error for joint repositioning of the knee than the controls (OA: 2.7 ± 2.1°, control: 1.6 ± 1.7°, p = .03). Relative error did not differ between groups for the ankle (OA: 2.2 ± 2.5°, control: 1.9 ± 1.3°, p = .50) or elbow (OA: 2.5 ± 3.3°, control: 2.9 ± 2.8°, p = .58). These results are consistent with a mechanism for proprioceptive change that is localized to the knee joint. This could be mediated by problems with mechanoreceptors, processing/relay of somatosensory input to higher centers, or joint-specific interference with cognitive processes by pain.     

Motor imagery ability and internal representation of movement in children with probable developmental coordination disorder

It has been hypothesised that deficits in the functioning of the mirror neuron system (MNS) and internal modelling may contribute to the motor impairments associated with DCD. These processes can be explored behaviourally through motor imagery paradigms. Motor imagery proficiency of children with and without probable DCD (pDCD) was examined using a complex hand rotation task to explore whether motor imagery strategies could be used during more complex tasks. Forty-four boys aged 7–13 years participated, 22 with pDCD (mean = 9.90 years ± 1.57) and 22 controls (mean = 9.68 years ± 1.53). Participants completed the task twice: with and without motor imagery instructions. Stimuli were presented in two rotational axes – palm/back, and eight 45° rotational steps. Both groups showed evidence of following the biomechanical and postural constraints of actual movements. Responses of children with pDCD were slower and less accurate than controls, with group differences increasing alongside task complexity. A greater impact of biomechanical constraints for accuracy was observed in the DCD group. The response characteristics of children with pDCD likely reflects a reduced capacity to mentally manipulate a body schema and reduced visuo-motor processing capabilities. Behaviourally, these processes are linked to MNS and internal modelling function, suggesting deficits in these systems may contribute to the movement difficulties characteristic of DCD.     

Partial body weight support treadmill training speed influences paretic and non-paretic leg muscle activation,stride characteristics,and ratings of perceived exertion during acute stroke rehabilitation

BackgroundIntensive task-specific training is promoted as one approach for facilitating neural plastic brain changes and associated motor behavior gains following neurologic injury. Partial body weight support treadmill training (PBWSTT), is one task-specific approach frequently used to improve walking during the acute period of stroke recovery (<1 month post infarct). However, only limited data have been published regarding the relationship between training parameters and physiologic demands during this early recovery phase.ObjectiveTo examine the impact of four walking speeds on stride characteristics, lower extremity muscle demands (both paretic and non-paretic), Borg ratings of perceived exertion (RPE), and blood pressure.DesignA prospective, repeated measures design was used.MethodsTen inpatients post unilateral stroke participated. Following three familiarization sessions, participants engaged in PBWSTT at four predetermined speeds (0.5, 1.0, 1.5 and 2.0 mph) while bilateral electromyographic and stride characteristic data were recorded. RPE was evaluated immediately following each trial.ResultsStride length, cadence, and paretic single limb support increased with faster walking speeds (p ⩽ 0.001), while non-paretic single limb support remained nearly constant. Faster walking resulted in greater peak and mean muscle activation in the paretic medial hamstrings, vastus lateralis and medial gastrocnemius, and non-paretic medial gastrocnemius (p ⩽ 0.001). RPE also was greatest at the fastest compared to two slowest speeds (p < 0.05).ConclusionsDuring the acute phase of stroke recovery, PBWSTT at the fastest speed (2.0 mph) promoted practice of a more optimal gait pattern with greater intensity of effort as evidenced by the longer stride length, increased between-limb symmetry, greater muscle activation, and higher RPE compared to training at the slowest speeds.     

Evaluating feedback time delay during perturbed and unperturbed balance in handstand

Feedback delays in balance are often assessed using muscle activity onset latencies in response to discrete perturbations. The purpose of the study was to calculate EMG latencies in perturbed handstand, and determine if delays are different to unperturbed handstand. Twelve national level gymnasts completed 12 perturbed and 10 unperturbed (five eyes open and five closed) handstands. Forearm EMG latencies during perturbed handstands were assessed against delay estimates calculated via: cross correlations of wrist torque and COM displacement, a proportional and derivative model of wrist torque and COM displacement and velocity (PD model), and a PD model incorporating a passive stiffness component (PS-PD model). Delays from the PD model (161 ± 14 ms) and PS-PD model (188 ± 14 ms) were in agreement with EMG latencies (165 ± 14 ms). Cross correlations of COM displacement and wrist torque provided unrealistically low estimates (5 ± 9 ms). Delays were significantly lower during perturbed (188 ± 14 ms) compared to unperturbed handstand (eyes open: 207 ± 12 ms; eyes closed: 220 ± 19 ms). Significant differences in delays and model parameters between perturbed and unperturbed handstand support the view that balance measures in perturbed testing should not be generalised to unperturbed balance.     

Technique determinants of knee joint loads during cutting in female soccer players

The aim of this study was to investigate the relationships between technique characteristics and knee abduction moments during 90° cuts. A cross sectional design involving 26 elite and sub-elite female soccer players (mean ± SD; age: 21 ± 3.2 years, height: 1.68 ± 0.07 m, and mass: 59.1 ± 6.8 kg) was used to explore relationships between pre-determined technical factors on knee abduction moments during cutting. Three dimensional motion analyses of 90° cuts on the right leg were performed using ‘Qualisys Pro Reflex’ infrared cameras (240 Hz). Ground reaction forces were collected from two AMTI force platforms (1200 Hz) embedded into the running track to examine 2nd last and last footfalls. Pearson’s correlation coefficients, co-efficients of determination and hierarchical multiple regression were used to explore relationships between a range of technique parameters and peak knee abduction moments. Significance was set at p < .05. Hierarchical multiple regression revealed that initial knee abduction angle, lateral leg plant distance and initial lateral trunk lean could explain 67% (62% adjusted) of the variation in peak knee abduction moments (F_(1,22) = 8.869, p = .007). These findings reveal potential modifiable technical factors to lower peak knee abduction moments during cutting.     

Enhanced retention of drop vertical jump landing technique: A randomized controlled trial

External focus instructions have been shown to result in superior motor performance compared to internal focus instructions. Using an EF may help to optimize current anterior cruciate ligament (ACL) injury prevention programs. The purpose of the current study was to investigate the effects of instructions on landing technique and performance by comparing an external focus (EF), internal focus (IF), video (VI) and control (CTRL) group. Subjects (age 22.50 ± 1.62 years, height 179.70 ± 10.43 cm, mass 73.98 ± 12.68 kg) were randomly assigned to IF (n = 10), EF (n = 10), VI (n = 10) or CTRL group (n = 10). Landing was assessed from a drop vertical jump (DVJ) in five sessions: pretest, two training blocks (TR1 and TR2) and directly after the training sessions (post test) and retention test 1 week later. Group specific instructions were offered in TR1 and TR2. Landing technique was assessed with the Landing Error Scoring System (LESS) and jump height was taken as performance measure. The results show that males in the VI group and females both in the VI and EF groups significantly improved jump-landing technique. Retention was achieved and jump height was maintained for males in the VI group and females both in the VI and EF groups. It is therefore concluded that EF and VI instructions have great potential in ACL injury prevention.     

Attention lapses and behavioural microsleeps during tracking,psychomotor vigilance,and dual tasks

This study examined the incidence of attention lapses and microsleeps under contrasting levels of task complexity during three tasks: PVT, 2-D tracking and a dual task combining the two. More attention lapses per participant (median 15 vs. 3; range 1–74 vs. 0–76, p = 0.001), with the greatest increase with time spent-on-task (p = 0.002), were evident on the more cognitively-demanding dual task than on the PVT. Conversely, fewer microsleeps (median 0 vs. 0; range 0–1 vs. 0–18, p = 0.022) occurred during the more complex task compared to the tracking task. An increase in microsleep rate with time spent-on-task (p = 0.035) was evident during the tracking task but not the dual task. These results indicate that the higher cognitive load, associated with an increase in task complexity, increased the likelihood of attention lapses, while a reduction in task complexity increased the likelihood of microsleeps.