Investigations of visually guided target-directed movement frequently adopt measures of within-participant spatial variability to infer the contribution of planning and control. The present study aims to verify this current trend by exploring the distribution of displacements at kinematic landmarks with a view to understand the potential sources of variability. Separate sets of participants aiming under full visual feedback conditions revealed a comparatively normal distribution for the displacements at peak velocity and movement end. However, there was demonstrable positive skew in the displacement at peak acceleration and a significant negative skew at peak deceleration. The ranges of the distributions as defined by either ±1SD or ±34.13th percentile (equivalent to an estimated 68.26% of responses) also revealed differences at peak deceleration. These findings indicate that spatial variability in the acceleration domain features highly informative systematic, as well as merely inherent, sources of variability. Implications for the further quantification of trial-by-trial behavior are discussed.
James W. Roberts, James Lyons, Daniel B. L. Garcia, Raquel Burgess, and Digby Elliott
The multiple process model contends that there are two forms of online control for manual aiming: impulse regulation and limb-target control. This study examined the impact of visual information processing for limb-target control. We amalgamated the Gunslinger protocol (i.e., faster movements following a reaction to an external trigger compared with the spontaneous initiation of movement) and Müller-Lyer target configurations into the same aiming protocol. The results showed the Gunslinger effect was isolated at the early portions of the movement (peak acceleration and peak velocity). Reacted aims reached a longer displacement at peak deceleration, but no differences for movement termination. The target configurations manifested terminal biases consistent with the illusion. We suggest the visual information processing demands imposed by reacted aims can be adapted by integrating early feedforward information for limb-target control.
Robert G. Weaver, Aaron Beighle, Heather Erwin, Michelle Whitfield, Michael W. Beets, and James W. Hardin
Background: Direct observation protocols may introduce variability in physical activity estimates. Methods: Thirty-five physical education lessons were video recorded and coded using the System for Observing Fitness Instruction Time (SOFIT). A multistep process examined variability in moderate to vigorous physical activity (MVPA%; walking + vigorous/total scans). Initially, per-SOFIT protocol MVPA% (MVPA%SOFIT) estimates were produced for each lesson. Second, true MVPA% (mean MVPA% of all students using all observations, MVPA%true) estimates were calculated. Third, MVPA% (MVPA%perm) was calculated based on all permutations of students and observation order. Fourth, physical education lessons were divided into 2 groups with 5 lessons from each group randomly selected 10,000 times. Group MVPA%perm differences between the 10 selected lessons were compared with the MVPA%true difference between group 1 and group 2. Results: Across all lessons, 10,212,600 permutations were possible (average 291,789 combinations per lesson; range = 73,440–570,024). Across lessons, the average absolute difference between MVPA%true and MVPA%SOFIT estimates was ±4.8% (range = 0.1%–17.5%). Permutations, based on students selected and observation order, indicated that the mean range of MVPA%perm estimates was 41.6% within a lesson (range = 29.8%–55.9%). Differences in MVPA% estimates between the randomly selected groups of lessons varied by 32.0%. Conclusion: MVPA% estimates from focal child observation should be interpreted with caution.
Byron Lai, Katie Cederberg, Kerri A. Vanderbom, C. Scott Bickel, James H. Rimmer, and Robert W. Motl
This review examined demographic and clinical characteristics of participants from exercise trials in 3 neurologic disability conditions (multiple sclerosis, spinal cord injury, and traumatic brain injury) and compared these data with population-based statistics. The authors included 75 published studies from 2006 to 2016: 53 studies for multiple sclerosis (n = 2,034), 14 for spinal cord injury (n = 302), and 8 for traumatic brain injury (n = 272). Pooled data resembled some heterogeneous aspects of population data sets. However, many characteristics were not reported; samples were small and predominantly White, and 48.1% of the people screened were excluded. Thus, findings from these studies may not be translatable across the range of people with these three conditions, which warrant efforts to target the inclusion of underrepresented subgroups in future exercise trials.
James W. Roberts, Nicholas Gerber, Caroline J. Wakefield, and Philip J. Simmonds
The failure of perceptual illusions to elicit corresponding biases within movement supports the view of two visual pathways separately contributing to perception and action. However, several alternative findings may contest this overarching framework. The present study aimed to examine the influence of perceptual illusions within the planning and control of aiming. To achieve this, we manipulated and measured the planning/control phases by respectively perturbing the target illusion (relative size-contrast illusion; Ebbinghaus/Titchener circles) following movement onset and detecting the spatiotemporal characteristics of the movement trajectory. The perceptual bias that was indicated by the perceived target size estimates failed to correspondingly manifest within the effective target size. While movement time (specifically, time after peak velocity) was affected by the target configuration, this outcome was not consistent with the direction of the perceptual illusions. These findings advocate an influence of the surrounding contextual information (e.g., annuli) on movement control that is independent of the direction predicted by the illusion.
Peter W. Harrison, Lachlan P. James, David G. Jenkins, Michael R. McGuigan, Robert W. Schuster, and Vincent G. Kelly
Purpose: The aim of this study was to map responses over 32 hours following high-load (HL) and moderate-load (ML) half-squat priming. Methods: Fifteen participants completed control, HL (87% 1RM), and ML (65% 1RM) activities in randomized, counterbalanced order. Countermovement jump (CMJ), squat jump (SJ), saliva testosterone, saliva cortisol, and perceptual measures were assessed before and 5 minutes, 8 hours, 24 hours, and 32 hours after each activity. Results are presented as percentage change from baseline and 95% confidence interval (CI). Cliff delta was used to determine threshold for group changes. Results: SJ height increased by 4.5% (CI = 2.2–6.8, Cliff delta = 0.20) 8 hours following HL. CMJ and SJ improved by 6.1% (CI = 2.1–7.8, Cliff delta = 0.27) and 6.5% (CI = 1.2–11.8, Cliff delta = 0.30), respectively, 32 hours after ML. No clear diurnal changes in CMJ or SJ occurred 8 hours following control; however, increases of 3.9% (CI = 2.9–9.2, Cliff delta = 0.26) and 4.5% (CI = 0.9–8.1, Cliff delta = 0.24), respectively, were observed after 32 hours. Although diurnal changes in saliva hormone concentration occurred (Cliff delta = 0.37–0.92), the influence of priming was unclear. Perceived “physical feeling” was greater 8 hours following HL (Cliff delta = 0.36) and 32 hours after ML and control (Cliff delta = 0.17–0.34). Conclusions: HL priming in the morning may result in small improvements in jump output and psychophysiological state in the afternoon. Similar improvements were observed in the afternoon the day after ML priming.
James W. Youdas, Hannah E. Baartman, Brian J. Gahlon, Tyler J. Kohnen, Robert J. Sparling, and John H. Hollman
Context: Suspension training devices use body weight resistance and unstable support surfaces that may facilitate muscle recruitment during push-up exercises. Objective: The authors examined muscle recruitment with surface electromyography on 4 shoulder and 4 torso muscles during (1) standard push-ups, (2) feet-suspended push-ups, (3) hands-suspended push-ups, and (4) dual-instability push-ups in which feet were suspended and hands were on unstable surfaces. Design: Cross-sectional design with repeated measures. Setting: Biomechanics laboratory. Participants: Thirty-two healthy men and women (mean age, 24.3 y; mean body mass index, 24.6 kg·m−2) participated. Intervention: Participants were tested while performing 2 repetitions each of 4 variations of push-ups. Main Outcome Measures: Muscle recruitment, normalized to maximum voluntary isometric contraction, was measured in 4 prime movers (anterior deltoid, pectoralis major, serratus anterior, and triceps brachii) and 4 torso stabilizers (external oblique, internal oblique, rectus abdominis, and upper erector spinae). Results: Muscle recruitment in the anterior deltoid, pectoralis major, and serratus anterior during suspended exercises was no greater than during standard push-ups. In contrast, torso stabilizer recruitment was significantly greater in the external oblique, internal oblique, and rectus abdominis during all 3 suspended exercises compared with standard push-ups. Suspended exercises under a dual-instability condition did not generate greater levels of muscle activation compared with conditions of single instability. Conclusions: Push-ups performed with suspension training systems may provide benefit if one’s goal is to enhance torso muscle training. One unstable surface may be sufficiently challenging for the client or athlete when performing push-up exercises with a suspension training device.
Patrick J. O’Connor, Melanie S. Poudevigne, M. Elaine Cress, Robert W. Motl, and James F. Clapp III
Describe safety and efficacy of a supervised, low-to-moderate intensity strength training program adopted during pregnancy among women at increased risk for back pain.
32 women adopted strength training twice per week for 12 weeks. Data on musculoskeletal injuries, symptoms, blood pressure, and the absolute external load used for 5 of 6 exercises were obtained during each session. A submaximal lumbar extension endurance exercise test was performed at weeks 5, 10, and 13.
The mean (± SD) exercise session attendance rate was 80.5% (± 11.3%). No musculoskeletal injuries occurred. Potentially adverse symptoms (eg, dizziness) were infrequent (2.1% of sessions). Repeated-measures ANOVA showed large increases in the external load across 12 weeks (all P values < .001) and the percentage increases in external load from weeks 1 to 12 were 36% for leg press, 39% for leg curl, 39% for lat pull down, 41% for lumbar extension and 56% for leg extension. Training was associated with a 14% increase in lumbar endurance. Blood pressure was unchanged following acute exercise sessions and after 12 weeks of exercise training.
The adoption of a supervised, low-to-moderate intensity strength training program during pregnancy can be safe and efficacious for pregnant women.
Anthony J. Lisi, Conor W. O’Neill, Derek P. Lindsey, Robert Cooperstein, Elaine Cooperstein, and James F. Zucherman
This paper presents the first reported measurements of lumbar intervertebral disc pressure in vivo during spinal manipulation. A pressure transducer was inserted into the nucleus pulposus of one normal-appearing lumbar disc in an asymptomatic adult volunteer. Pressures were recorded during several body positions and maneuvers, then during spinal manipulation, and lastly during a repetition of the preintervention body positions. Baseline pressures in the prone and side-lying positions measured 110 kPa and 150 kPa, respectively. During the manipulation, pressure rose to a peak of 890 kPa over 250 ms. Immediately following, pressures in the prone and side-lying positions measured 150 kPa and 165 kPa, respectively. These data do not support the hypotheses that manipulation can reduce a herniation by decreasing intradiscal pressure, or cause a herniation by raising pressure to failure levels. Further work may lead to a better understanding of this treatment method.
Parinda Khatri, James A. Blumenthal, Michael A. Babyak, W. Edward Craighead, Steve Herman, Teri Baldewicz, David J. Madden, Murali Doraiswamy, Robert Waugh, and K. Ranga Krishnan
The effects of a structured exercise program on the cognitive functioning of 84 clinically depressed middle-aged and older adults (mean age = 57 years) were examined. Participants were randomized to either 4 months of aerobic exercise (n = 42) or antidepressant medication (n = 42). Assessments of cognitive functioning (memory, psychomotor speed, executive functioning, and attention/concentration), depression, and physical fitness (aerobic capacity and exercise endurance) were conducted before and after the intervention. Exercise-related changes (accounting for baseline levels of cognitive functioning and depression) were observed for memory (p = .01) and executive functioning (p = .03). There were no treatment-group differences on tasks measuring either attention/concentration or psychomotor speed. Results indicate that exercise can exert influence on specific areas of cognitive functioning among depressed older adults. Further research is necessary to clarify the kinds of cognitive processes that are affected by exercise and the mechanisms by which exercise affects cognitive functioning.