Locomotive Biomechanics Wearing a Simulated Portable Life Support System During Varying Cognitive and Treadmill Grade Conditions

Background: The Portable Life Support System (PLSS) worn by astronauts during Extravehicular Activity (EVA) is contained within a backpack. Due to the inherent mass of the PLSS, astronaut center of mass (COM) is altered during ambulation. Recent studies from our laboratory suggest shifts in the COM of the PLSS have minimal effects on exercising metabolism, although differences were observed in trunk angles during ambulation. During EVA, astronauts continuously perform cognitive tasks (CG). Due to the distractive nature of these tasks, safety may be compromised by altered biomechanics. Purpose: To quantify lower extremity kinematics while walking with a simulated PLSS at variable inclines with and without a cognitive task. Methods: Nine subjects underwent treadmill gait analysis walking at 4.0 mph with a flat grade and a 6% decline wearing a 14.5 Kg. PLSS simulator. Within each treadmill grade condition, 30s of 3D motion capture data were collected as subjects walked while looking at a blank computer screen (CON), then while performing a CG. The CG consisted of identifying odd or even numbers and consonant or vowel letters presented for 0.1s on the computer screen. Kinematic data were obtained at 120 Hz using a motion capture system with a Helen Hayes marker set (Motion Analysis Software). Angle kinematic computations were completed using MatLab. Relevant measurements were compared within / between grade and cognitive conditions using a two-way factorial repeated measures analysis of variance test. Results: No significant differences were observed in scores on cognitive tests during the two grade conditions. Maximal left ankle plantarflexion was significantly greater in CG compared to CON; no other differences were observed between the CG and CON. There was a 2.5o difference in right knee flexion angle during the stance phase between the flat and decline positions (p \u3c 0.001). During the swing phase, grade affected knee flexion by 1.9o (p \u3c 0.002). Change in grade also resulted in differences in right and left hip extension in stance phase by 2.8o (p\u3c0.009) and 4.3o (p\u3c0.022) respectively. Conclusions: The cognitive task administered in this investigation is not adversely affected by ambulation at 4.0 mph regardless of treadmill grade. Furthermore, there were minimal effects on walking kinematics during the cognitive task. Subtle biomechanical differences were observed during the two grade conditions within both cognitive conditions. More research utilizing faster treadmill speeds and varying levels of CG may be necessary to detect possible alterations in biomechanics resulting from cognitive tasks

Effects of Different Lifting Cadences on Ground Reaction Forces during the Squat Exercise

The purpose of this investigation was to determine the effect of different cadences on the ground reaction force (GRF(sub R)) during the squat exercise. It is known that squats performed with greater acceleration will produce greater inertial forces; however, it is not well understood how different squat cadences affect GRF(sub R). It was hypothesized that faster squat cadences will result in greater peak GRF(sub R). METHODS: Six male subjects (30.8+/-4.4 y, 179.5+/-8.9 cm, 88.8+/-13.3 kg) with previous squat experience performed three sets of three squats using three different cadences (FC = 1 sec descent/1 sec ascent; MC = 3 sec descent/1 sec ascent; SC = 4 sec descent/2 sec ascent) with barbell mass equal to body mass. Ground reaction force was used to calculate inertial force trajectories of the body plus barbell (FI(sub system)). Forces were normalized to body mass. RESULTS: Peak GRF(sub R) and peak FI(sub system) were significantly higher in FC squats compared to MC (p=0.0002) and SC (p=0.0002). Range of GRF(sub R) and FI(sub system) were also significantly higher in FC compared to MC (p<0.05), and MC were significantly higher than SC (p<0.05). DISCUSSION: Faster squat cadences result in significantly greater peak GRF(sub R) due to the inertia of the system. GRF(sub R) was more dependent upon decent cadence than on ascent cadence. PRACTICAL APPLICATION: This study demonstrates that faster squat cadences produce greater ground reaction forces. Therefore, the use of faster squat cadences might enhance strength and power adaptations to long-term resistance exercise training. Key Words: velocity, weight training, resistive exercis

Isokinetic Knee Strength is Associated with Knee Landing Kinematics during Double-leg Vertical and Depth Jumps

Muscular deficiencies, imbalances, or incorrect mechanics in jumping and landing may result in significant knee ligament strain and increased risk for injury in athletes. PURPOSE: This study aimed to identify possible associations between isokinetic knee flexion and extension strength and peak knee flexion and knee adduction landing angles during multiple jumping tasks. We hypothesized that males and females with greater quadriceps and hamstrings strength would land with greater peak knee flexion and less knee adduction. METHODS: After signing informed consent or adolescent assent forms approved by the committee for the protection of human subjects, eighteen participants (8 female; 10 male) volunteered for this project (24.4+8.7 y; 68.3+18.3 kg; 166.5+15.3 cm).The testing session began with anthropometric measurements of the subjects’ height, weight, and lean body mass. Following a standardized cycle warm-up, participants were outfitted with a lower-body marker set and 3D motion capture data were collected during two countermovement vertical jumps (CMVJ) and depth jumps from a small, 30-cm box (SBDJ) and large, 46-cm box (LBDJ). Isokinetic knee flexion-extension peak torques were then collected at 60˚/sec and 240˚/sec. Pearson correlation coefficients were computed between the peak flexion-extension torques at each angular velocity and peak right knee flexion and adduction landing angles. Alpha was set at a critical level of

Preliminary Analysis of the Feasibility and Effectiveness of Whole Body Vibration as a Therapeutic Intervention in a Skilled Nursing Facility

Skeletal muscle sarcopenia results in loss of strength, power and functional capabilities leading to decreased independence and an increased reliance on the healthcare system. Exercise is an effective countermeasure to age related loss of muscle, but may be difficult in elderly patients with complex functional limitations. Whole body vibration (WBV) is a novel tool used to stimulate the neuromuscular system; research indicates it may improve strength, power, and balance in many populations. Purpose: The purposes of this study were to determine if WBV training is feasible in a skilled nursing facility and if standard of care (SOC) with augmented WBV training improves physical function in patients compared to SOC alone. Methods: A prospective cohort design was used to accomplish the study objectives. Twelve patients (10 females; 2 males) who were residents at a skilled nursing facility consented to the study protocol and were divided into two groups. Group 1 (CON; 73.8 ± 5.7 y; 165.0 ± 0.03 cm; 77.5 ± 11.6kg) underwent SOC therapy intervention including progressive balance, strength, and range of motion exercises. Group 2 (VIB; 74.1 ± 2.3y; 169.0 ± 0.04cm; 70.5 ± 4.3kg) underwent a similar physical therapy intervention but also completed progressive WBV treatment on a symmetrically vibrating plate (2mm; 25-35 Hz). Patients completed clinical tests of physical function before and after the 23 ± 2.3 day intervention. Physical function tests included timed up-and-go (TUG) tests from a 40cm chair and a Berg balance assessment (BBA). Additionally, manual muscle tests were completed using a hand-held dynamometer for hip flexion (HF), hip abduction (HA), knee extension (KE), knee flexion (KF), plantar flexion (PF), and dorsi-flexion (DF). Student’s t-tests were used to compare the difference scores pre- and post-intervention; alpha was set at p\u3c0.05 to determine statistical significance. Results: No adverse effects were documented in either group throughout the study. Mean physical function improved in all tested variables for both groups. However, no between group differences (CON vs. VIB) were observed in BBA (p=0.52), TUG (p=0.07), HF (p=0.80), HA (p=0.47), KE (p=0.73), KF (p=0.97), PF (p=0.59), and DF (p=0.83). Conclusions: Use of WBV as an adjunct exercise intervention in a skilled nursing facility was feasible and safe in this small sample. Although no between group differences were evident, a larger sample is needed to definitively accept or reject the hypothesis. Moreover, systematic research is needed to develop precise protocols to effectively and efficiently utilize WBV in hospitalized elders

Time-Trend Comparison of NFL Combine Peformance from 2000-2009

The National Football League (NFL) combine is a final opportunity for collegiate seniors to showcase physical talent to NFL personnel responsible for draft decisions. Potential draftees complete tests of speed, agility, and power; the results of these tests are distributed to all NFL teams. Due to the importance of combine performance to draft order and corresponding financial incentives, training facilities now specialize in teaching technical strategies to improve combine scoring performance. Many athletes now participate in combine preparation programs which may have resulted in increased performance of recent cohorts. Purpose: To determine if NFL combine performances in the 40-yard sprint, pro agility, vertical and broad jumps have improved from 2000-2009 and if the improvements varied by position. Methods: Combine data were obtained from publically available sources previously used for publication. Data included 1904 football players participating in the combine during the following years: 2000 (n=190), 2001 (n=159), 2002 (n=169), 2003 (n=175), 2004 (n=177), 2005 (n=200), 2006 (n=215), 2007 (n=205), 2008 (n=200), 2009 (n=214). Each player completed the following tests: body mass determination (BM), 40-yard sprint (SP), pro-agility (AG), vertical jump (VJ), and broad jump (BR). Peak power (PP) was calculated using Sayers equation. Based upon collegiate positions, players were divided into 3 groups: Skill Players (n =833), Big Skill Players (n=391), and Lineman (n=680). A two-factor ANOVA (draft-year x position) was completed on each dependent variable. For brevity, only main effects and interactions are reported. Alpha was set at p\u3c0.05 prior to analysis. Results: Body mass did not vary by draft-year (p=0.94) but there was a significant main effect for position (p\u3c0.001). Significant main effects were detected for draft-year (p\u3c0.001) and position (p\u3c0.001) for SP. An interaction effect was present for draft-year by position for AG. Significant main effects were evident for draft-year (p\u3c0.001) and position (p\u3c0.001) for VJ. BR scores varied by draft-year (p\u3c0.001) and position (p\u3c0.001). Significant main effects were identified for power by draft-year (p\u3c0.001) and position (p\u3c0.001). No interaction effects were present for BM, SP, VJ, BJ, and Power. Conclusion: Visual trend analysis suggests there was a systematic improvement in SP and BR during the past 10 years. These improvements do not differ by position grouping. Variations in AG, VJ and power by draft-year were not systematic and likely reflect normal variation in draft cohort talent. Further research is needed to determine if players participating in combine preparation programs score higher than athletes who do not

Reliability of Bell’s Test Conducted with Virtual Reality

Cancellation tasks are commonly used assessment tools to detect unilateral neglect. Bell’s Test, one of the most commonly administered cancellation tasks, requires individuals to quickly and accurately identify “bells” randomly placed in an array of symbols. The reliability of Bells Test conducted with a paper and pencil is well established. A newly developed, commercial software application, allows Bell’s Test to be administered in fully immersive virtual reality environment. PURPOSE: The purpose of this study was to measure the reliability of the Bell’s Test using a virtual reality (VR) system and to establish the level of agreement between the pen-paper and VR administration. METHODS: Fourteen apparently healthy individuals between the age of 24 – 73y volunteered (47.9±20.7y; 166.0±5.2cm; 77.5±16.3kg). Subjects were excluded if they had a history of concussion or had perceptual or visual deficits. Participants completed Bell’s Test a total of four times. The first time, it was completed with a pen-paper (PP). Then, participants completed an initial assessment in VR (VRbase); the same test was administered again in VR one-hour (PostVR1hr) and one-week (PostVR1wk) post baseline. Realization time, total time, and the number of errors committed in the right and left field of view were recorded. Cronbach’s alpha was computed on realization and total time in all VR conditions. Additionally, an ANOVA with repeated measures was used to determine differences in PP, VRbase, PostVR1HR, and PostVR1Wk. The Holms-Sidak method was used to identify pairwise differences. Alpha was set at pa priori. RESULTS: Reliability for realization time for the Bell’s test conducted in VR was acceptable (α=0.79). There was, however, a significant difference between trials (F=6.65; p=0.013). VRbase (29.25±8.11s) was significantly different than PostVR1HR (15.52±4.30; p=0.006). and VRpost1wk (21.24±5.89s; p=0.01). Additionally, PP realization time (15.31±4.25s) was significantly different than PostVR1HR (p=0.02) and PostVR1WK (p=0.03). Reliability for total time for the Bell’s test conducted in VR was good. (α=0.82). There was not a significant difference between the trials (F=4.34; p=0.06) for VRbase(24.1±6.7s), PostVR1HR (45.44±12.6) or VRpost1wk(p=0.06). However, there was a significant difference found in PPtotal time taken and VR1wk with the (p=0.03). The average number of left side omitted bells was 0.50±0.65; 0.07±0.26; 0.07±0.26; 0.14±0.36 for PP, VRbase, Post VR1HR, and PostVR1WK; respectively. The number of bells omitted on the right side was 0.50±0.85, 0.21±0.57, 0.14±0.36, for 0.14±0.36 for PP, VRbase, PostVR1HR, and PostVR1WK; respectively. CONCLUSION: These data indicate that the reliability of the Bell’s Test for the realization time is acceptable, and the total time reliability was good in the virtual reality system. Healthy individuals performing the Bell’s Test in VR show slight improvements one hour after baseline, but there was no difference after one week. More data are needed within different age groups to determine reliability in young and older individuals. Additionally, future studies are required to determine the reliability of Bell’s Test in VR for individuals suffering from neurological injuries or diseases

Timed Up-And-Go Scores are Associated with Balance but not Lower-Extremity Force Production in Elderly Skilled Nursing Facility Patients

Aging is associated with numerous deleterious muscular, skeletal, and neurologic adaptations that may result in functional performance decrements. These decrements are accelerated during periods of unplanned physical inactivity (e.g. hospitalization). Reductions in gait velocity are well documented in the elderly and may result from fear of falling, poor balance, or inability to accelerate because of reduced ground reaction force capabilities. Purpose: To determine if timed up-and-go scores were related to balance or lower extremity force production in skilled nursing facility patients. Methods: Data were collected on 40 patients (77.1±1.4y; 164.2±1.7cm; 75.3±3.3 kg) in an inpatient skilled nursing facility. The 15 males and 25 female patients had a mini mental exam score of \u3e20, and provided informed consent. Each patient completed a timed up-and-go (TUG) test where they stood from a 40cm chair and walked 3 meters before circling a cone and returning to the chair. Total time from the initiation of movement until patients regained the seated position was recorded and used for analysis. The Berg Balance Test was also completed by each patient; only composite scores were used for comparison. Manual muscle tests were completed on the hip, knee, and ankle using a hand-held dynamometer that provided isometric peak force. Isometric force tests were completed for hip flexion (HF), hip abduction (HA), knee extension (KE), knee flexion (KF), plantar flexion (PF), and dorsi-flexion (DF). Pearson’s correlation coefficients were calculated between TUG and Berg composite score and isometric force production at each joint. A multiple regression model was determined using backward elimination. For each comparison, an alpha of p\u3c0.05 was used to determine statistical significance. Results: Independently, TUG times were significantly associated with Berg (r=-0.61; p \u3c0.001), but not age (r=0.24), height (r=0.22), weight (r=0.00), or force production in HF (r=-0.04), HA (r=0.06), KE (r=0.07), KF (r=0.07), DF (r=0.07), or PF (r=-0.11). The final multiple regression model derived via backward elimination explained 53% of the variance in TUG (r=-0.74) and included Berg (p\u3c0.001), HA (p=0.001) and KF (p=0.02) scores. Conclusions: These data suggest that decrements in gait performance with an agility component (TUG) are associated with balance, but poorly associated with single-joint measurements of lower extremity force production. Experimental studies are needed to determine if therapeutic interventions improving balance result in improved gait performance or if multi-joint force production tests better predict gait velocity

Exercising Metabolic, Ventilatory, and Cardiovascular Responses to Isometric Whole Body Vibration Exercise

Purpose: To determine if metabolic, ventilatory, or cardiovascular response to isometric squats with or without external load was enhanced by the addition of a whole body vibration (WBV). Methods: Fifteen subjects (28.4±6.5y; 173.7±8.6 cm; 75.5±20.8 kg) underwent four exercise sessions with three days’ rest between sessions. The sample included 7 males and 8 females. Subject performed 10-sets of one-minute isometrics squats with 45 degrees of knee flexion standing on a WBV platform under four conditions: Unloaded, Unloaded Vibration, Loaded, and Loaded Vibration. Each condition was performed on a separate day; the session order was presented at random. One-minute recovery was given between sets. During the vibration conditions, the plate vibrated at 4mm peak-to-peak displacement and 30Hz. Loaded sessions were performed with a barbell equal to 30% body weight across the subjects shoulder. Oxygen consumption (VO2) and ventilation (VE) were measured using a metabolic cart and heart rate was obtained using polar chest straps. A 2x2 ANOVA was used to evaluate main effects for vibration (vibration vs. no vibration), load (loaded vs. unloaded), and interactions. Results: There were significant vibration (p = 0.02) and load (p = 0.003) main effects for VO2. VO2 during vibration (9.2±3.3 mL.kg-1.min-1) was significantly greater than no vibration (7.9±1.2 mL.kg-1.min-1); VO2 was also greater during the loaded (9.6 ± 3.1 mL . kg-1 . min-1) condition compared to unloaded (7.5±1.1 mL.kg-1.min-1). There were significant vibration (p=0.01) and load (p=0.01) main effects for VE. VE during vibration (20.8±10.0 L.min-1) was greater than no vibration (17.8±4.8 L.min-1); VE was greater during loaded (21.5±9.4 L.min-1) conditions compared to unloaded (17.7±5.5 L.min-1). There were significant vibration (p=0.02) and load (p=0.008) main effects for HR. HR during vibration (97.0±20.3 beats . min-1) was greater than no vibration (86.8 ± 25.7 beats . min-1); HR was also greater during loaded (101.3±20.8 beats . min-1) conditions compared to unloaded (90.8±12.6 beats.min-1). No interaction effects were detected for VO2 (p= 0.16), VE (p=0.14), or HR (p=0.84). Conclusion: Significant differences were observed in VO2, VE, and HR while exercising with WBV. Differences were similar across loaded and unloaded conditions. It is unclear if these small differences would be sufficient to induce enhanced long-term training adaptations. Future research should investigate similar physiological responses during dynamic exercise with a range of loads. Further, research is also needed to determine if these responses are enhanced or diminished by the amplitude, frequency, or duration of the vibration stimulus

Speed and Agility Prediction Models in High School Football Players

Background: Optimal relationships between speed, agility, power and body mass are essential in American football. An increase in body mass, theoretically, reduces acceleration (Newton’s 2nd Law). However, an increase in lean body mass may enhance overall force or power generating potential and momentum of an athlete. Body mass, height, and vertical jump height are routinely measured, easily obtainable, and may be used as predictors of speed and agility. Purpose: To determine associations between height, vertical jump height, and body mass to speed and agility in high school football players. Methods: Data were collected on 1261 male football players (16.4±0.9yrs, 179.7±6.9cm, 87.5±18.4kg) at a regional football combine. In successive order, each athlete completed the following tests: height (HT; cm), body mass (BM; kg), 40-yard sprint (SP; s), pro-agility (AG; s), and vertical jump (VJ; cm). The data were collected after a self selected warm-up and athletes were provided three trials on performance drills. HT was measured using a standard stadiometer and BM using a calibrated scale. SP and AG times were measured with hand held stop watches. Finally, a contact mat was used to measure flight time during a countermovement VJ; subsequently VJ height was calculated from flight time using freely falling body equations. Model prediction equations for SP and AG were generated using SigmaStat statistical software package. For each equation, HT, BM, and VJ were set as predictor variables. Non-significant variables were eliminated from the model with an alpha level of p \u3c 0.05. Results: VJ (R=-0.73), BM (R= 0.67), and HT (R = 0.17), were all significant predictors of SP. The combined regression model SP(s) = 6.60561–0.0217VJ+0.00753BM– 0.00438HT explains 73% of the variance in forty yard sprint time (R=0.086; SEE =0.20). HT (R=0.08), BM (R=0.44), and VJ (-0.62) were significantly correlated with AG and were included in the combined regression model: AG(s) = 6.479-0.00437HT+0.00394BM-0.0180VJ (R=0.40; SEE=0.304). Conclusions: HT, VJ, and BM are strong predictors of linear speed. American football players may be able to increase speed by engaging in exercise programs that reduce body mass and improve vertical ground reaction force production. However, these data suggest that HT, BM, and VJ are not as strong of predictors of agility. Future research should address associations between other potential testing constructs and agility in American football players

Association Between Anthropometrics, Vertical Jump and Broad Jump to Pure and Transitional Acceleration in Junior College Baseball Players

Sprint acceleration is a key physical attribute in baseball players that can be characterized by two phases: pure (PURE) and transitional (TRANS) acceleration. In a linear sprint, PURE occurs from the initiation of movement to approximately 15-meters; TRANS acceleration occurs from approximately 15-meters until an athlete reaches top velocity. Since baseball fields are clearly marked at 13.7m (foul-line) and 27.4m (1st base), acceleration can be determined in a sports-specific environment and these data may be helpful in characterizing player success. Purpose The purpose of this study was to determine the relationship between anthropometrics, vertical, and broad jump ability to PURE and TRANS acceleration of junior college baseball players sprinting to first-base. Methods: Nineteen male junior college baseball players (19.6 ± 2.2y; 181.2 ± 6.9cm; 80.6 ± 11.7kg) volunteered as subjects. They performed tests of physical performance on three days, separated by one week. Initially, subject height and body mass (BM) were determined using a standard equipment. Percent fat (%Fat) was measured using skinfold calipers and a three-site equation. On a separate day, countermovement vertical jumps were performed on a force plate set to sample at 400 Hz. Vertical jump height (VJ), peak force (PF), peak power (PP), and relative power (PP rel) were determined from these data. Broad jump (BJ) distance was measured using a marked court and tape measure. During a third testing day, subjects performed linear sprints from the batter’s box to first-base. Time was recorded at the foul-line and first-base using hand-held stop watches. Acceleration was computed between the two 13.7 meter intervals to first-base: home-plate to the foul-line (PURE) and foul-line to first-base (TRANS). Pearson’s r were calculated between PURE and TRANS and the anthropometric and performance data. Alpha was set a p \u3c 0.05 which equated to r = 0.44 for df = 18. Results: Of the tested variables, PURE was only associated with %Fat (r = -0.50), TRANS was significantly correlated with %Fat (r = -0.61), VJ (r = -0.50), and PP rel (r \=-0.51). Conclusion: These preliminary data indicate a primary determinant of pure acceleration to first-base is %Fat. VJ and PP relative to body mass are also associated with acceleration from the foul-line to first-base. Interesting, body mass was not related to acceleration in either phase. Therefore, strength and conditioning programs that reduce body fat and develop increased peak vertical power capabilities may be helpful in improving overall acceleration to first-base