Physiological and biomechanical responses to exercise on two different types of rowing ergometers in NCAA Division I oarswomen.

BACKGROUND: Stationary (SE) and dynamic (DE) rowing ergometers, that are utilized for indoor training and physical assessment of competitive rowers, may elicit different physiological and biomechanical responses. The present study used SE and DE ergometers to examine submaximal and peak physiological and biomechanical responses during an incremental rowing test. METHODS: Twelve National Collegiate Athletic Association (NCAA) Division I oarswomen performed seven-stage rowing tests with the last stage performed with maximal effort. Heart rate (HR), lactate (LA), oxygen uptake (VO2), ventilation (VE), stroke rate (SR), gross efficiency (GE), and rating of perceived exertion (RPE) were obtained; while trunk, hip, knee, shoulder, and elbow ranges of motion (ROM) were measured. RESULTS: SR was higher at maximal stage DE (29.3 vs. 34.8 strokes/min, p = 0.018, d = 1.213). No difference occurred in responses of maximal stage HR, RPE, VO2, VE, LA, or GE between the two ergometers. Submaximal LA and SR were greater on the DE for all submaximal stages. Submaximal VE was greater on the DE for all submaximal stages except Stage 3 (p = 0.160, d = 0.655). VO2 was higher on the DE Stages 2-5. GE was higher on the SE for Stages 2-5. Athletes showed increased trunk (p = 0.025, [Formula: see text] = 0.488) and knee (p = 0.004, [Formula: see text] = 0.668) ROM on SE. CONCLUSION: Rowing on the DE appears to elicit a greater stroke rate and more optimal joint angles especially at high intensities. Hence, the DE is worthy of consideration as a preferred ergometer for women rowers.

Cognitive Load Influences Drop Jump Landing Mechanics During Cognitive-Motor-Simulated Shooting.

INTRODUCTION: Military duties require immense cognitive-motor multitasks that may predispose soldiers to musculoskeletal injury. Most cognitive challenges performed in the research laboratory are not tactical athlete specific, limiting generalizability and transferability to in-field scenarios. The purpose of this study was to determine the impact of a cognitive-motor multitask (forward drop jump landing while simultaneously performing simulated shooting) on knee kinetics and kinematics. METHODS: Twenty-four healthy collegiate Reserve Officer's Training Corps members (18 males and 6 females, 20.42 ± 1.28 years, 174.54 ± 10.69 cm, 78.11 ± 14.96 kg) volunteered, and knee kinetics and kinematics were assessed between baseline and cognitive-loaded conditions. Repeated measures ANOVAs were conducted for each dependent variable with the within-subject factor of condition (baseline vs. cognitive load). RESULTS: Univariate ANOVAs indicated that knee flexion angle at initial contact (IC) (decreased 6.07°; d = 3.14), knee flexion displacement (increased 6.78°; d = 1.30), knee abduction angle at IC (increased 2.3°; d = 1.46), peak knee abduction angle (increased 3.04°; d = 0.77), and peak vertical ground reaction force (increased 0.81 N/kg; d = 2.13) were significant between conditions (P < .001). Therefore, cognitive load resulted in decreased knee flexion and increased knee abduction angle at IC and greater peak vertical ground reaction force, all factors commonly associated with knee injury risk. Peak knee flexion angle and knee abduction displacement were not significant between conditions (P > .05). CONCLUSIONS: Cognitive challenge induced knee landing biomechanics commonly associated with injury risk. Injury risk screening or return-to-training or duty assessments in military personnel might consider both baseline and cognitive conditions.

The effects of virtual reality immersion on drop landing mechanics.

Virtual reality (VR) can be used to alter the environment and challenge sensory calibration which rehabilitation and return-to-sport testing lack. The purpose was to establish how VR manipulation of the environment changes knee landing biomechanics. Twenty-nine healthy active adults (22 males; 20.52 ± 1.21 years; 1.75 ± 0.09 m; 78.34 ± 14.33 kg) were recruited. Three drop landing trials (31 cm height box) were performed for three conditions: eyes-open (EO), eyes-closed (EC), and VR, consisting of a head-mounted display of a 360° photo of a steep man-made edge or drop. Knee kinematics and kinetics were evaluated using 3D motion capture. The VR condition significantly increased Landing Error Score System errors relative to EO (1.28 ± 0.20, p < 0.001) and EC (0.98 ± 0.22, p < 0.001) and increased vertical ground reaction force relative to EO (0.41 ± 0.09 N·bw-1, p < 0.001) and EC (0.34 ± 0.07 N·bw-1, p < 0.001). The VR condition had less knee flexion at initial contact compared to EO (4.39 ± 0.75°, p = 0.001) and EC (1.83 ± 0.63°, p = 0.021). The VR condition had more knee abduction at initial contact compared to EO (0.71 ± 0.24°, p = 0.002) and EC (0.69 ± 0.22°, p = 0.002) and increased knee abduction at maximum flexion compared to EO (2.01 ± 0.58°, p = 0.026). Landing in VR increased injury risk landing biomechanics, indicating that VR may option to incorporate into return-to-play or injury risk assessment.

Cognitive Load Impairs Time to Initiate and Complete Shooting Tasks in ROTC Members.

INTRODUCTION: Multitasking typically requires an individual to simultaneously process cognitive information while performing a motor task. Cognitive motor interference (CMi) is encountered when cognitive challenges negatively impact motor task performance. Military personnel encounter cognitively taxing situations, especially during combat or other tactical performance scenarios, which may lead to injury or motor performance deficits (i.e., shooting inaccuracy, delayed stimulus-response time, and slowed movement speed). The purpose of the current study was to develop four cognitive motor shooting paradigms to determine the effects of cognitive load on shooting performance in healthy Reserve Officers' Training Corps (ROTC) cadets. METHODS: Thirty-two healthy collegiate ROTC members (24 male and 8 female; 20.47 ± 1.24 years, 174.95 ± 10.58 cm, and 77.99 ± 13.90 kg) were recruited to complete four simulated shooting tasks with additional "motor" challenge (180° turn, gait, weighted, and unweighted landing) and with and without a "cognitive" decision-making challenge requiring response selection and inhibition to both auditory and visual stimuli, totaling eight multi-task cognitive motor shooting conditions. The current study was approved by the university's Institutional Review Board. Task initiation (seconds), task completion (seconds), and number of misses were calculated to determine marksmanship efficiency and accuracy. For each task, a multivariate repeated-measures analysis of variance (ANOVA) was conducted for the combined dependent variables. If the overall multivariate repeated-measures ANOVA was significant, follow-up univariate ANOVAs were conducted for each dependent variable. Alpha was set at α = 0.05 for all analyses. RESULTS: Task initiation increased for the cognitive condition for the 180° turn (4.29 ± 1.22 seconds baseline, 5.09 ± 1.39 seconds cognitive; P < .05), gait (2.76 ± .60 seconds baseline, 3.93 ± .62 seconds cognitive; P < .05), unweighted (1.27 ± .57 seconds baseline, 3.39 ± .63 seconds cognitive; P < .05), and weighted landing (1.46 ± .72 seconds baseline, 3.35 ± .60 seconds cognitive; P < .05). Task completion time increased for the cognitive condition for the 180° turn (3.48 ± 1.53 seconds baseline, 4.85 ± 1.24 seconds cognitive; P < .05), gait (7.84 ± 2.07 seconds baseline, 9.23 ± 1.76 seconds cognitive; P < .05), unweighted (5.98 ± 1.55 seconds baseline, 7.45 ± 1.51 seconds cognitive; P < .05), and weighted landing (6.09 ± 1.42 seconds baseline, 7.25 ± 1.79 seconds cognitive; P < .05). There were no statistically significant differences in the number of misses for any of the tasks between conditions (P > .05). CONCLUSIONS: The addition of a cognitive load increased both task initiation and task completion times during cognitive motor simulated shooting. Adding cognitive loads to tactical performance tasks can result in CMi and negatively impact tactical performance. Thus, consideration for additional cognitive challenges into training may be warranted to reduce the potential CMi effect on tactical performance.

The Immediate Effects of Expert and Dyad External Focus Feedback on Drop Landing Biomechanics in Female Athletes: An Instrumented Field Study.

BACKGROUND: Anterior Cruciate Ligament (ACL) injury prevention interventions have used trained experts to ensure quality feedback. Dyad (peer) feedback may be a more cost-effective method to deliver feedback to athletes. PURPOSE: To determine the immediate effects of dyad versus expert feedback on drop landing kinematics and kinetics in female athletes. STUDY DESIGN: Cohort study. SETTING: College gymnasium. METHODS: Two teams (one female basketball and one female volleyball), from a local college, were team randomized to dyad feedback (volleyball team) or expert feedback (basketball team) (13 expert, 19±0.87years, 1.7±0.09m, 68.04±7.21kg) (10 dyad 19.4±1.07years, 1.73±0.08m, 72.18±11.23kg). Participants completed drop vertical jumps at two different time points (pre- and post-feedback). Knee flexion and abduction displacement were assessed with Inertial Measurement Units (IMUs) and vertical ground reaction force (vGRF) was assessed with a force plate during the landing phase of the drop vertical jump and compared across groups and condition (pre- and post-feedback) with a repeated measures ANCOVA a priori α <0.02 was set for multiple tests conducted. RESULTS: There were no significant differences between groups for flexion displacement. There was a significant change pre- to post- (decrease 4.65˚ p=0.01) in abduction displacement, with no group effect. There was a significant interaction of group by condition (p=0.01) for vGRF with no difference between groups before feedback (p>0.05). Between groups there was a decrease of vGRF in the expert group (difference 0.45 N*bw-1, p=0.01) at post-feedback relative to dyad. Within the expert group there was a significant difference between pre- and post-feedback (difference 0.72 N*bw-1, p=0.01), while the dyad group did not change pre- to post-feedback (difference 0.18 N*bw-1, p=0.67). CONCLUSION: Movement screening experts giving real-time feedback were successful in improving key injury-risk kinematics and kinetics in female athletes, while dyad feedback only improved kinematics, indicating that expert feedback may be needed to ensure changes in kinematics and kinetics. LEVEL OF EVIDENCE: 2.

The Effects of a Cognitive Dual Task on Jump-landing Movement Quality.

Investigations on movement quality deficits associated with jump landing are numerous, however, these studies are often performed in laboratories with little distraction to the participant. This is contrary to how injury typically occurs secondary to sport-specific distraction where the athlete is cognitively loaded during motor performance. Thus, the purpose of this study was to determine the effect of a cognitive load on jump-landing movement quality. A dual-task design was used to determine the effects of a dual-task on tuck jump movement quality in 20 participants. There were three cognitive conditions (no cognitive task, easy-cognitive task, and difficult-cognitive task). The dual task elicited statistically significant changes in overall tuck jump score (movement quality) across the conditions with tuck jump score increasing from 3.52±1.64 baseline to 4.37±1.25 with the easy-cognitive task to 4.67±1.24 with the difficult-cognitive task. The findings of this study may be useful to screen for individuals at risk of lower extremity injury utilizing the tuck jump when paired with a cognitive task. The screening would then identify individuals who may have poor neuromuscular control when cognitively loaded.

Symmetry does not Indicate Recovery: Single-leg Hop Before and After a Lower Extremity Injury.

Current recommendations for return-to-play decision-making involve comparison of the injured limb to the uninjured limb. However, the use of the uninjured limb as a comparison for hop testing lacks empirical evidence. Thus, the purpose of this study was to determine the effects of lower extremity injury on limb symmetry and performance on the single-leg hop for distance. Two-hundred thirty-six adolescent athletes completed the single-leg hop for distance before the beginning of the season (pre-injury). Forty-four adolescent athletes sustained a lower extremity injury (22 ankle and 12 knee) and missed at least three days of sports participation. All individuals had completed the single-leg hop for distance before the beginning of the season (pre-injury) and at discharge (post-injury). Injured limb single-leg hop for distance significantly decreased at return-to-play from pre-injury with a mean decrease of 48.9 centimeters; the uninjured limb also significantly decreased, with a mean decrease of 33.8 centimeters. Limb symmetry did not significantly change pre- to post-injury with a mean difference of 1.5%. Following a lower extremity injury, single-leg hop for distance performance degrades not only for the injured limb but also the uninjured limb. However, limb symmetry did not change following a lower extremity injury.

Postural stability during visual-based cognitive and motor dual-tasks after ACLR.

OBJECTIVES: Determine the effect of visual-based motor and cognitive dual tasking on postural stability in those with anterior cruciate ligament reconstruction relative to matched controls. DESIGN: Cohort study. METHODS: Fourteen volunteers with history of anterior crucaite ligament reconstruction were matched with fourteen healthy controls. Participants performed single leg balance tasks under 4 conditions: (1) single leg balance with eyes-open, (2) single leg balance while catching a ball (dual-motor), (3) single leg balance while repeating a string of numbers in reverse order after viewing them (dual-cognitive) and (4) single leg balance with eyes-closed. Participants completed several patient-reported outcomes of knee function. Mixed effects models were used to identify group differences on the center of pressure measures of ellipse area and root-mean-squared excursion (medial-lateral and anterior-posterior). The mixed models included subject pair as a random factor and group (control, anterior cruciate liagement reconstruction), balance condition (eyes-open, eyes-closed, dual-cognitive, and dual-motor), and group*condition as fixed effects. Tukey post-hoc pairwise comparisons were performed for significant interaction and main effects with an α=0.05. RESULTS: A significant group by condition interaction was observed for ellipse area and medial-lateral root-mean-squared excursion. The anterior cruciate ligament reconstruction group had higher ellipse area (p=0.002, d=0.44) and medial-lateral root-mean-squared excursion (p<0.001, d=0.49). CONCLUSIONS: Postural stability is greatly impaired under eyes-closed and dual-motor conditions relative to eyes-open. Anterior cruciate ligament reconstructed individuals have greater postural instability during the dual-cognitive condition that may indicate unique neural processing deficits remain following anterior cruciate ligament reconstruction.

Neurocognitive challenged hops reduced functional performance relative to traditional hop testing.

OBJECTIVE: Determine the relationship between four foundational single-leg hop tests and respective neurocognitive single-leg hop tests. DESIGN: Cross-sectional; SETTING: University gymnasium. PATIENTS OR OTHER PARTICIPANTS: Twenty-two participants (9 Male, 13 Female, 20.9 ± 2.5 years, 171.2 ± 11.7 cm, 70.3 ± 11.0 kg) were recruited. Maximum distance was measured for three hop tests (single-leg hop, single-leg crossover hop, single-leg triple hop) and fastest time was measured for the fourth (single-leg 6-m hop) for traditional and neurocognitive conditions. MAIN OUTCOME MEASURES: Pearson correlations were conducted to assess the relationship between the new neurocognitive hop and the analogous traditional hop. One repeated measures MANOVA was conducted for each leg to determine the difference in hop performance between hop conditions (traditional and neurocognitive) for the dependent variables. Alpha level was set at α < 0.05. RESULTS: Correlations ranged from 0.86 to 0.92 between traditional and neurocognitive hop tests. The repeated measures MANOVA was significant for condition for both legs (p < 0.05). Specifically, the crossover hop (average percent decrease 10.37%), triple hop (average percent decrease 7.13%), and 6-m hop (average percent decrease 81.67%) were statistically different between traditional and neurocognitive conditions (p < 0.05). CONCLUSION: The addition of neurocognitive reactive and anticipatory components to simulate more sport specific scenarios may improve functional testing for return to sport.

The effects of an unanticipated side-cut on lower extremity kinematics and ground reaction forces during a drop landing.

Unanticipated direction to cut after landing may alter the lower extremity landing biomechanics when performing landing motions. These alterations may potentially increase the risk of ACL injury. The purpose of this study was to determine if an unanticipated side-cut affects lower extremity landing biomechanics in females. Eighteen recreational female athletes participated in two blocks of testing: the first block of testing consisted of three acceptable trials of anticipated dominant limb and non-dominant limb 45-degree diagonal cutting after landing, which were performed in a counterbalanced order. The second block of testing consisted of three acceptable trials of unanticipated dominant limb and non-dominant limb diagonal cutting after landing. Data analysis mainly focused on the dominant limb landing biomechanics. Unanticipated side-cut landing, compared (paired t-test, p < 0.05) to the anticipated landings, resulted in less hip abduction and tibial internal rotation angle at initial contact (IC) and a lower maximum ankle inversion angle and a greater maximum knee abduction angle, and knee and hip displacement. Also, greater posterior GRF and a longer time to peak medial GRF were exhibited. These outcomes indicate that athletes may adapt their landing mechanics to land unsafely when encountering an unanticipated event.

When efficacy beliefs affect team attributions: relationships between self- and collective efficacy beliefs and team attributions over time.

BACKGROUND: This study investigated the extent to which efficacy beliefs and perceptions of team performance influenced team causal attributions overtime. METHODS: A total of 258 undergraduate students were assigned to a three or four person team and played three games against three different opponents in a semi-round robin team bowling tournament. RESULTS: Multilevel modelling analyses revealed that individuals' perceptions in team performance were positively associated with internal, stable, and team controllable attributions. Collective efficacy beliefs positively predicted team attributions overtime; whereas, self-efficacy beliefs were a negative predictor of team attributions across the tournament. CONCLUSIONS: The results indicated that individuals' perceptions of their team's success/failure were the stronger determinant of team attributions than their team's winning/losing and, as well as, the efficacy beliefs - team attributions relationships were moderated by time.

The effects of a lateral in-flight perturbation on lower extremity biomechanics during drop landings.

One potential ACL injury situation is due to contact with another person or object during the flight phase, thereby causing the person to land improperly. Conversely, athletes often have flight-phase collisions but do land safely. Therefore, to better understand ACL injury causation and methods by which people typically land safely, the purpose of this study was to determine the effects of an in-flight perturbation on the lower extremity biomechanics displayed by females during typical drop landings. Seventeen collegiate female recreational athletes performed baseline landings, followed by either unexpected laterally-directed perturbation or sham (nonperturbation) drop landings. We compared baseline and perturbation trials using paired-samples t tests (P < .05) and 95% confidence intervals for lower-extremity joint kinematics and kinetics and GRF. The results demonstrated that perturbation landings compared with baseline landings exhibited more extended joint positions of the lower extremity at initial contact; and, during landing, greater magnitudes for knee abduction and hip adduction displacements; peak magnitudes of vertical and medial GRF; and maximum moments of ankle extensors, knee extensors, and adductor and hip adductors. We conclude that a lateral in-flight perturbation leads to abnormal GRF and angular motions and joint moments of the lower extremity.

Does wearing a prophylactic ankle brace during drop landings affect lower extremity kinematics and ground reaction forces?

The objective of the study was to determine if prophylactic ankle bracing worn by females during landings produces abnormal lower extremity mechanics. Angular kinematic and ground reaction force (GRF) data were obtained for 16 athletically experienced females who performed brace and no-brace drop landings. The brace condition displayed reduced in/external rotation and flexion displacements about the ankle and knee joints and increased vertical and mediolateral GRF peak magnitudes and rate of vertical GRF application (paired t test, P < .05). The ankle and knee joints landed in a less plantar flexed and more flexed position, respectively. No significant ab/adduction outcomes may have occurred due to interparticipant variability and/or a lack of brace restriction. Conclusion: During typical landings, this lace-up brace increases vertical GRF, decreases ankle and knee joint displacements of flexion and int/external rotation, but minimally affects ab/adduction displacements.