Clinical gait analysis in older children with autism spectrum disorder.

Individuals with autism spectrum disorder (ASD) often exhibit motor deficits that increase their risk of falls. There is a lack of understanding regarding gait biomechanics demonstrated by older children with ASD. The purpose of the study was to determine differences in gait patterns between older children with ASD and typically developing children. Eleven children with ASD and 11 age- and gender-matched typically developing children were recruited for the study. Participants walked on a force-instrumented treadmill at a constant speed (1.1 â€‹m/s â€‹- â€‹1.2 â€‹m/s) for five minutes (min). Participants performed maximal voluntary contractions to assess their knee muscular strength. Differences between individuals with ASD and matched control participants were examined through paired t-tests with a significance level of p â€‹≤ â€‹0.05. Individuals with ASD demonstrated a smaller knee extensor torque compared to controls (p â€‹= â€‹0.002). Participants with ASD exhibited a shorter stride length (p â€‹= â€‹0.04), a greater cadence (p â€‹= â€‹0.03), and a higher variation in stride width (p â€‹= â€‹0.04) compared to control participants. The individuals with ASD experienced a greater braking ground reaction force (p â€‹= â€‹0.03) during loading response. The results indicate older children with ASD develop a unique gait pattern signified by a reduced stride length, increased cadence, and an increase of variation in stride width. This unique gait pattern may represent a movement strategy used by the individuals with ASD to compensate for the weakness associated with their knee extensor muscles. Individuals with ASD who demonstrate these unique gait deviations may face reduced postural stability and an increased risk of fall-related injuries.

Effects of a soccer-specific vertical jump on lower extremity landing kinematics.

Anterior cruciate ligament (ACL) injury frequently occurs in female soccer athletes during deceleration movements such as landings. In soccer, landings mostly occur following jumping headers. Little research has been done to determine the mechanics that follow and how they compare to standard drop vertical jumps (DVJ). The purpose of this study was to analyze differences in kinematics between the DVJ and the soccer-specific vertical jump (SSVJ) in female soccer athletes to better assess the sport-specific risk for ACL injury. A secondary aim was to compare second landings (L2) to first landings (L1). Eight female recreational soccer athletes performed DVJs and SSVJs initiated from a 31 â€‹cm height. Motion capture was performed during landings and data were analyzed using repeated-measures ANOVA. SSVJs produced less peak hip flexion (p â€‹= â€‹0.03) and less peak knee flexion (p â€‹= â€‹0.002) than DVJs. SSVJs also demonstrated increased ankle plantarflexion at initial contact (IC) than DVJs (p â€‹= â€‹0.005). L2s produced less peak hip (p â€‹= â€‹0.007) and knee flexion (p â€‹= â€‹0.002) than L1s. SSVJs and L2s displayed a more erect landing posture than the DVJs and L1s at the hip and knee, a known ACL risk factor. The significant results between jump styles show that the SSVJ displays mechanics that are different from the DVJ. The SSVJ may be a better sport-specific screening tool for ACL injury mechanisms than the DVJ in soccer athletes as it has a more direct translation to the sport.

Soccer participation is associated with benefits in tibial bone cross-sectional geometry and strength in young women.

BACKGROUND: Soccer has been hypothesized to be an ideal sport to stimulate favorable changes in bone properties due the high-intensity, multidirectional movements performed during play. The purpose of this study was to determine if participation in soccer is associated with enhanced bone properties such as volumetric bone mineral density (vBMD), cross-sectional geometry, and estimated strength in the tibias of young, healthy women. METHODS: Twenty female soccer players (20±1 years) and twenty mass- and height-matched healthy women (21±1 years) participated in this cross-sectional study. Peripheral quantitative computed tomography (XCT 3000; Stratec Medizintechnik, Pforzheim, Germany) was used to assess bone characteristics, including vBMD, cross-sectional moments of inertia (CSMI), and strength/strain index (SSI) at 14%, 38%, and 66% of the tibial length proximal to the distal end plate. One-way multivariate analysis of variances were run to determine the influence of soccer training history on tibial properties. RESULTS: Compared to healthy controls, soccer players had approximately 1.5-3% lower cortical vBMD but 18.5-30% greater CSMI and 16.5-19% greater SSI at the three cross-sectional sites along the tibial diaphysis (all P<0.05). CONCLUSIONS: These results suggest that soccer participation is associated with favorable bone cross-sectional geometry and estimates of bone strength. However, randomized controlled intervention trials are needed to confirm whether soccer participation results in favorable bone adaptations in young, healthy adults.

The effect of landing type on kinematics and kinetics during single-leg landings.

Landing research attempts to simulate sport activities; however, movements performed pre- or post-landing may alter landing mechanics and injury risk. Therefore, this study compared lower extremity biomechanics of single-leg drop landings, drop jump (DJ) and countermovement jump (CMJ) landings as well as sex-related differences. A total of 25 recreational athletes (11 females) performed landings from 80% maximum jump height with impact forces, kinematics and joint moments measured during each landing. Altered kinematic and kinetic variables were revealed when a jump was performed pre- or post-landing. CMJ landings were generally performed with a more extended lower extremity at ground contact, less hip and knee motion in the frontal and transverse planes and larger joint moments compared to other landings (p < 0.01). The DJ landings demonstrated greater joint flexion and large frontal and transverse plane motion, paired with decreased impact forces and joint moments (p < 0.05). Across all landings, males displayed larger impact forces and joint moments (p < 0.01), and females demonstrated frontal plane kinematics associated with increased injury risk (p < 0.05). These findings suggest that activities surrounding the landing directly impact landing mechanics and overall risk. Therefore, matching landing type to sport-specific activities increases the efficacy of assessing injury risk during training or rehabilitation programmes.

A Fraction of Recommended Practices: Implementation of the FIFA 11+ in NCAA Soccer Programs.

Background and Objectives: National Collegiate Athletic Association (NCAA) soccer coaches implement numerous warm-up and flexibility strategies to prepare athletes for training and competition. The Fédération Internationale de Football Association (FIFA) developed the 11+ injury prevention program to reduce non-contact injuries. This study aimed to analyze the level of familiarity with and implementation of the evidence-based FIFA 11+ amongst NCAA Division I (DI) and Division III (DIII) men's and women's soccer coaches. Materials and Methods: NCAA soccer coaches in the United States received an Institutional Review Board-approved survey hyperlink. A total of 240 coaches completed the survey. The respondents represented 47.5% men's and 52.5% women's teams distributed within DI and DIII programs. Descriptive statistics are reported as frequency counts and mean ± standard deviation where applicable. Pearson's chi-square tests were performed to assess potential differences with a significance level set at α < 0.05. Results: The results indicated that approximately 62% of the respondents reported being familiar with the FIFA 11+ program. Of those coaches familiar with the program, 15.0% reported full implementation, 57.5% reported partial implementation, and 27.5% reported no implementation. Chi-square analyses revealed significant differences in FIFA 11+ implementation based upon division level (χ2 = 4.56, p = 0.033) and coaching certification levels (χ2 = 13.11, p = 0.011). Conclusions: This study indicates that there is a gap between FIFA 11+ knowledge and actual implementation. To reduce the risk of non-contact injury, there is a need to educate coaches and athletic trainers on the purpose of the FIFA 11+ program and how to perform the exercises correctly.

The biomechanical effect of warm-up stretching strategies on landing mechanics in female volleyball athletes.

Female volleyball athletes incorporate dynamic and static stretching into a warm-up, with evidence generally supporting dynamic stretching to improve performance. However, the effects of these stretching practices on injury risk during subsequent volleyball manoeuvres have yet to be fully elucidated in the warm-up literature. Three-dimensional kinematic data associated with non-contact, lower extremity injury were recorded on 12 female collegiate club volleyball athletes during unilateral landing tasks on the dominant and non-dominant limb. Participants performed landings as part of a volleyball-simulated manoeuvre prior to and post-dynamic (DWU) and combined dynamic-static (CDS) warm-ups. A significant reduction in non-dominant hip adduction angle was found at 15 min post CDS warm-up (p = 0.016; d = 0.38), however, no other warm-up differences were detected. The non-dominant limb demonstrated greater knee abduction (p = 0.006; d = 0.69) and internal rotation angle (p = 0.004; d = 0.88), suggesting that this limb demonstrates more risky landing patterns that are potentially due to altered trunk positioning upon landing. The results show that the majority of selected landing kinematics are unaffected by additional static stretching to a dynamic warm-up and that the non-dominant limb may be at a higher injury risk in female volleyball athletes.

Effect of downhill running grade on lower extremity loading in female distance runners.

Hill running is often used as a foundational training mechanism to build strength and speed. Distance runners in particular are at an increased likelihood of encountering steep hills during training runs. There is limited research regarding downhill running, and there is no research available on the biomechanics of females specifically during downhill running. The purpose of this study was to quantify the differences in loading when running downhill at different grades compared to a level surface in female distance runners to determine the potential risk for injury. Fifteen female distance runners (age: 23.5 ± 4.9 y), who ran 56.3 ± 20.9 km a week participated in this study. Participants ran on a force-instrumented treadmill at 4.0 m/s for 2 min at 0%, -5%, -10%, -15%, and -20% grades, with 5 min of rest between conditions. Study findings showed increased impact forces (p < 0.001), and increased loading rates (p < 0.001) with increasing downhill grades compared to level. These results indicate a significantly greater risk of overuse injury to the lower extremity with steeper downhill grades. Individuals need to be aware of these risks to plan and implement training programmes that will increase performance while minimising injury risk.

Influences of load carriage and physical activity history on tibia bone strain.

BACKGROUND: Military recruits are often afflicted with stress fractures. The military's strenuous training programs involving load carriage may contribute to the high incidence of tibia stress fractures in the army. The purpose of this study was to assess the influences of incremented load carriage and history of physical activity on tibia bone strain and strain rate during walking. METHODS: Twenty recreational basketball players and 20 recreational runners performed 4 walking tasks while carrying 0 kg, 15 kg, 25 kg, and 35 kg loads, respectively. Tibia bone strain and strain rate were obtained through subject-specific multibody dynamic simulations and finite element analyses. Mixed model repeated-measures analyses of variance were conducted. RESULTS: The mean ± SE of the runners' bone strain (µs) during load carriages (0 kg, 15 kg, 25 kg, and 35 kg) were 658.11 ± 1.61, 804.41 ± 1.96, 924.49 ± 2.23, and 1011.15 ± 2.71, respectively, in compression and 458.33 ± 1.45, 562.11 ± 1.81, 669.82 ± 2.05, and 733.40 ± 2.52, respectively, in tension. For the basketball players, the incremented load carriages resulted in compressive strain of 634.30 ± 1.56, 746.87 ± 1.90, 842.18 ± 2.16, and 958.24 ± 2.63, respectively, and tensile strain of 440.04 ± 1.41, 518.86 ± 1.75, 597.63 ± 1.99, and 700.15 ± 2.47, respectively. A dose-response relationship exists between incremented load carriage and bone strain and strain rate. A history of regular basketball activity could result in reduced bone strain and reduced strain rate. CONCLUSION: Load carriage is a risk factor for tibia stress fracture during basic training. Preventative exercise programs, such as basketball, that involved multidirectional mechanical loading to the tibia bones can be implemented for military recruits before basic training commences.

Anticipatory effects on lower extremity kinetics during a land and cross step maneuver in female volleyball players.

BACKGROUND: Anticipation has been previously shown to affect lower extremity mechanics during both landing and cutting maneuvers. However, little research has been conducted looking at the effects of anticipation on lower body kinetics and kinematics during a land and cross step maneuver, which due to similar kinematics, may elicit injury. The purpose of this study was to investigate competitive female volleyball players and the effect of anticipation on lower extremity mechanics during a landing and subsequent cross stepping maneuver. METHODS: Twelve female, college-level volleyball players performed right and left cross step maneuvers following a landing under anticipated and unanticipated conditions. Kinetics were measured for the ankle, knee and hip of the dominant limb during the landing phase of the land and cross step anticipatory conditions. RESULTS: An interaction effect (anticipation x direction; P=0.001) was observed for vertical ground reaction force (VGRF), in which greater VGRF was found during unanticipated pivoting maneuvers. Additional interaction effects were determined for ankle (P=0.004) and hip (P=0.037) power absorption, in which greater absorption was found during anticipated, push off conditions. Frontal plant knee kinetics revealed a higher-order interaction, as a larger knee adduction moment was shown during anticipated, push off trials (P=0.001). CONCLUSIONS: High risk cross step maneuvers were found during unanticipated and anticipated conditions, as athletes demonstrated movement mechanics that may increase the risk of knee injury when performing movements away from the dominant limb. Consideration should be given to drills familiarizing volleyball players with unanticipated and anticipated changes of direction, as well as improving strength of the lower extremity muscles required to effectively decelerate the body, as both training modalities may minimize injury risk during cross step maneuvers.

The relationships between multiaxial loading history and tibial strains during load carriage.

OBJECTIVES: To determine if a history of exercise involving multiaxial loading, through soccer participation, influences tibial stains during incremented load carriage. DESIGN: Cross-sectional study. METHODS: 20 female soccer players (20±1 yr) and 20 mass- and height-matched healthy women (21±1 yr) participated in walking tasks with 0kg, 10kg, 20kg, and 30kg loads on a force instrumented treadmill at 1.67m/s. Subject-specific tibial CT models were combined with subject-specific musculoskeletal models for forward-dynamic simulations and finite element analyses. Strains from the middle third of the tibial shaft were analyzed. A mixed model repeated measures analysis of variance (ANOVA) and one-way ANOVAs were run with a Bonferroni correction setting significance at 0.0009. RESULTS: Significant differences in tibial characteristics were found among loading conditions and between groups (all p<0.0001). Tensile strains were 19.6%, 22.2%, 44.1%, and 20.7% lower in soccer players at 0kg, 10kg, 20kg, and 30kg of load carriage, respectively. Strain rates were 20.4%, 29.9%, 43.4%, and 18.9% lower, respectively, in soccer players. Lower compressive and shear strain magnitudes and rates were also observed in soccer players, with the only exception at the 30kg loading condition in which controls had 2.4% lower strain magnitudes in compression, on average, compared to soccer players. CONCLUSIONS: A history of activity involving multiaxial loading was associated with generally lower estimated tibial strains during load carriage. Lower strain levels during repetitive physical activity may be protective from stress fracture. These findings suggest that physical training, such as participating in soccer, may be effective for preconditioning prior to entering military or endurance training.

Kinetic Analysis of Unilateral Landings in Female Volleyball Players After a Dynamic and Combined Dynamic-Static Warm-up.

Avedesian, JM, Judge, LW, Wang, H, and Dickin, DC. Kinetic analysis of unilateral landings in female volleyball players after a dynamic and combined dynamic-static warm-up. J Strength Cond Res 33(6): 1524-1533, 2019-A warm-up is an important period before training or competition to prepare an athlete for the physical demands of subsequent activity. Previous research has extensively focused on the effects of warm-up in relation to various jumping performance attributes; however, limited research has examined the biomechanical nature of landings after common warm-up practices. Twelve female, collegiate-level volleyball players performed unilateral landings on the dominant and nondominant limb before and after dynamic warm-ups and combined dynamic-static (CDS) warm-ups. Kinetic variables of interest were measured at the hip and knee during the landing phase of a volleyball-simulated jump-landing maneuver. A significant 3-way interaction (warm-up × limb × time) for peak internal knee adduction moment was observed, as this kinetic parameter significantly increased (p = 0.01; d = 0.79) in the nondominant limb at 1-minute post-CDS warm-up. No other warm-up differences were detected; however, significant main effects of limb were determined for dominant-limb internal hip abduction moment (p < 0.01; d = 1.32), dominant-knee internal rotation moment (p < 0.01; d = 1.88), and nondominant-knee external rotation moment (p < 0.01; d = 1.86), which may be due to altered hip and trunk mechanics during the jump landings. This information provides strength and conditioning professionals with biomechanical information to determine warm-up protocols that reduce the risk of injury in female volleyball athletes.

Energy expenditure and muscular activation patterns through active sitting on compliant surfaces.

PURPOSE: To test the effectiveness of sitting surfaces with varied amounts of stability on muscle activity and energy expenditure. METHODS: Using a within-participants repeated measures design, 11 healthy young-adult females (age = 20.0 ± 1.8 years) were measured using indirect calorimetry to assess energy expenditure, and electromyography to assess muscular activation in trunk and leg musculature under 3 different sitting surfaces: flat-firm surface, air-filled cushion, and a stability ball. Data were analyzed using repeated measures analysis of variance with follow-up pairwise contrasts used to determine the specific effects of sitting surface on muscle activation and energy expenditure. RESULTS: Significantly greater energy expenditure was recorded for the stability ball (p = 0.01) and the cushion (p = 0.03) over the flat surface (10.4% and 9.6% greater, respectively), with no differences between the ball and the cushion. Both the ball and the cushion produced higher tibialis anterior activation over the flat surface (1.09 and 0.63 root-mean-square millivolts (RMSmv), respectively), while the stability ball produced higher soleus activity over both cushion and flat surfaces (3.97 and 4.24 RMSmv, respectively). Additionally, the cushion elicited higher adductor longus activity over the ball and flat surfaces (1.76 and 1.81 RMSmv, respectively), but no trunk musculature differences were revealed. CONCLUSION: Compliant surfaces resulted in higher levels of muscular activation in the lower extremities facilitating increased caloric expenditure. Given the increasing trends in sedentary careers and the increases in obesity, this is an important finding to validate the merits of active sitting facilitating increased caloric expenditure and muscle activation.

Validity of Consumer-Based Physical Activity Monitors for Specific Activity Types.

PURPOSE: Consumer-based physical activity (PA) monitors are popular for individual tracking of PA variables. However, current research has not examined how these monitors track energy expenditure (EE) and steps in distinct activities. This study examined the accuracy of the Fitbits One, Zip, and Flex and Jawbone UP24 for estimating EE and steps for specific activities and activity categories. METHODS: Thirty subjects completed a structured protocol consisting of three sedentary, four household, and four ambulatory/exercise activities. All subjects began by lying on a bed for 10 min; 10 other activities were performed for 5 min each. Indirect calorimetry (COSMED) and researcher-counted steps were criterion measures for EE and step counts, respectively. The Omron HJ-720IT pedometer was used as a comparison of step count accuracy. EE and steps were compared with criterion measures using the Friedman repeated-measures nonparametric test and mean absolute percent error (MAPE). RESULTS: All PA monitors predicted EE within 8% of COSMED for sedentary activity but overestimated EE by 16%-40% during ambulatory activity. All monitors except the Fitbit Flex (within 8% of criterion) underestimated EE by 27%-34% during household activity. EE predictions were accompanied with MAPE >10%. For household activity, the Fitbit Flex estimated steps within 10% of researcher-counted steps; all other monitors underestimated steps by 35%-64%. All monitors estimated steps within 4% of researcher-counted steps and displayed MAPE <10% during ambulatory activity. The Omron underestimated household steps by 74% but was within 1% for ambulatory steps. All monitors severely underestimated EE and steps during cycling. CONCLUSION: Consumer-based PA monitors should be used cautiously for estimating EE, although they provide accurate measures of steps for structured ambulatory activity, similar to validated pedometers.

Load distribution and postural changes in young adults when wearing a traditional backpack versus the BackTpack.

Backpacks lead to poor posture due to the posterior placement of the load, which overtime may contribute to low back pain and musculoskeletal complications. This study examined postural and load distribution differences between a traditional backpack (BP) and a nontraditional backpack (BTP) in a young adult population. Using a 3D motion analysis system, 24 healthy young adults (22.5 ± 2.5 years, 12 male) completed both static stance and walking trials on a treadmill with No Load and with 15% and 25% of their body weight using the two different backpacks. There was a significant difference in trunk angle, head angle, and lower extremity joint mechanics between the backpack and load conditions during walking (p<.05). Notably, relative to the No Load condition, trunk angle decreased approximately 14° while head angle increased approximately 13° for the BP 25% state on average. In contrast, average trunk and head angle differences for the BTP 25% state were approximately 7.5° and 7°, respectively. There was also a significant difference in head angle from pre- to post-walk (p<.05) across backpacks, loads, and time. Taken together, the results indicate that the BTP more closely resembled the participants' natural stance and gait patterns as determined by the No Load condition. The more upright posture supported by the BTP may help reduce characteristics of poor posture and, ideally, help to reduce low back pain while carrying loads.

Combined Effects of Drop Height and Fatigue on Landing Mechanics in Active Females.

Drop height and fatigue have been shown in isolation to affect landing mechanics and increase the risk of sustaining an anterior cruciate ligament injury. The purpose of this study was to identify the combined effects of drop height and fatigue on landing mechanics in recreationally active females. To assess this, 11 healthy, young adult females performed a series of drop jumps from randomized heights before and following a lower extremity fatiguing protocol. Findings for kinematic results demonstrated that hip flexion decreased at initial contact (P = .003) and maximum hip (P = .005) and knee flexion (P = .001) angles increased with increases in drop height. Kinetic results demonstrated that vertical ground reaction forces and joint moments and powers increased as height increased. Ground reaction forces and maximum knee valgus increased from pre- to postfatigue with interactive effects observed in frontal plane hip angle at impact and peak ankle moment. These results confirm the effects of drop height and fatigue and highlighted interactions between these factors. The differential effect of fatigue as a function of drop heights helps to illustrate potentially risky situations that should be addressed in training and injury prevention programs.

The relationship between leg preference and knee mechanics during sidestepping in collegiate female footballers.

This study examined the relationship between leg preference and knee mechanics in females during sidestepping. Three-dimensional data were recorded on 16 female collegiate footballers during a planned 45° sidestep manoeuvre with their preferred and non-preferred kicking leg. Knee kinematics and kinetics during initial contact, weight acceptance, peak push-off, and final push-off phases of sidestepping were analysed in both legs. The preferred leg showed trivial to small increases (ES = 0.19-0.36) in knee flexion angle at initial contact, weight acceptance, and peak push-off, and small increases (ES = 0.21-0.34) in peak power production and peak knee extension velocity. The non-preferred leg showed a trivial increase (ES = 0.10) in knee abduction angle during weight acceptance; small to moderate increases (ES = 0.22-0.64) in knee internal rotation angle at weight acceptance, peak push-off, and final push-off; a small increase (ES = 0.22) in knee abductor moment; and trivial increases (ES = 0.09-0.14) in peak power absorption and peak knee flexion velocity. The results of this study show that differences do exist between the preferred and non-preferred leg in females. The findings of this study will increase the knowledge base of anterior cruciate ligament injury in females and can aid in the design of more appropriate neuromuscular, plyometric, and strength training protocols for injury prevention.

Additive effect of repeated bouts of individualized frequency whole body vibration on postural stability in young adults.

Whole body vibration (WBV) has been shown to improve force and power output as well as flexibility and speed, with improvements suggested to result from reduced electromechanical delays, improved rate of force development, and sensitivity of muscle spindles. Fixed frequency studies on postural control have been somewhat equivocal; however, individualized frequency protocols have shown promising results in other motor tasks. To assess this, 18 healthy young adults experienced three 4-minute WBV sessions with postural control assessed before vibration, after multiple exposures, and during recovery, with altered levels of sensory information available to the participants. Sway velocity, sway path length, and sway area were assessed in each environment. Study findings revealed that stability was impacted following WBV, with more challenging environments eliciting improvements persisting for 20 minutes. When the environment was less challenging, postural stability was impaired; however, the effects dissipated quickly (10-20 min). It was determined that exposure to individualized frequency WBV served to impair postural control when the challenge was low, but resulted in heightened stability when the overall challenge was high and vestibular information was needed for stability.

The influence of incline walking on joint mechanics.

Walking is a popular form of exercise and is associated with many health benefits; however, frontal-plane knee joint loading brought about by a large internal knee-abduction moment and cyclic loading could lead to cartilage degeneration over time. Therefore, knee joint mechanics during an alternative walking exercise needs to be analyzed. The purpose of this study was to examine the lower-extremity joint mechanics in the frontal and sagittal planes during incline walking. Fifteen healthy males walked on a treadmill at five gradients (0%, 5%, 10%, 15%, and 20%) at 1.34m/s, and lower-extremity joint mechanics in the frontal and sagittal planes were quantified. The peak internal knee-abduction moment significantly decreased from the level walking condition at all gradients except 5%. Also, a negative relationship between the internal knee-abduction moment and the treadmill gradient was found to exist in 10% increments (0-10%, 5-15%, and 10-20%). The decrease in the internal knee-abduction moment during incline walking could have positive effects on knee joint health such as potentially reducing cartilage degeneration of the knee joint, reducing pain, and decreasing the rate of development of medial tibiofemoral osteoarthritis. This would be beneficial for a knee surgery patient, obese persons, and older adults who are using incline walking for rehabilitation and exercise protocols. Findings from the current study can provide guidance for the development of rehabilitation and exercise prescriptions incorporating incline walking.

The effects of whole-body vibration on the Wingate test for anaerobic power when applying individualized frequencies.

Recently, individualized frequency (I-Freq) has been introduced with the notion that athletes may elicit a greater reflex response at differing levels (Hz) of vibration. The aim of the study was to evaluate acute whole-body vibration as a feasible intervention to increase power in trained cyclists and evaluate the efficacy of using I-Freq as an alternative to 30Hz, a common frequency seen in the literature. Twelve highly trained, competitive male cyclists (age, 29.9 ± 10.0 years; body height, 175.4 ± 7.8 cm; body mass, 77.3 ± 13.9 kg) participated in the study. A Wingate test for anaerobic power was administered on 3 occasions: following a control of no vibration, 30 Hz, or I-freq. Measures of peak power, average power (AP), and the rate of fatigue were recorded and compared with the vibration conditions using separate repeated measures analysis of variance. Peak power, AP, and the rate of fatigue were not significantly impacted by either the 30 Hz or I-Freq vibration interventions (p > 0.05). Given the trained status of the individuals in this study, the ability to elicit an acute response may have been muted. Future studies should further refine the vibration parameters used and assess changes in untrained or recreationally trained populations.

Lower-extremity muscle activity during aquatic and land treadmill running at the same speeds.

CONTEXT: Muscle activation during aquatic treadmill (ATM) running has not been examined, despite similar investigations for other modes of aquatic locomotion and increased interest in ATM running. OBJECTIVES: The objectives of this study were to compare normalized (percentage of maximal voluntary contraction; %MVC), absolute duration (aDUR), and total (tACT) lower-extremity muscle activity during land treadmill (TM) and ATM running at the same speeds. DESIGN: Exploratory, quasi-experimental, crossover design. SETTING: Athletic training facility. PARTICIPANTS: 12 healthy recreational runners (age = 25.8 ± 5 y, height = 178.4 ± 8.2 cm, mass = 71.5 ± 11.5 kg, running experience = 8.2 ± 5.3 y) volunteered for participation. INTERVENTION: All participants performed TM and ATM running at 174.4, 201.2, and 228.0 m/min while surface electromyographic data were collected from the vastus medialis, rectus femoris, gastrocnemius, tibialis anterior, and biceps femoris. MAIN OUTCOME MEASURES: For each muscle, a 2 × 3 repeated-measures ANOVA was used to analyze the main effects and environment-speed interaction (P ≤ .05) of each dependent variable: %MVC, aDUR, and tACT. RESULTS: Compared with TM, ATM elicited significantly reduced %MVC (-44.0%) but increased aDUR (+213.1%) and tACT (+41.9%) in the vastus medialis, increased %MVC (+48.7%) and aDUR (+128.1%) in the rectus femoris during swing phase, reduced %MVC (-26.9%) and tACT (-40.1%) in the gastrocnemius, increased aDUR (+33.1%) and tACT (+35.7%) in the tibialis anterior, and increased aDUR (+41.3%) and tACT (+29.2%) in the biceps femoris. At faster running speeds, there were significant increases in tibialis anterior %MVC (+8.6-15.2%) and tACT (+12.7-17.0%) and rectus femoris %MVC (12.1-26.6%; swing phase). CONCLUSION: No significant environment-speed interaction effects suggested that observed muscle-activity differences between ATM and TM were due to environmental variation, ie, buoyancy (presumed to decrease %MVC) and drag forces (presumed to increase aDUR and tACT) in the water.