Propulsive Phase Research Articles

Energy analysis of gait in patients with down syndrome

Backgroundthe primary aim of this study is to analyse the energy parameters of patients with Down syndrome compared to a control group and secondly to verify whether the sport activity leads to differences in energy expenditure. Methods3 groups of subjects were identified: 8 healthy subjects and 147 subjects with Down syndrome, of whom 14 played sports at least once a week. An energy index was calculated, given by the ratio between potential and kinetic energy. Next, kinetic ad potential energy parameters were extrapolated at 60% of the gait cycle (propulsion phase). FindingsDown syndrome group was compared with the control group and emerged that the energy index was higher in the first one. No changes were found between Down syndrome and Down syndrome Sport groups. The analysis of the energy parameters showed that all parameters, except the medio-lateral kinetic energy, were higher in the control than in the Down syndrome groups. The potential energy, medio-lateral kinetic energy, and vertical were higher in the Down syndrome Sport group than in the Down syndrome group. The kinetic energy and the mean velocity were higher in the control group than in Down syndrome Sport group while the medio-lateral kinetic energy was lower. Interpretationsport modified the parameter of potential energy but not that of kinetic energy, which continued to be different compared to the healthy group and increased the oscillations in the medio-lateral plane, which were double compared to Down syndrome group. The increase in potential energy, found to be almost equal to that of control group, indicates an increase in vertical oscillations. This could be because subjects who practise sports have stronger muscles that allow a greater push-off ability, which therefore increases their potential energy.

Effect of power-assistance on upper limb biomechanical and physiological variables during a 6-minute, manual wheelchair propulsion test: a randomised, cross-over study

Purpose Use of a power-assistance wheelchair could reduce the risk of musculoskeletal disorders (MSDs), however, a comprehensive biomechanical evaluation of these systems has not been carried out. This study aimed to evaluate and compare biomechanical UL propulsion variables, and physiological exercise-related variables during the use of a wheelchair with rear drive power assist device (RD-PAD) and a standard manual wheelchair (MW). Materials and methods Twenty-two adults with spinal cord injury were recruited. RD-PAD (SmartDrive system) was fitted to their own MW. An instrumented wheel was used to measure handrim forces, and gas exchange and heart rate were monitored. Participants performed repeated out and back runs for 6 min on a straight outdoor course. Results Distance covered was significantly greater with the RD-PAD (538 ± 104 m versus 470 ± 124 m). Peak mechanical effort during the propulsion phase was significantly lower with the RD-PAD (p < 0.001). Heart rate, metabolic equivalent of task (MET), tidal volume, minute volume, oxygen consumption, and peak oxygen consumption were all significantly lower with the RD-PAD (p < 0.001). Conclusions The results showed that use of RD-PAD increased the distance covered by MW users and reduced the energy costs of propulsion. The biomechanical results indirectly suggest that RD-PAD may reduce the risk of MSD. Implications for Rehabilitation Using the SmartDrive system as propulsion assistance increases the travel autonomy. The SmartDrive system reduces the biomechanical constraints propelling the wheelchair on a slope and low slope. SmartDrive the system reduces the physiological solicitation related to the propulsion of wheelchair.

Effects of Leg Stiffness Regulated by Different Landing Styles on Vertical Drop Jump Performance.

The purpose of this study was to investigate the effects of stiffness regulated by landing styles on drop jump performance. Twenty-four male lacrosse athletes performed drop jumps with stiff (ST), self-selected (SS), and soft (SF) landing from a 0.42 m box. Leg stiffness, ground contact time, depth, jump height, maximum ground reaction force (GRF), GRF at the start of the propulsive phase, mean power, peak power, and the reactive strength index (RSI) were calculated. The results showed that jump height and the RSI had strong correlations to power production in all drop jump styles. Power would be a key factor to overall athletic performance. Repeated measures ANOVA showed significant differences (p < 0.05) in all variables among the three styles. Drop jumps with SS landing had comparable jump height to drop jumps with SF landing and power output to drop jumps with ST landing. Drop jumps with ST landing had significantly lower jump height, but higher GRF, power, and the RSI compared to drop jumps with SF landing. In drop jump testing, drop jumps with SS landing should be used if power and jump height were the major concerns; if the RSI was the major concern, drop jumps with ST landing should be used. Training with drop jumps, one of the main objectives should be increasing power output due to its significant correlation to jump height and the RSI in all conditions.

Comparison Of Lower Extremity Joint Coordination Between Limbs In Individuals With ACL Reconstruction During Landing

Individuals with anterior cruciate ligament reconstruction (ACLR) display smaller dorsiflexion angles (DFA) and knee flexion angles (KFA) during the landing and propulsive phases of jumping in their injured compared with their uninjured limb. Kinematic differences may be due to different sagittal plane ankle and knee joint coordination strategies that influence force attenuation and propulsion. PURPOSE: To compare peak DFA and KFA during landing and coordination pattern frequencies during the landing and propulsion phases of a drop vertical jump between the injured and uninjured limb of individuals with ACLR. METHODS: 15 females and 14 males with unilateral ACLR performed a drop vertical jump from a 30 cm box. Peak DFA and KFA were compared using paired t-tests. A modified vector coding technique and binning analysis were used to compare coordination patterns between sagittal plane DFA and KFA using Wilcoxon signed rank tests. RESULTS: The peak DFA was lower in the injured (121.07 ± 5.27°) compared with the uninjured (123.44 ± 4.70°) limb (Mean Difference: -2.37 [95%CI: -3.81, -.94], p = .002). The peak KFA was not different between the injured (-102.69 ± 14.78°) and uninjured (-103.77 ± 13.59°) limbs (Mean Difference: 1.08 [95%CI: -.66, 2.81], p = .215). The injured limb had more anti-phase (Z = -2.30, p = .022) and less exclusive knee flexion (KF) (Z = -2.11, p = .035) motion during landing than the uninjured limb. In-phase (Z = -.42, p = .676) and exclusive dorsiflexion (DF) (Z = -1.42, p = .157) motion were not different between the injured and uninjured limbs during landing. Anti-phase (Z = -1.32, p = .188), in-phase (z = -.69, p = .49), exclusive knee extension (Z = -1.85, p = .064), and exclusive plantarflexion (Z = -1.95, p = .052) motion were not different between limbs during propulsion. CONCLUSIONS: The injured limb had a smaller peak DFA, more simultaneous DF and KF, and less exclusive KF compared with the uninjured limb during landing. Individuals with ACLR may restrict peak DF in their injured limb during landing to limit isolated knee flexion as a protective mechanism to prevent anterior knee motion. More simultaneous DF and KF may be utilized to reduce the amount of force attenuation required from isolated KF. However, utilizing such a strategy for force attenuation may be perilous since the injured limb lands with less peak DF.

Analysis of the Propulsion Phase of Water Rockets Using Smartphone Sensors and Video Analysis

Water rockets can be used in a variety of ways, from schools to planetariums, with very young kids or adults. We propose here simple forms to work with water rockets, going one step further than a simple launch. A smartphone can be used to film the launch and analyze its motion with video analysis or it can even be attached to the rocket, using its acceleration sensor. We present both experimental techniques, theory, and a discussion about the propelling phase of the rocket’s motion. The results show amazing features that are frequently neglected when discussing parabolic motion.

Phase-Specific Force And Time Metrics During Vertical Hopping In Chronic Ankle Instability

Single limb hopping tests are used to identify motor-behavioral impairments of the lower limb associated with chronic ankle instability (CAI). Impairments are often presumed by the homogeneity of CAI cohorts with aggregate group comparisons and limited by performance-based metrics. PURPOSE: To compare phase-specific force and time metrics during single limb vertical hopping in participants with and without CAI with single-subject analyses to reveal patient-specific movement adaptations. METHODS: Individuals with CAI (n = 25; 13 M, 12F; age = 24 ± 3 y; height = 168.3 ± 12.9 cm; mass = 72.2 ± 15.2 kg) and matched controls (CON) (n = 25; 13 M, 12F; age = 24 ± 4 y; height = 172.5 ± 6.1 cm; mass = 70.8 ± 9.7 kg) completed 3 trials of 5 consecutive single limb vertical hops on a force platform on the affected and preferred limb, respectively. Eccentric and concentric phases were identified for each vertical hop from ground reaction force data and the middle 3 hops were analyzed. Peak vertical force (PVF), time to peak vertical force (TTP), vertical impulse (VI), and phase time (PT) were obtained for each phase. Groups were compared with an unpaired t-test. The Model Statistic procedure was used to test for CAI individual differences with an aggregate CON mean. RESULTS: Concentric PT (p = .041; CAI: 0.23 ± 0.09 s; CON: 0.19 ± 0.0 s; d = 0.53) and TTP (p = .020; CAI: 0.08 ± 0.19 s; CON: 0.03 ± 0.02; d = 0.71) were longer in CAI. While not significant (p = .066), a moderate effect (d = 0.45) was observed for concentric VI between CAI (3.04 ± 0.56 Ns/kg) and CON (3.40 ± 0.91 Ns/kg). Ten CAI participants exhibited less concentric PVF (CAIrange: 15.16-21.07 N/kg; Mdiff = 4.38 ± 1.99 N/kg; d = 0.80-3.39). Eight CAI participants displayed longer concentric TTP (CAIrange: 0.06 - 0.43 s; Mdiff = 0.11 ± 0.05 s; d = 1.58 - 8.03) and longer PT (CAIrange: 0.22 - 0.56 s; Mdiff = 0.15 ± 0.12 s; d = 0.82 - 4.21) compared to CON. Additionally, 10 CAI participants displayed less eccentric TTP (CAIrange: 0.07 - 0.11 s; Mdiff = 0.04 ± 0.02 s; d = 1.00 - 2.91) than CON. CONCLUSION: Individuals with CAI displayed differences during the propulsion phase of repetitive hopping on the affected limb and suggests difficulty transitioning from eccentric to concentric phases. This could reveal a less efficient transfer of lower limb mechanical output from the affected limb during repetitive vertical hopping.

The effect of changes in saddle height on coordination and its variability during pedalling cycle

ABSTRACT Modifications in saddle height affect the range of movement of the lower limb’s joints during pedalling. Although its effect on movement patterns is poorly understood. The purpose of this study was to analyse the acute effects of small changes in bicycle saddle height on pedalling coordination and its variability. Lower extremity kinematic data were collected in random order for ten well-trained cyclists while pedalling at three different saddle heights: preferred, 2% higher and 2% lower than preferred position. A dynamical systems approach was used to quantify the coordination and its variability for selected joint couplings. Modifications in saddle height produced large changes in the frequency of movement patterns, although they were not enough to alter the coordination classification. Lowering the saddle height increased the frequency of the proximal coordinative hip-ankle pattern (F = 11.77, p < .01) and knee-ankle couplings (F = 14.39, p < .01), while decreasing inphase coordination (F > 11.03, p < .01) during the propulsive phase. Pedalling coordination variability was not affected, being greatest during the movement transitions and when the ankle joint was included in the coupling. This study demonstrated that pedalling pattern coordination and coordination variability were generally stable to acute small changes in saddle height in well-trained cyclists.

Comparing biomechanical time series data across countermovement shrug loads

ABSTRACT The effect of load on time-series data has yet to be investigated during weightlifting derivatives. This study compared the effect of load on the force–time and velocity–time curves during the countermovement shrug (CMS). Twenty-nine males performed the CMS at relative loads of 40%, 60%, 80%, 100%, 120%, and 140% one repetition maximum (1RM) power clean (PC). A force plate measured the vertical ground reaction force (VGRF), which was used to calculate the barbell-lifter system velocity. Time-series data were normalized to 100% of the movement duration and assessed via statistical parametric mapping (SPM). SPM analysis showed greater negative velocity at heavier loads early in the unweighting phase (12–38% of the movement), and greater positive velocity at lower loads during the last 16% of the movement. Relative loads of 40% 1RM PC maximised propulsion velocity, whilst 140% 1RM maximized force. At higher loads, the braking and propulsive phases commence at an earlier percentage of the time-normalized movement, and the total absolute durations increase with load. It may be more appropriate to prescribe the CMS during a maximal strength mesocycle given the ability to use supramaximal loads. Future research should assess training at different loads on the effects of performance.

Gait ability on center of pressure excursion using a pressure-sensitive mat in the elderly with ischemic stroke: a case–control study with propensity score matching

Background: Center of pressure (COP) is a useful measure for dynamic balance, which directly represents the ability of weight shift and control of the foot, however, there is no study analyzing COP during whole stance phase in the elderly with acute stroke.Methods: A total of 30 acute ischemic stroke patients (mean age±standard deviation [SD], 75.0±5.6 years; 11 females) and 30 propensity score matched controls (mean age±SD, 72.8±5.9 years; 17 females) using age, sex, and Korean version of Mini-Mental State Examination score were finally included. Participants performed barefoot walking trials on a pressure-sensitive mat until 20 footfalls in each limb were corrected. To evaluate gait function based on COP, mean and coefficient of variance as variability were calculated for 3 types of variables as followings: (1) durations of sub-phases in stance phase, (2) mean locations and displacement ranges of COP, and (3) velocities.Results: Significant difference was observed in many of both mean and variability variables. Especially, stroke patients had an increased duration, posterior location of COP, wide range of mediolateral and anteroposterior displacement range, and slow velocity in foot flat phase belonging to the double limb stance. In variability variables, stroke patients had significantly larger variabilities of COP velocities in all sub-phases except in foot flat phase and late propulsive phase were stood out.Conclusions: The elderly with acute ischemic stroke had inefficiency during double limb stance and reduced functional balance in single limb stance in both sides, implying impaired gait ability on COP excursion in these patients.

Can orthotic wedges change the lower-extremity and multi-segment foot kinematics during gait in people with plantar fasciitis?

BackgroundOrthotic wedges with medial posting of the forefoot and rearfoot have been shown to be effective in controlling excessive foot pronation in people with plantar fasciitis (PF), however the best prescription remains unclear. Research questionThe aim of this study was to determine the biomechanical effects of two designs of orthotic wedges within a shoe on the hip, knee, rearfoot, and forefoot kinematics in individuals with PF. MethodsThirty-five participants with PF were recruited. They were asked to walk under three randomized conditions; shod, shod with orthotic wedges with foot assessment technique 1 (W1), and shod with orthotic wedges from a new assessment technique (W2). Biomechanical outcomes included lower limb and multi-segment foot kinematics in each subphase of the stance gait, including contact phase, midstance phase, and propulsive phase. ResultsCompared with shod, the W1 significantly increased rearfoot dorsiflexion, decreased peak forefoot dorsiflexion, and peak rearfoot eversion during the contact phase. In addition, W1 increased rearfoot inversion, decreased hallux dorsiflexion, and peak hallux dorsiflexion during the propulsive phase. For W2, the wedge significantly decreased peak knee internal rotation, decreased forefoot abduction, peak forefoot dorsiflexion, and peak rearfoot eversion during the contact phase. In addition, W2 increased rearfoot inversion, decreased hallux dorsiflexion, and decreased peak hallux dorsiflexion during the propulsive phase. When comparing W1 and W2, W1 showed greater rearfoot dorsiflexion during the contact phase. SignificanceThese findings suggest that the use of forefoot varus wedges, and the combination of forefoot and rearfoot varus wedges, can change the lower limb kinematics, the multi-segment foot kinematics estimated using markers fixed to the shoe, and the relative length of the plantar fascia which can be associated with a reduction in pain and symptoms during walking.

Electomyographic activities of shoulder muscles during Handwheelchair.Q vs pushrim wheelchair propulsion.

Different mechanisms of force transmission have been developed for the movement of wheelchairs, from the standard pushrim propulsion to the handbike. Contributing to this repertoire, we recently developed a system of propulsion based on a pulley-cable mechanism, the Handwheelchair.Q. In contrast to other propulsion systems, the Handwheelchair.Q requires users to extend the shoulders and flex the elbows to move the wheelchair forward, mimicking the rowing gesture. Whether however our proposed, propulsion system imposes a similar degree of shoulder muscles excitation with respect to the conventional, pushrim system is yet to be addressed. In this study we therefore assess whether the Handwheelchair.Q demands a similar degree and timing of muscle excitation with respect to the pushrim wheelchair, for a given travelled distance. We address this issue by sampling the angular speed of the two wheels and the surface EMGs from ten, shoulder muscles, while seven subjects use the two propulsion systems at constantly low and high speeds, one at a time. As expected, results revealed opposite muscle groups were excited when comparing the two mechanisms for wheelchair propulsion. ANOVA statistics indicated the amplitude of EMGs was greater for shoulder flexors and elbow extensors during the drive phase of pushrim propulsion, with the opposite being observed for the Handwheelchair.Q. Interestingly, from the angular speed we observed a significantly greater average displacement was achieved with the Handwheelchair.Q. Our results support therefore the notion that, with respect to pushrim propulsion, subjects were able to move faster without overloading the shoulder muscle with the Handwheelchair.Q.

Altered countermovement jump force profile and muscle-tendon unit kinematics following combined ballistic training.

Combined heavy‐ and light‐load ballistic training is often employed in high‐performance sport to improve athletic performance and is accompanied by adaptations in muscle architecture. However, little is known about how training affects muscle‐tendon unit (MTU) kinematics during the execution of a sport‐specific skill (e.g., jumping), which could improve our understanding of how training improves athletic performance. The aim of this study was to investigate vastus lateralis (VL) MTU kinematics during a countermovement jump (CMJ) following combined ballistic training. Eighteen young, healthy males completed a 10‐week program consisting of weightlifting derivatives, plyometrics, and ballistic tasks under a range of loads. Ultrasonography of VL and force plate measurements during a CMJ were taken at baseline, mid‐test, and post‐test. The training program improved CMJ height by 11 ± 13%. During the CMJ, VL's MTU and series elastic element (SEE) length changes and velocities increased from baseline to post‐test, but VL's fascicle length change and velocity did not significantly change. It is speculated that altered lower limb coordination and increased force output of the lower limb muscles during the CMJ allowed more energy to be stored within VL's SEE. This may have contributed to enhanced VL MTU work during the propulsion phase and an improved CMJ performance following combined ballistic training.

Improving Ankle Muscle Recruitment via Plantar Pressure Biofeedback during Robot Resisted Gait Training in Cerebral Palsy.

Neurological impairment from stroke or cerebral palsy often presents with diminished ankle plantar flexor function during the propulsive phase of gait. This deficit often results in slow, energy-expensive walking patterns that limit community mobility. Robotic gait training interventions may prove effective in improving functional outcomes, including exoskeleton resistance used to provide targeted neuromuscular recruitment. However, these interventions to date have required regular verbal cues and coaching for proper plantar flexor engagement with resistance, particularly for pediatric applications. In this validation study, we sought to address the need for automating and improving the effectiveness of facilitating user engagement with robotic resistance. Specifically, our main goal was to compare changes in plantar flexor activity between walking with plantar flexor resistance alone vs plantar flexor resistance combined with plantar pressure biofeedback in individuals with cerebral palsy. We recruited 8 ambulatory adolescents with cerebral palsy between the ages of 11-18 years old to participate in this cross-sectional feasibility study. Supporting our hypothesis, we observed a 36 ± 36% and 46 ± 39% increase in mean and peak soleus activity, respectively, between resistance plus biofeedback vs resistance alone (both p < 0.05). Compared to other biofeedback sensing modalities like assessment of muscle activity via surface electrodes, integrating the plantar pressure-based system within the wearable robotic devices minimizes barriers to clinical implementation by reducing cost, complexity, and setup time. With these positive feasibility results, our future work will explore longer-term training effects of ankle resistance combined with plantar pressure biofeedback.

Examining the intrinsic foot muscles’ capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping

BackgroundDuring human locomotion, a sufficiently stiff foot allows the ankle plantar flexors to generate large propulsive powers. Increasing foot stiffness (e.g., via a carbon plate) increases the ankle's external moment arm in relation to the internal moment arm (i.e., increasing gear ratio), reduces plantar flexor muscles’ shortening velocity, and enhances muscle force production. In contrast, when activation of the foot's intrinsic muscles is impaired, there is a reduction in foot and ankle work and metatarsophalangeal joint stiffness. We speculated that the reduced capacity to actively control metatarsophalangeal joint stiffness may impair the gearing function of the foot at the ankle. MethodsWe used a tibial nerve block to examine the direct effects of the intrinsic foot muscles on ankle joint kinetics, in vivo medial gastrocnemius’ musculotendinous dynamics, and ankle gear ratio on 14 participants during maximal vertical jumping. ResultsUnder the nerve block, the internal ankle plantar flexion moment decreased (p = 0.004) alongside a reduction in external moment arm length (p = 0.021) and ankle joint gear ratio (p = 0.049) when compared to the non-blocked condition. Although medial gastrocnemius muscle–tendon unit and fascicle velocity were not different between conditions, the Achilles tendon was shorter during propulsion in the nerve block condition (p < 0.001). ConclusionIn addition to their known role of regulating the energetic function of the foot, our data indicate that the intrinsic foot muscles also act to optimize ankle joint torque production and leverage during the propulsion phase of vertical jumping.

Push-Off Dynamics Reveal Task-Independent Alterations in Athletes Returning to Sport after ACL Reconstruction.

Athletes with an anterior cruciate ligament (ACL) reconstruction (ACLR) show persisting biomechanical and neuromuscular landing alterations. So far, most research focused on the landing phase of dynamic tasks where most ACL injuries occur. This study will assess whether these landing alterations are also present in the propulsion phase, in an attempt to identify generalized movement alterations. Twenty-one athletes with ACLR (cleared by their surgeon and/or physiotherapist for return-to-sport) and twenty-one controls performed five single-leg hop tasks. Propulsion kinematics, kinetics, and muscle activations were compared between legs and between groups. Increased hamstrings activation was found during propulsion when comparing the ACLR limb with both the uninjured limb and the controls. In addition, decreased internal knee extension moments were found in the ACLR limb compared with the uninjured limb. Athletes with ACLR show task-independent alterations that unload the knee during the propulsion phase of single-leg hopping tasks. If longitudinal data deem these alterations to be maladaptive, more emphasis must be placed on their normalization during the propulsion phase, assuming beneficial carryover effects into the landing phase. Normalizing these patterns during rehabilitation may potentially reduce the risk of long-term complications such as reinjuries and posttraumatic osteoarthritis.

Achilles Tendon Mechanical Behavior and Ankle Joint Function at the Walk-to-Run Transition.

Simple SummaryIn this study we investigated the ankle joint functional indexes and the Achilles tendon mechanical behaviour (changes in AT force and power as a function of speed and gait) during walking and running at speeds close to transition speed (about 7.2–7.5 km/h in healthy adults), to better elucidate the mechanical determinants of the walk-to-run transition. Our results indicate that, when walking at speeds faster than the typical transition speed (7.5–8.5 km/h), the Achilles tendon mechanical behavior is impaired: the force acting along its line of action is reduced, as well as its contribution in determining the total mechanical power of the muscle–tendon unit. Moreover, our data suggest that the walk-to-run transition could be partially explained by the need to preserve the spring-like function of the ankle joint (which is indeed lower in walking than in running at speeds > 7.5 km/h).Walking at speeds higher than transition speed is associated with a decrease in the plantar-flexor muscle fibres’ ability to produce force and, potentially, to an impaired behaviour of the muscle–tendon unit (MTU) elastic components. This study aimed to investigate the ankle joint functional indexes and the Achilles tendon mechanical behaviour (changes in AT force and power) to better elucidate the mechanical determinants of the walk-to-run transition. Kinematics, kinetic and ultrasound data of the gastrocnemius medialis (GM) were investigated during overground walking and running at speeds ranging from 5–9 km·h−1. AT and GM MTU force and power were calculated during the propulsive phase; the ankle joint function indexes (damper, strut, spring and motor) were obtained using a combination of kinetic and kinematic data. AT force was larger in running at speeds > 6.5 km/h. The contribution of AT to the total power provided by the GM MTU was significantly larger in running at speeds > 7.5 km/h. The spring and strut indexes of the ankle were significantly larger in running at speeds > 7.5 km/h. These data suggest that the walk-to-run transition could (at least partially) be explained by the need to preserve AT mechanical behaviour and the ankle spring function.

Alterations in shoulder kinematics are associated with shoulder pain during wheelchair propulsion sprints.

The study purpose was to examine the biomechanical characteristics of sports wheelchair propulsion and determine biomechanical associations with shoulder pain in wheelchair athletes. Twenty wheelchair court‐sport athletes (age: 32 ± 11 years old) performed one submaximal propulsion trial in their sports‐specific wheelchair at 1.67 m/s for 3 min and two 10 s sprints on a dual‐roller ergometer. The Performance Corrected Wheelchair User's Shoulder Pain Index (PC‐WUSPI) assessed shoulder pain. During the acceleration phase of wheelchair sprinting, participants propelled with significantly longer push times, larger forces, and thorax flexion range of motion (ROM) than both the maximal velocity phase of sprinting and submaximal propulsion. Participants displayed significantly greater peak glenohumeral abduction and scapular internal rotation during the acceleration phase (20 ± 9° and 45 ± 7°) and maximal velocity phase (14 ± 4° and 44 ± 7°) of sprinting, compared to submaximal propulsion (12 ± 6° and 39 ± 8°). Greater shoulder pain severity was associated with larger glenohumeral abduction ROM (r = 0.59, p = 0.007) and scapular internal rotation ROM (r = 0.53, p = 0.017) during the acceleration phase of wheelchair sprinting, but with lower peak glenohumeral flexion (r = −0.49, p = 0.030), peak abduction (r = −0.48, p = 0.034), and abduction ROM (r = −0.44, p = 0.049) during the maximal velocity phase. Biomechanical characteristics of wheelchair sprinting suggest this activity imposes greater mechanical stress than submaximal propulsion. Kinematic associations with shoulder pain during acceleration are in shoulder orientations linked to a reduced subacromial space, potentially increasing tissue stress.

Unsupervised Clustering Techniques Identify Movement Strategies in the Countermovement Jump Associated With Musculoskeletal Injury Risk During US Marine Corps Officer Candidates School.

Musculoskeletal injuries (MSKI) are a significant burden on the military healthcare system. Movement strategies, genetics, and fitness level have been identified as potential contributors to MSKI risk. Screening measures associated with MSKI risk are emerging, including novel technologies, such as markerless motion capture (mMoCap) and force plates (FP) and allow for field expedient measures in dynamic military settings. The aim of the current study was to evaluate movement strategies (i.e., describe variables) of the countermovement jump (CMJ) in Marine officer candidates (MOCs) via mMoCap and FP technology by clustering variables to create distinct movement strategies associated with MSKI sustained during Officer Candidates School (OCS). 728 MOCs were tested and 668 MOCs (Male MOCs = 547, Female MOCs = 121) were used for analysis. MOCs performed 3 maximal CMJs in a mMoCap space with FP embedded into the system. De-identified MSKI data was acquired from internal OCS reports for those who presented to the OCS Physical Therapy department for MSKI treatment during the 10 weeks of OCS training. Three distinct clusters were formed with variables relating to CMJ kinetics and kinematics from the mMoCap and FPs. Proportions of MOCs with a lower extremity and torso MSKI across clusters were significantly different (p < 0.001), with the high-risk cluster having the highest proportions (30.5%), followed by moderate-risk cluster (22.5%) and low-risk cluster (13.8%). Kinetics, including braking rate of force development (BRFD), braking net impulse and propulsive net impulse, were higher in low-risk cluster compared to the high-risk cluster (p < 0.001). Lesser degrees of flexion and shorter CMJ phase durations (braking phase and propulsive phase) were observed in low-risk cluster compared to both moderate-risk and high-risk clusters. Male MOCs were distributed equally across clusters while female MOCs were primarily distributed in the high-risk cluster. Movement strategies (i.e., clusters), as quantified by mMoCap and FPs, were successfully described with MOCs MSKI risk proportions between clusters. These results provide actionable thresholds of key performance indicators for practitioners to use for screening measures in classifying greater MSKI risk. These tools may add value in creating modifiable strength and conditioning training programs before or during military training.

Intermittent propulsion in largemouth bass, Micropterus salmoides, increases power production at low swimming speeds.

Locomotion dominates animal energy budgets, and selection should favour behaviours that minimize transportation costs. Recent fieldwork has altered our understanding of the preferred modes of locomotion in fishes. For instance, bluegill employ a sustainable intermittent swimming form with 2-3 tail beats alternating with short glides. Volitional swimming studies in the laboratory with bluegill suggest that the propulsive phase reflects a fixed-gear constraint on body-caudal-fin activity. Largemouth bass (Micropterus salmoides) also reportedly display intermittent swimming in the field. We examined swimming by bass in a static tank to quantify the parameters of volitional locomotion, including tailbeat frequency and glide duration, across a range of swimming speeds. We found that tailbeat frequency was not related to speed at low swimming speeds. Instead, speed was a function of glide duration between propulsive events, with glide duration decreasing as speed increased. The propulsive Strouhal number remained within the range that maximizes propulsive efficiency. We used muscle mechanics experiments to simulate power production by muscle operating under intermittent versus steady conditions. Workloop data suggest that intermittent activity allows fish to swim efficiently and avoid the drag-induced greater energetic cost of continuous swimming. The results offer support for a new perspective on fish locomotion: intermittent swimming is crucial to aerobic swimming energetics.

Positive Impulse Phase versus Propulsive Impulse Phase: Correlations between Asymmetry and Countermovement Jump Performance.

The relationship between asymmetry and performance is still undetermined in the literature. Methods of assessing asymmetry have been inconsistent and focused on the analysis of jumping asymmetry. Dual ground reaction forces are prevalent in athlete monitoring, though underutilized in asymmetry research. The purpose of this study was to assess the relationship of countermovement jump (CMJ) impulse asymmetry to performance in collegiate soccer athletes. Male and female athletes were selected from an ongoing athlete research repository database of NCAA D-I soccer athletes. All athletes contributed two maximal effort unweighted (CMJ0) and weighted countermovement jumps (CMJ20) using the mean for calculations. Propulsive phase asymmetry scores (PrPAS) and positive impulse asymmetry scores (PIAS) were calculated to determine the magnitude of asymmetry for each prospective phase. Statistically significant correlations were found between CMJ0 jump height and unweighted PIAS (r = −0.43) in females. Males had statistically significant correlations between CMJ20 jump height and weighted PIAS (r = −0.49). Neither unweighted PrPAS nor weighted PrPAS produced statistically significant correlations (r < 0.26) to their prospective jump heights. When assessing CMJ asymmetry, it is recommended to conduct both weighted and unweighted CMJ testing, utilizing PIAS as the metric to be assessed.