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BACKGROUND: The supplementary motor area (SMA) is implicated in stereotypic multi-limb movements such as walking with arm swing. Gait difficulties in Parkinson's Disease (PD) include reduced arm swing, which is associated with reduced SMA activity.OBJECTIVE: To test whether enhanced arm swing improves Parkinsonian gait and explore the role of the SMA in such an improvement.METHODS: Cortical activity and gait characteristics were assessed by ambulant EEG, accelerometers and video recordings in 27 PD patients with self-reported gait difficulties and 35 healthy participants when walking normally. Within these two groups, 19 PD patients additionally walked with enhanced arm swing and 30 healthy participants walked without arm swing. Power changes across the EEG frequency spectrum were assessed by Event Related Spectral Perturbation analysis of recordings from Fz over the putative SMA and gait analysis was performed.RESULTS: Baseline PD gait, characterized by reduced arm swing among other features, exhibited reduced within-step Event Related Desynchronization (ERD)/Synchronization (ERS) alternation (Fz; 20-50Hz), accompanied by a reduced step length and walking speed. All became similar to normal gait when patients walked with enhanced arm swing. When healthy controls walked without arm swing, their alternating ERD-ERS pattern decreased, mimicking baseline PD gait.CONCLUSION: Enhanced arm swing may serve as a driving force to overcome impaired gait control in PD patients by restoring reduced ERD-ERS alternation over the putative SMA. Accompanied by increased step length and walking speed, this provides a neural underpinning of arm swing as an effective rehabilitation concept for improving Parkinsonian gait.

Background The Hawthorne Effect occurs when participants alter their behavior when they are aware that they are being examined. The effect has been reported in many experiments, including gait analysis, and is considered an important source of bias that might impact both clinical and research results. Cognitive distraction is one potential solution to reducing the Hawthorne effect during gait analysis, but it is challenging in children, and can, in itself, alter gait. This study investigated the carryover effect of an alternative low-immersion avatar-based intervention on gait and subjective feelings in typically developing children. Research Question Will a low-immersion avatar-based intervention change feelings and indicators of temporospatial and kinematic outcomes in children in a laboratory setting, potentially reducing the Hawthorne Effect? Methods Typically developing children aged 5–13 participated in a standard laboratory gait analysis before experiencing a game in which they viewed their motion on monitors around the lab as that of a cartoon avatar in a 3D virtual environment. Following this intervention, standard walking trials were repeated. In addition, participants completed a survey of their feelings about the study both before onset and after completion. Results Thirty-one children participated in the study, 16 females and 15 males, mean aged 9.1 years. Arm swing, proposed as a measure of how relaxed and natural gait was, increased significantly following the intervention, while temporospatial parameters did not. The effect was more pronounced in females and younger children. Participants felt significantly happier, more excited, less scared, and less sad after the intervention. Changes in feelings were not closely associated with changes in gait. Significance This study suggests that gamification may reduce the Hawthorne effect and potentially produce more natural gait in children. The game intervention had a carryover effect, producing changes in gait even after the intervention was removed.

Key points Gait‐related arm swing in humans supports efficient lower limb muscle activation, indicating a neural coupling between the upper and lower limbs during gait.Intermuscular coherence analyses of gait‐related electromyography from upper and lower limbs in 20 healthy participants identified significant coherence in alpha and beta/gamma bands indicating that upper and lower limbs share common subcortical and cortical drivers that coordinate the rhythmic four‐limb gait pattern.Additional directed connectivity analyses revealed that upper limb muscles drive and shape lower limb muscle activity during gait via subcortical and cortical pathways and to a lesser extent vice versa.The results provide a neural underpinning that arm swing may serve as an effective rehabilitation therapy concerning impaired gait in neurological diseases. Abstract Human gait benefits from arm swing, as it enhances efficient lower limb muscle activation in healthy participants as well as patients suffering from neurological impairment. The underlying neuronal mechanisms of such coupling between upper and lower limbs remain poorly understood. The aim of the present study was to examine this coupling by intermuscular coherence analysis during gait. Additionally, directed connectivity analysis of this coupling enabled assessment of whether gait‐related arm swing indeed drives lower limb muscles. To that end, electromyography recordings were obtained from four lower limb muscles and two upper limb muscles bilaterally, during gait, of 20 healthy participants (mean (SD) age 67 (6.8) years). Intermuscular coherence analysis revealed functional coupling between upper and lower limb muscles in the alpha and beta/gamma band during muscle specific periods of the gait cycle. These effects in the alpha and beta/gamma bands indicate involvement of subcortical and cortical sources, respectively, that commonly drive the rhythmic four‐limb gait pattern in an efficiently coordinated fashion. Directed connectivity analysis revealed that upper limb muscles drive and shape lower limb muscle activity during gait via subcortical and cortical pathways and to a lesser extent vice versa. This indicates that gait‐related arm swing reflects the recruitment of neuronal support for optimizing the cyclic movement pattern of the lower limbs. These findings thus provide a neural underpinning for arm swing to potentially serve as an effective rehabilitation therapy concerning impaired gait in neurological diseases., Key points Gait‐related arm swing in humans supports efficient lower limb muscle activation, indicating a neural coupling between the upper and lower limbs during gait.Intermuscular coherence analyses of gait‐related electromyography from upper and lower limbs in 20 healthy participants identified significant coherence in alpha and beta/gamma bands indicating that upper and lower limbs share common subcortical and cortical drivers that coordinate the rhythmic four‐limb gait pattern.Additional directed connectivity analyses revealed that upper limb muscles drive and shape lower limb muscle activity during gait via subcortical and cortical pathways and to a lesser extent vice versa.The results provide a neural underpinning that arm swing may serve as an effective rehabilitation therapy concerning impaired gait in neurological diseases.

BACKGROUND: The supplementary motor area (SMA) is implicated in both motor initiation and stereotypic multi-limb movements such as walking with arm swing. Gait in Parkinson's disease exhibits starting difficulties and reduced arm swing, consistent with reduced SMA activity.OBJECTIVE: We tested whether enhanced arm swing could improve Parkinson gait initiation and assessed whether increased SMA activity during preparation might facilitate such improvement.METHODS: Effects of instructed arm swing on cortical activity, muscle activity and kinematics were assessed by ambulant EEG, EMG, accelerometers and video in 17 Parkinson patients and 19 controls. At baseline, all participants repeatedly started walking after a simple auditory cue. Next, patients started walking at this cue, which now meant starting with enhanced arm swing. EEG changes over the putative SMA and leg motor cortex were assessed by event related spectral perturbation (ERSP) analysis of recordings at Fz and Cz.RESULTS: Over the putative SMA location (Fz), natural PD gait initiation showed enhanced alpha/theta synchronization around the auditory cue, and reduced alpha/beta desynchronization during gait preparation and movement onset, compared to controls. Leg muscle activity in patients was reduced during preparation and movement onset, while the latter was delayed compared to controls. When starting with enhanced arm swing, these group differences virtually disappeared.CONCLUSION: Instructed arm swing improves Parkinson gait initiation. ERSP normalization around the cue indicates that the attributed information may serve as a semi-internal cue, recruiting an internalized motor program to overcome initiation difficulties.

Gillen, ZM, Shoemaker, ME, McKay, BD, Bohannon, NA, Gibson, SM, and Cramer, JT. Influences of the stretch-shortening cycle and arm swing on vertical jump performance in children and adolescents. J Strength Cond Res XX(X): 000-000, 2020-This study compared the influences of the stretch-shortening cycle and arm swing on vertical jump performance during static jumps (SJs), counter-movement jumps (CMJs), and CMJs with arm swing (CMJAs) in young male and female athletes. Twenty-one boys (age = 12.1 ± 1.1 years) and 21 girls (age = 12.1 ± 1.1 years) performed SJs, CMJs, and CMJAs on force plates that sampled at 1 kHz. Measurements included peak force, rate of force development, peak power (PP), eccentric impulse (ECC), concentric impulse (CON), estimated jump height (JH), and changes in PP and JH across vertical jumps. Measurements of growth included age, maturity offset, height, body mass, fat-free mass, and thigh muscle cross-sectional area. Analyses of variance were used to analyze growth measurements across sex, as well as vertical jump outcome measures. Pearson product moment correlation coefficients were used to determine the relationships between changes in PP and JH across vertical jumps and growth measurements. There were differences in PP and JH such that SJ < CMJ < CMJA (p < 0.001), and ECC such that SJ < CMJA < CMJ (p ≤ 0.048). Changes in PP were greater from the SJ to CMJ than CMJ to CMJA (p ≤ 0.001). The change in PP from the SJ to CMJ exhibited moderate-to-high relationships with growth measurements for boys and girls (r = 0.543-0.803). Because young children may not have the skeletal musculature or strength necessary to absorb and reapply large eccentric preloading forces, future studies should consider using the CMJA, rather than the CMJ, to maximize vertical jump performance and minimize ECC. Coaches and practitioners can expect approximately 27-33% greater PP and 15-17% greater estimated JH when an arm swing is included during the CMJ.

Heishman, AD, Daub, BD, Miller, RM, Freitas, EDS, Frantz, BA, and Bemben, MG. Countermovement jump reliability performed with and without an arm swing in NCAA Division 1 intercollegiate basketball players. J Strength Cond Res 34(2): 546-558, 2020-The countermovement jump (CMJ) is routinely used in athlete performance to quantify adaptions to training, as well as monitor neuromuscular readiness and fatigue. However, controversy remains in whether to incorporate an arm swing during the CMJ (CMJ AS) or keep the hands placed on the hips (CMJ NAS). Incorporating the arms provides a higher degree of sport-specificity that may yield improved reliability, especially in skilled jumpers. By contrast, the hands-on-hips approach isolates lower extremity force production and eliminates potential arm-swing variation. Therefore, the purpose of this study was to establish the reliability of CMJ typical (CMJ-TYP), CMJ concentric alternative (CMJ-Conc-ALT), and CMJ eccentric alternative (CMJ-Ecc-ALT) variables obtained during the CMJ AS and CMJ NAS. Twenty-two (men = 14, women = 8) NCAA Division 1 collegiate basketball players performed 3 CMJ AS and 3 CMJ NAS on a force plate, in a randomized order. To assess the test-retest reliability, participants returned 1 week later to perform 3 additional CMJ AS and 3 CMJ NAS. Intraclass correlation coefficient (ICC) and coefficient of variation (CV) were used to assess intersession and intrasession reliability for the various CMJ variables. A majority of CMJ-TYP and several CMJ-Conc-ALT and CMJ-Ecc-ALT variables exhibited adequate intersession and intrasession reliability (ICC > 0.700 and CV

Arm swinging is a typical feature of human walking: Continuous and rhythmic movement of the upper limbs is important to ensure postural stability and walking efficiency. However, several factors can interfere with arm swings, making walking more risky and unstable: These include aging, neurological diseases, hemiplegia, and other comorbidities that affect motor control and coordination. Objective assessment of arm swings during walking could play a role in preventing adverse consequences, allowing appropriate treatments and rehabilitation protocols to be activated for recovery and improvement. This paper presents a system for gait analysis based on Microsoft Azure Kinect DK sensor and its body-tracking algorithm: It allows noninvasive full-body tracking, thus enabling simultaneous analysis of different aspects of walking, including arm swing characteristics. Sixteen subjects with Parkinson’s disease and 13 healthy controls were recruited with the aim of evaluating differences in arm swing features and correlating them with traditional gait parameters. Preliminary results show significant differences between the two groups and a strong correlation between the parameters. The study thus highlights the ability of the proposed system to quantify arm swing features, thus offering a simple tool to provide a more comprehensive gait assessment.

OBJECTIVE: To explore to what extent neuronal coupling between upper and lower limb muscles during gait is preserved or affected in patients with Parkinson's Disease (PD).METHODS: Electromyography recordings were obtained from the bilateral deltoideus anterior and bilateral rectus femoris and biceps femoris muscles during overground gait in 20 healthy participants (median age 69 years) and 20 PD patients (median age 68.5 years). PD patients were able to walk independently (Hoehn and Yahr scale: Stage 2-3), had an equally distributed symptom laterality (6 left side, 7 both sides and 7 right side) and no cognitive problems or tremor dominant PD. Time-dependent directional intermuscular coherence analysis was employed to compare the neural coupling between upper and lower limb muscles between healthy participants and PD patients in three different directions: zero-lag (i.e. common driver), forward (i.e. shoulders driving the legs) and reverse component (i.e. legs driving the shoulders).RESULTS: Compared to healthy participants, PD patients exhibited (i) reduced intermuscular zero-lag coherence in the beta/gamma frequency band during end-of-stance and (ii) enhanced forward as well as reverse directed coherence in the alpha and beta/gamma frequency bands around toe-off.CONCLUSIONS: PD patients had a reduced common cortical drive to upper and lower limb muscles during gait, possibly contributing to disturbed interlimb coordination. Enhanced bidirectional coupling between upper and lower limb muscles on subcortical and transcortical levels in PD patients suggests a mechanism of compensation.SIGNIFICANCE: These findings provide support for the facilitating effect of arm swing instructions in PD gait.

Background The shoulder joint is immobilized in various positions after injury or reconstructive operative intervention. It is not clear how these immobilization positions in the shoulder joint affect gait. Research question Does the immobilized shoulder joint in different positions following shoulder surgery or injury affect gait? Methods A total of 38 healthy individuals with a mean age of 25.94 years and BMI of 25.66 kg/m2, underwent gait analysis in 4 different immobilized positions and normal gait. Gait parameters were evaluated using the GAITRite electronic walkway, and to determine symmetry, the bilateral spatiotemporal gait parameters were calculated using the Symmetry Index. Repeated-measures one way analysis of variance was used to compare the walking parameters in different positions. Results Velocity, step length and stride length were significantly decreased, and step width and single support time were increased in some immobilized positions (p Significance This cross-sectional simulation study may be important in demonstrating the clinical changes of gait in injuries, pathologies, and postoperative rehabilitation that require the immobilization of the shoulder joint. It could be recommended that arm swing is included in gait rehabilitation, gait and balance training can be provided to patients after shoulder immobilization.

Persons with upper limb loss (ULL) experience a high prevalence of falls, with the majority of falls occurring when walking. This issue may be related to altered arm dynamics, which play an important role in proactive mechanisms of locomotor stability. This study investigated effects of ULL and prosthesis use on proactive stability mechanisms, particularly if matching the mass and inertia of the impaired limb to the sound limb would enhance locomotor stability. Gait data were collected on adults with unilateral ULL during level walking while: (1) not wearing a prosthesis, (2) wearing their customary prosthesis, (3) wearing a mock prosthesis that matched the sound limb mass and inertia. Main and interaction effects of limb side and condition on trunk rotations, arm swing, step width, free vertical moment, and margin-of-stability were analyzed. Across conditions, arm swing, free vertical moment, and margin-of-stability were 2.27, 1.13, and 1.20 times greater, respectively, on the sound limb side than the impaired limb side. Persons with ULL display asymmetry in proactive mechanisms of locomotor stability with potentially greater medial-lateral stability on the sound limb side irrespective of prosthesis use, but heavier prostheses reduced the walking base of support. This bias may enhance fall risk on the impaired side if the prosthetic limb is used inappropriately to regain balance following a disturbance. Research is warranted to explore the consequences of this asymmetry on perturbation response.

Mosier, EM, Fry, AC, and Lane, MT. Kinetic contributions of the upper limbs during countermovement. J Strength Cond Res 33(8): 2066-2073, 2019-This study examined the kinetic contributions of the upper extremities during countermovement vertical jumps (CMVJs) while using arm swing (AS) or no arm swing (NAS) conditions. Fourteen healthy men ((Equation is included in full-text article.)± SD; age = 24.1 ± 3.9 years) volunteered for this investigation. Subjects performed in random order a total of 6 jumps consisting of 3 AS and 3 NAS CMVJs. A motion capture system was used to analyze the kinetic data. Paired samples t-tests were used to examine the subjects' mean differences in the AS and NAS CMVJ trials (p

Kershner, AL, Fry, AC, and Cabarkapa, D. Effect of internal vs. external focus of attention instructions on countermovement jump variables in NCAA Division I student-athletes. J Strength Cond Res XX(X): 000-000, 2019-The purpose of this study was compare the effect of internal and external focus of attention instructions on force-time characteristics of the countermovement jump (CMJ) in collegiate student-athletes. Forty-three resistance-trained men ((Equation is included in full-text article.)± SD; age = 20 ± 1.5 years) on an NCAA Division I baseball team volunteered to participate in this study. Each participant performed a total of 16 CMJs on a force platform while holding a wooden dowel on their shoulders to eliminate arm swing. Force and power parameters such as jump height (JH), peak velocity (PV), and mean concentric velocity (MCV) were calculated from force-time and position data. Paired-sample t-tests and Cohen's d effect sizes were used to examine differences between conditions. When subjects were instructed using an external focus, they demonstrated significantly (p < 0.05) greater JH, PV, and MCV compared with jumps performed with the internal focus (external JH = 48.0 ± 5.6 cm, internal JH = 46.4 ± 5.4 cm; external PV = 3.6 ± 0.3 m·s, internal PV = 3.5 ± 0.3 m·s; and external MCV = 2.31 ± 0.22 m·s, internal MCV = 2.25 ± 0.23 m·s). It is interesting to note that there was superior recall of the internal instructions during the manipulation checks that may suggest that the subjects consciously processed these instructions to a greater extent and reduced internal condition performance. These results indicate that instructions can alter the efficiency and performance of a skill. According to the literature and this study, if an optimum performance metric is desired, external focus of attention instructions should be used.

The aim of this study was to evaluate the effect of reduced effort on maximum countermovement jumps. Groups of unskilled and skilled jumpers performed countermovement jumps without an arm swing at 100% and 50% effort. The results revealed markedly reduced jump height and work performed at 50% effort, although the maximum force and power output remained virtually unchanged. The observed differences were consistent across individuals with different jumping skills. A possible cause of differences in changes across the tested variables was a reduced countermovement depth associated with the 50% effort jumps. It is known to cause an increase in maximum force and power outputs, but not in jump height. Therefore, the jump height and work performed may be more closely related to our sense of effort when jumping, rather than our maximum force and power output. From a practical perspective, the present findings reiterate the importance of maximizing effort for making valid assessments of muscle mechanical capacities, as tested by maximal vertical jumps and, possibly, other maximum performance tasks.

Background The Gait Assessment and Intervention Tool (G.A.I.T.) has been shown to be a comprehensive and objectively scored tool to assess gait in people with neurologic disease. However, there is only an English version of the scale, the language in which it was developed. Objective To carry out a cross-cultural adaptation of the Gait Assessment and Intervention Tool (G.A.I.T.) scale for its use in the Spanish-speaking population, and to study the content validity of the Spanish version. Design A cross-cultural adaptation and validation study of the G.A.I.T. Setting University Laboratory (Alcorcon, Madrid, Spain). Participants Not applicable. Methods or interventions Cross-cultural adaptation of a scale. Main outcome measurements The Spanish version of the G.A.I.T. was obtained using the double-translation and back-translation method, and a subsequent Expert Committee revision. The Expert Committee studied the content validity of the Spanish G.A.I.T. using the content validity index (CVI). Results The final version of the G.A.I.T. in Spanish was obtained after the cross-cultural process. The CVI was found to be excellent for the overall G.A.I.T. (0.94), and excellent for 87% of its 31 items (≥0.78). CVI was good for 10% of the items (arm swing and toes, CVI ≥0.72). Although 3% of items (shoulder and elbow position) showed CVI = 0.28, these items were retained for completeness. Conclusions The Spanish version of the G.A.I.T. was developed through a cross-cultural adaptation process from its original version in English, and according to an Expert Committee it has an excellent overall content validity.

Made available in DSpace on 2019-10-06T15:19:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-11-20 People with Parkinson's disease (PD) have decreased arm swing movements during walking, which can be related to PD motor signs and symptoms. In this context, the aim of this study was to determine the effects of an increased arm swing frequency or amplitude on the gait parameters in people with PD and healthy older adults. Seventeen individuals with PD and 19 older people were invited to walk on a 10 m pathway under three experimental conditions: (i) usual walking (no arm swing instructions); (ii) an increased arm swing amplitude; and (iii) an increased arm swing frequency. Both groups had an increased stride speed, vertical center of mass and arm swing accelerations and decreased double support time under the increased arm swing amplitude and frequency conditions. People with PD were able to modulate the gait parameters according to the experimental conditions, but at a smaller magnitude than the older individuals. These results indicate that bradykinesia and hypometria of gait can be positively overcome by increasing the amplitude and frequency of arm swing. Arm movements should be included in gait rehabilitation protocols for PD. São Paulo State University (UNESP) Institute of Biosciences Posture and Gait Studies Laboratory (LEPLO) University of Groningen University Medical Center Groningen Center for Human Movement Sciences São Paulo State University (UNESP) Institute of Biosciences Posture and Gait Studies Laboratory (LEPLO)

The arm elevation strategy assists in recovering stability during slips in healthy young and elderly individuals. However, in people with Parkinson’s Disease, one of the main motor symptoms affecting the upper limbs is reduced arm swing which intensifies throughout the course of the disease before becoming absent. This holds direct implications for these individuals when encountering slips as the arm elevation strategy is an integral component in the interlimb slip response to restore stability. Arm swing’s effect in recovering from slips in people with Parkinson’s Disease though remains unexamined. Twenty people with Parkinson’s Disease (63.78 ± 8.97 years) walked with restricted and unrestricted arm swing conditions on a dual-belt treadmill where slips were induced on the least and most affected sides. Data were collected on the CAREN Extended System (Motek Medical, Amsterdam, NL). The Margin of Stability, linear and angular trunk velocities, as well as step length, time, and width were calculated. Data were examined during the slipped step and recovery step. The restricted arm swing condition, compared to unrestricted, caused a faster step time during the slipped step. Compared to the most affected leg, the least affected had a wider step width during the slipped step. During the recovery step, the least affected leg had a larger anteroposterior Margin of Stability and longer step time than the most affected. No differences between our arm swing conditions suggests that the normal arm swing in our participants was not more effective at restoring stability after an induced slip compared to when their arm motion was restricted. This may be due to the arm elevation strategy being ineffective in counteracting the slip’s backward destabilization in these individuals. Differences between the legs revealed that our participants were asymmetrically impaired in their slip recovery response.

BACKGROUND: Human bipedal gait benefits from arm swing, as it drives and shapes lower limb muscle activity in healthy participants as well as patients suffering from neurological impairment. Also during gait initiation, arm swing instructions were found to facilitate leg muscle recruitment.RESEARCH QUESTION: The aim of the present study is to exploit the directional decomposition of coherence to examine to what extent forward and backward arm swing contribute to leg muscle recruitment during gait initiation.METHODS: Ambulant electromyography (EMG) from shoulder muscles (deltoideus anterior and posterior) and upper leg muscles (biceps femoris and rectus femoris) was analysed during gait initiation in nineteen healthy participants (median age of 67 ± 12 (IQR) years). To assess to what extent either deltoideus anterior or posterior muscles were able to drive upper leg muscle activity during distinct stages of the gait initiation process, time dependent intermuscular coherence was decomposed into directional components based on their time lag (i.e. forward, reverse and zero-lag).RESULTS: Coherence from the forward directed components, representing shoulder muscle signals leading leg muscle signals, revealed that deltoideus anterior (i.e. forward arm swing) and deltoideus posterior (i.e. backward arm swing) equally drive upper leg muscle activity during the gait initiation process.SIGNIFICANCE: The presently demonstrated time dependent directional intermuscular coherence analysis could be of use for future studies examining directional coupling between muscles or brain areas relative to certain gait (or other time) events. In the present study, this analysis provided neural underpinning that both forward and backward arm swing can provide neuronal support for leg muscle recruitment during gait initiation and can therefore both serve as an effective gait rehabilitation method in patients with gait initiation difficulties.

Background While walking, people swing their arms in a specific pattern. This specific arm swing pattern during walking has shown to have a beneficial effect on gait as it reduces walking energy cost and optimizes balance. In several patient populations the arm movements can be directly affected (e.g. in patients with acquired brain injury (ABI)), which in turn has a negative effect on their gait pattern, balance and energy cost of walking. Main text In December 2019, Kahn et al. published a paper in JNER concerning the quantification of upper limb associated reactions (ARs) during walking in people with ABI. ARs are defined as “an effort-dependent phenomenon causing an involuntary increase in upper limb muscle tone, with awkward and uncomfortable postures”. These upper limb ARs appear often in patients with ABI and can have an important effect on their gait. The authors calculated kinematic measures using three-dimensional gait analysis relating to range of motion, variability and mean position over the gait cycle for the different upper limb joints (shoulder, elbow, wrist) during self-selected steady-state walking. Based on differences they found between an ABI cohort and healthy control cohort, the authors concluded that they were able to quantify ARs during walking in this population. This calculation, however, is not specific for upper limb ARs. In fact, the authors calculated general measures of arm posture (e.g. mean position over the gait cycle) or arm movement (e.g. range of motion and variability) during gait. Previous research has already indicated that other factors than ARs can influence the posture or movement of the arm during gait in patients with brain injury, such as voluntary compensations for gait instability and contractures or spasticity of upper arm muscles. Yet, it is not possible to disentangle the different causes of the altered arm posture during steady-state walking based on the proposed measures. Conclusion The kinematic arm measures proposed by Kahn et al. (J Neuroeng Rehabil 16(1):160, 2019) are not a direct measure of ARs, but provide a quantification of overall deviation of arm posture or movement during gait. Depending on the specific study design these measures may provide insights in ARs.

Parkour speed-runs require performers (known as Traceurs) to negotiate obstacles with divergent properties such as angles, inclinations, sizes, surfaces, and textures in the quickest way possible. The quicker the run, the higher the performer is ranked. Performance in Parkour speed-runs may be regulated through Parkour Traceurs’ basic movement skill capacities given the physical requirements of the event. This study examined what functional movement skills correlate with Parkour speed-run performance. Nineteen male Parkour Traceurs undertook a physical testing battery inclusive of: agility T-test, maximal grip strength test, and maximal vertical and horizontal jumps across several jump modalities. For the speed-run, Parkour Traceurs navigated an indoor Parkour installation. Pearson’s correlation analyses (r) revealed that agility T-test performance showed a significant negative correlation with Parkour speed-run performance, whereas standing long jump and counter movement jump (with and without arm swing) were significantly positively correlated with Parkour speed-run performance. Concurrent with the intrinsically-linked building blocks in the Athletic Skills Model, the data from the present study suggest that performance in Parkour-speed-runs are underpinned by functional movement skills (jumping, running; arm swinging) and conditions of movement (agility), all of which encapsulate elements of basic motor properties (speed; strength). From a practical perspective, the agility T-test, standing long jump, and counter movement jump without and without arm swing can form a basic battery to evaluate the physical effects of Parkour speed-run interventions on functional movement skills.

Falls are common in daily life, often caused by trips and slips and, particularly in older adults, with serious consequences. Although arm movements play an important role in balance control, there is limited research into the role of arm movements during balance recovery after tripping in older adults. We investigated how older adults use their arms to recover from a trip and the difference in the effects of arm movements between fallers (n=5) and non-fallers (n=11).Sixteen older males and females (69.7±2.3 years) walked along a walkway and were occasionally tripped over suddenly appearing obstacles. We analysed the first trip using a biomechanical model based on full-body kinematics and force-plate data to calculate whole body orientation during the trip and recovery phase. With this model, we simulated the effects of arm movements at foot-obstacle impact and during trip recovery on body orientation.Apart from an increase in sagittal plane forward body rotation at touchdown in fallers, we found no significant differences between fallers and non-fallers in the effects of arm movements on trip recovery. Like earlier studies in young adults, we found that arm movements during the recovery phase had most favourable effects in the transverse plane: by delaying the transfer of angular momentum of the arms to the body, older adults rotated the tripped side more forward thereby allowing for a larger recovery step. Older adults that are prone to falling might improve their balance recovery after tripping by learning to prolong ongoing arm movements.

Parkinson's disease (PD) is a chronic condition that can be diagnosed and monitored by evaluating changes in the gait and arm movement parameters. In the gait movement, each cycle consists of two phases: stance and swing. Using gait analysis techniques, it is possible to get spatiotemporal variables derived from both phases.In this paper, we compared two techniques: wavelet and peak detection. Previously, the wavelet technique was assessed for the gait phases detection, and peak detection was evaluated for arm swing analysis. These methods were evaluated using a low-cost RGB-D camera as data input source. This comparison could provide a unified and integrated method to analyze gait and arm swing signals.Twenty-five PD patients and 25 age-matched, healthy subjects were included. Mann-Whitney U test was used to compare the continuous variables between groups. Hamming distances and Spearman rank correlation were used to evaluate the agreement between the signals and the spatiotemporal variables obtained by both methods.PD group showed significant reductions in speed (wavelet p = 0.001, peak detection p0.001) and significantly greater swing (wavelet p = 0.003, peak detection p =0.005) and stance times (wavelet p = 0.003, peak detection p =0.004). Hamming distances showed small differences between the signals obtained by both methods (16 to 18 signal points). A very strong correlation (Spearman rho0.8, p0.05) was found between the spatiotemporal variables obtained by each signal processing technique.Wavelet and peak detection techniques showed a high agreement in the signal obtained from gait data. The spatiotemporal variables obtained by both methods showed significant differences between the walking patterns of PD patients and healthy subjects. The peak detection technique can be used for integral motion analysis, providing the identification of the phases in the gait cycle, and arm swing parameters.Clinical Relevance- this establishes that peaks and wavelet techniques are comparable and may use it interchangeably to process signals from the gait of Parkinson's disease patients to support diagnosis and follow up made by a clinical expert.

In patients with Parkinson&rsquo, s disease (PD), arm swing changes are common, even in the early stages, and these changes are usually evaluated subjectively by an expert. In this article, hypothesize that arm swing changes can be detected using a low-cost, cloud-based, wearable, sensor system that incorporates triaxial accelerometers. The aim of this work is to develop a low-cost, assistive diagnostic tool for use in quantifying the arm swing kinematics of patients with PD. Ten patients with PD and 11 age-matched, healthy subjects are included in the study. Four feature extraction techniques were applied: (i) Asymmetry estimation based on root mean square (RMS) differences between arm movements, (ii) posterior&ndash, anterior phase and cycle regularity through autocorrelation, (iii) tremor energy, established using Fourier transform analysis, and (iv) signal complexity through the fractal dimension by wavelet analysis. The PD group showed significant (p &lt, 0.05) reductions in arm swing RMS values, higher arm swing asymmetry, higher anterior&ndash, posterior phase regularities, greater &ldquo, high energy frequency&rdquo, signals, and higher complexity in their XZ plane signals. Therefore, the novel, portable system provides a reliable means to support clinical practice in PD assessment.

Bordelon, NM, Jones, DH, Sweeney, KM, Davis, DJ, Critchley, ML, Rochelle, LE, George, AC, and Dai, B. Optimal load magnitude and placement for peak power production in a vertical jump: a segmental contribution analysis. J Strength Cond Res XX(X): 000-000, 2020-Weighted jumps are widely used in power training, however, there are discrepancies regarding which loading optimizes peak jump power. The purpose was to quantify the effects of load magnitudes and placements on the force, velocity, and power production in a countermovement vertical jump. Sixteen male and 15 female subjects performed vertical jumps in 7 conditions: no external load, 10 and 20% dumbbell loads, 10 and 20% vest loads, and 10 and 20% barbell loads with load percentages relative to body weight. Arm swing was encouraged for all, but the barbell load conditions. Kinematics were collected to quantify the whole-body (the person and external loads) forces, velocities, and power as well as segments' contributions to the whole-body forces and velocities. Repeated-measure analyses of variance were performed followed by paired comparisons. Jump heights were the greatest for the no external load and 10% dumbbell conditions. The 10 and 20% dumbbell conditions demonstrated the greatest peak whole-body power, while the 2 barbell conditions showed the lowest peak whole-body power. At the time of peak whole-body power, the 2 dumbbell and 2 vest conditions resulted in greater whole-body forces. Whole-body velocities were the greatest for the no external load and 10% dumbbell conditions. Holding the dumbbells in the hands magnified the effects of external loads in producing forces and velocities. The constraint of arm movements in the barbell conditions limited power production. These findings highlight the importance of load placement and arm swing in identifying the optimal configuration for power production in weighted jumps.

Humans often perform tasks that require them to carry loads, but the metabolic cost of carrying loads depends on where the loads are positioned on the body. We reasoned that carrying loads at the arms’ center of mass (COM) during walking might be cheap since arm swing is thought to be dominated by passive pendulum dynamics. In contrast, we expected that carrying loads at the leg's COM would be relatively expensive because muscular actuation is necessary to initiate and propagate leg swing. Therefore, we hypothesized that carrying loads at the arm's COM while swinging would be cheaper than carrying loads at the leg's COM. We further hypothesized that carrying loads at the arm's COM while swinging would be more expensive than carrying loads at the waist, where the mass does not swing relative to the body. We measured net metabolic power, arm and leg motion, and the free vertical moment while subjects (n=12) walked on a treadmill (1.25 m/s) with no-load, and with 8-kg added to the arms (swinging vs. not swinging), legs, or waist. We found that carrying loads on the arms or legs altered arm swinging amplitude; however, the free vertical moment remained similar across conditions. Most notably, the cost of carrying loads on the swinging arms was 9% less than carrying at the leg's COM (P

Jump performance provides meaningful information both for sporting and clinical needs. Current state-of-the-art in jump performance assessment is laboratory-bound, however, out-of-the-laboratory methods are desirable. Therefore, the purposes of the present investigation were 1) to explore whether utilising a novel analytical approach minimises the bias between inertial recording unit (IMU)-based and jump mat-based jump height estimates, and 2) to provide a thorough tutorial for a sport scientist (see appendix) to facilitate standardisation of jump height estimation. Forty one women, men and boys aged 6 to 77 years-of-age completed three maximal counter movement jumps without arm swing, which were concurrently registered with a jump mat, and an IMU worn in low lumbar region. Excellent agreement between the novel IMU-based jump height and jump mat jump height was observed (mean IMU 22.6 [8.3] cm, mean jump mat 22.7 [8.9], mean bias -0.1 cm [95% limits of agreement -4.5 cm to 4.4 cm; p = 0.826], intra-class correlation coefficient 0.97 [95% CI 0.94 to 0.98, p < 0.001]). In conclusion, inertial recordings conducted with lightweight IMUs worn on the hip provide a valid and feasible assessment of jump height among people with varying athletic ability. Inertial signals have the potential to afford (at least semi-) automated analysis pipeline with low labour cost thus being potentially feasible in applied settings such as in professional sports or in the clinics. peerReviewed

Previous studies have investigated how additional arm weights affect gait. Although light weights (0.45 kg) seemed to elicit performance improvements in Parkinsonian patients, it was not studied how light weights affect gait parameters in healthy individuals. It is important to understand normal responses in a healthy population so that clinical effects might be better understood. Therefore, the purpose of this study was to investigate the effects of arm weights on arm swing amplitude, gait performance, and muscle activity in healthy people. Twenty-two subjects walked overground at their preferred speed under different weight carriage conditions (C1: no weight; C2: unilateral arm weight; C3: bilateral arm weights; C4: waist weights). Gait speed increased in C2 (p = 0.018) and C4 (p = 0.013) when compared with C1(C1: 1.21 ± 0.08; C2: 1.25 ± 0.11; C3: 1.24 ± 0.11; C4: 1.25 ± 0.11 m/s) with an increase in cadence during C2 (p 0.001), C3 (p = 0.008), and C4 (p 0.001) (C1: 105.5 ± 5.2; C2: 108.5 ± 5.6; C3: 107.9 ± 5.6; C4: 108.5 ± 5.3 steps/min) and in tibialis anterior electromyographic activity on the unweighted side in C2 (p = 0.048) (C1: 21.05 ± 4.59; C2: 25.10 ± 6.10; C3: 23.93 ± 4.75; C4: 24.33 ± 6.32 μV). The results indicate that an additional sensory input with the application of the weights may result in an overcompensation with the whole body and facilitate faster walking speed when applied on one arm or around the waist. The locations of the weights and amount of the weights may elicit different responses. Various strategies of adding weights should be further investigated as a potential intervention to improve performance in individuals with various gait impairments. Although there is evidence for benefits of this intervention in Parkinsonian patients, further study is warranted in other patient populations, such as stroke patients, who might benefit from this intervention to improve gait performance.

This study aimed to identify the effects of rhythmic arm swing during robot-assisted walking training on balance, gait, motor function, and activities of daily living among patients with subacute stroke. Twenty patients with subacute stroke were recruited, and thereafter randomly allocated to either the experimental group that performed the robot-assisted walking training with rhythmic arm swing, or the control group that performed the training in arm fixation. In total, 30 training sessions were carried out. The outcome measures included the 10-m walk test, Berg balance scale, timed up-and-go test, fall index that was measured using the Tetrax system, motor function test of Fugl-Meyer assessment, and modified Barthel index. The patients of both groups showed significant improvement in all parameters after the intervention (P

Normal walking includes coordinated and controlled movement of the legs and arms. However, patients following stroke often present with inappropriate motor control which limits coordinated movement patterns of the affected limbs. This study aimed to compare the effects of rhythmic arm swing and arm fixation during treadmill walking in patients with poststroke hemiparesis. We used an alternating study design with multiple baselines across subjects. Three patients with chronic stroke participated in this study. During treadmill walking, rhythmic arm swing and arm fixation conditions were alternately applied. Outcome measures included the 10-meter walk test (10MWT) and energy expenditure index (EEI). In the intervention phase, all subjects showed significantly greater improvements in the 10MWT and EEI scores for rhythmic arm swing condition compared to those for arm fixation condition (p 0.05). 10MWT improvement rates: Subject 1-34.81% vs. 15.75%; Subject 2-40.00% vs. 17.95%; and Subject 3-38.08% vs. 21.85%; and EEI improvements: Subject 1-23.19% vs. 14.08%; Subject 2-26.15% vs. 20.43%; and Subject 3-22.99% vs. 14.49%. These findings suggest that rhythmic arm swing is clinically feasible as a more favorable option to enhance the effects of treadmill walking training. However, larger studies with a different study design are needed to be able to make any judgment about the usefulness of the treatment.

Background Direction changes while walking are more likely to cause a hip fracture than is falling while walking in a straight line. Trunk stability is an important contributor to safe and effective walking, and arm movements influence trunk movement while walking. However, the difference in the trunk stability during semicircular turns performed by elderly women with a light bag has not been examined. Objective To investigate the effects of carrying a bag on trunk stability during semicircular turns in elderly women. Methods We enrolled 15 community-dwelling elderly women capable of independent walking. Participants walked with and without a bag at a self-selected speed along a marked path, which included semicircular turns, while fitted with an accelerometer attached over the L3 spinous process. Results Gait velocity was faster during semicircular turning with a bag versus without a bag. The normalized medial-lateral center of mass acceleration was lower during semicircular turning with a bag versus without a bag. Conclusions We suggest that a light additional arm load and increased arm swing contributes to trunk stability and efficient walking during semicircular turning by elderly women.

The ability to jump high with precision is an important component of the ballet dancer's technique. The aim of this study was to evaluate the effect of a modified ballet class on strength and jumping ability in high level female dancers. Seventeen female ballet students were divided into two groups, experimental and control, and tested before and after an 8-week, 2 times/week intervention for peak torque of knee extensors and flexors at 60°and 180°, and jumping ability (squat jump, countermovement jump, countermovement with arm swing jump, sauté in first position, and sauté in first position with port de bras). Statistical analysis was performed using Analysis of Variance (Anova 2x2) with repeated measure of factor time (pre and post). T-test with Bonferroni adjustment was used to assess any differences between groups. The experimental group showed improvement in height (7.7%), takeoff velocity (4.0%), and power (5.1%) of the squat jump. In addition, increases were revealed in peak (60°, 11.9%; 180°, 7.8%) and relative peak torque (60°, 13.2%; 180°, 9.2%) of the right knee flexors. Moreover, enhancements of the knee flexor-extensor strength ratio in both angular velocities were found (60°, 10.4%; 180°, 9.7%). These outcomes suggest that the proposed program could help ballet dancers improve the height of their vertical jumps and leg strength.

Homo sapiens constitute the only currently obligate bipedal mammals and, as it stands, upright bipedal locomotion is a defining characteristic of humans. Indeed, while the evolution to bipedalism has allowed for the upper limbs to be liberated from ground contact during ambulation, their role in locomotion is far from obsolete. Rather, there is reason to believe that arm swing offers important mechanical and neurological advantages to bipedal locomotion. In this short review, we present some compelling findings on the neural connections between the arms and legs during human locomotion. We begin with a description of the importance of arm swing during walking from a mechanical perspective. Then, we examine evidence for the existence of interappendicular connections that converge along with peripheral afferents, descending inputs, and propriospinal projections, onto the neural circuits innervating the muscles of the arms and legs. The varied effects of interappendicular coupling on the neural control of locomotion are also examined in cases of neurological injury. We use the insight gained from these collected works as well as those from our own studies on locomotor training to discuss strategies to use interappendicular connections to rehabilitate walking in individuals experiencing loss of function after debilitating spinal cord injury.

Many field sports involve equipment that restricts one or both arms from moving while running. Arm swing during running has been examined from a biomechanical and physiologic perspective but not from an injury perspective. Moreover, only bilateral arm swing suppression has been studied with respect to running. The purpose of this study was to determine the influence of running with one arm restrained on lower extremity mechanics associated with running or sport-related injury. Fifteen healthy participants ran at a self-selected speed with typical arm swing, with one arm restrained and with both arms restrained. Lower extremity kinematics and spatiotemporal measures were analysed for all arm swing conditions. Running with one arm restrained resulted in increased frontal plane knee and hip angles, decreased foot strike angle, and decreased centre of mass vertical displacement compared to typical arm swing or bilateral arm swing restriction. Stride length was decreased and step frequency increased when running with one or both arms restrained. Unilateral arm swing restriction induces changes in lower extremity kinematics that are not similar to running with bilateral arm swing restriction or typical arm swing motion. Running with one arm restrained increases frontal plane mechanics associated with risk of knee injury.

WOS: 000496927900021, PubMed: 31683183, Background: Little is known about whether a simulated upper limb condition reflects a real (burn-injury) upper limb pathology in terms of gait/footprint parameters. Research question: The main aim of this study was to investigate the differences in these parameters between two conditions (real-simulation). Methods: The study included burn patients (n = 30) and a control group of 30 healthy subjects. Gait and footprint parameters were evaluated using the GAITRite electronic walkway. Kinesiophobia and pain were assessed with the Tampa Kinesiophobia Scale and Visual Analog Scale, respectively. Gait evaluation of the control group was performed randomly in two conditions:1. Normal arm swing (control group) 2. Elbow flexed at 90 degrees with a bandage (simulated group). Results: Step and stride length in the burn group were significantly shorter than in the other groups (p < 0.05). Stance phase was significantly higher while swing phase, velocity and cadence were lower in the burn group (p < 0.05). Peak time in the midfoot for both sides were significantly higher in the burn group (p < 0.05). Peak time in the hindfoot for the affected side was significantly lower while peak time in the hindfoot for the intact side was significantly higher in the burn group compared to the simulated group (p < 0.05). There were significant correlations between pain, kinesiophobia and velocity, and cadence in the burn group (p < 0.05). Significance: Compared to the other groups, patients with burn injury have different gait/footprint parameters due to increased pain and kinesiophobia. To determine the effects of upper limb injury and arm swing on gait parameters, a real pathology should be considered rather than a simulated pathology.

In order to provide an effective system for rehabilitation of walking, a new rotational orthosis for walking with arm swing, called ROWAS II, was developed. This study focused on development and implementation of admittance control of the ankle mechanism in the ROWAS II system for promoting active training. Firstly, the mechanical structure of the ankle mechanism is briefly introduced. Then the algorithms of the closed-loop position control and the admittance control for the ankle mechanism are described in detail. Four able-bodied participants were recruited to use the ankle mechanism running in passive and active modes. The experimental results showed that the ankle mechanism well tracked the target trajectory in passive mode. In active mode, the participants interacted with the ankle mechanism, and adjusted their ankle movement based on their active force. The ankle mechanism has the technical potential to meet the requirements of passive and active training in the ankle movement for patients in different post-stroke stages.

Fall induced injuries are a leading cause for occupational injuries with the majority originating from challenging same-level walking surfaces. Despite current perturbation and fall prevention paradigms, occupational fall prevalence remains stable. Typically, these paradigms do not account for arm swing which has been demonstrated to affect the center of mass′ movement during walking. This study examined the effect of different arm swing on postural control during symmetric and asymmetric walking. Fifteen healthy young adults (age = 23.4 ± 2.8) walked symmetrically and asymmetrically with three arm motions (normal, held, and active) on a split-belt treadmill CAREN Extended-System (Motek Medical, Amsterdam, NL). Mean, standard deviation and maximal values of trunk linear and angular velocity, and whole-body angular momentum were calculated in all three axes; additionally, step length, time and width mean and Coefficient of Variation, Margin of Stability and Harmonic Ratios were calculated. Compared to normal and held conditions, active arm increased trunk linear and angular velocity standard deviation, max velocity values, mean step length and time, as well as the Coefficient of Variation for step length, time, and width. Furthermore, whole-body angular momentum increased as a function of arm swing amplitude. Active arm swing further reduced Harmonic Ratios in the mediolateral and anteroposterior directions. Asymmetric walking increased average step time, and width as well as increased the Coefficient of Variation for step length and time but reduced left average step length and step width Coefficient of Variation. Further, asymmetric walking increased mediolateral Margin of Stability and reduced anteroposterior and mediolateral Harmonic Ratios. Finally, results demonstrated that actively increasing arm swing increases trunk linear and angular velocity variability in healthy young adults during symmetric and asymmetric treadmill walking. Findings may be due to active arm swing and asymmetric walking causing a disproportional contribution to trunk and center of mass movement causing participants to modify their base of support to maintain stability.

Stereotypically, walking and running gaits in humans exhibit different arm swing behavior: during walking, the arm is kept mostly straight, while during running, the arm is bent at the elbow. The mechanism for this behavioral difference has not been explored before. We hypothesized that a mechanical tradeoff exists between the shoulder joint and the elbow joint. Bending the elbow reduces the radius of gyration of the arm and reduces shoulder muscle torque, but at the price of increasing elbow torque. We predicted that the mechanical tradeoff would result in energetics that favored straight arms during walking and bent arms during running. The hypothesis was tested experimentally by having eight subjects walk and run with both straight arms and bent arms while recording arm swing mechanics, and oxygen consumption in a subset of six subjects. The mechanical tradeoff hypothesis was confirmed, with bent arms reducing normalized shoulder muscle torque in both gaits (walking: −33%, running: −32%) and increasing normalized elbow muscle torque in both gaits (walking: +110%, running: +30%). Bent arms increased oxygen consumption by 11% when walking, supporting our prediction that energetics favor straight arms during walking. However, oxygen consumption was equivalent for the straight and bent arm running conditions, and did not support our running prediction. We conclude that straight arms are stereotyped in walking as a result of optimal energetics, while the mechanism leading to bent arms during running remains unknown.

Ramirez-Campillo, R, Moran, J, Drury, B, Williams, M, Keogh, JW, Chaabene, H, and Granacher, U. Effects of equal volume but different plyometric jump training intensities on components of physical fitness in physically active young males. J Strength Cond Res 35(7): 1916-1923, 2021-An 8-week single-blind randomized controlled trial was conducted to compare the effects of separate programs of equal volume, but different intensity, plyometric jump training (PJT), on physical fitness in healthy adults. Thirty-eight physically active males (mean age: 21.8 ± 2.5 years) participated. Subjects were randomly assigned to one of 3 PJT groups or a control (CON, n = 9) according to their jump performance. Plyometric jump training was conducted at maximal (PJT-100, n = 10), high (PJT-80, n = 9), or moderate (PJT-65, n = 10) intensity within each group. Baseline and follow-up tests were performed for the assessment of countermovement jump (CMJ) height, CMJ height with arm swing (CMJA), and drop jump height from a 20-cm drop box (DJ20), linear speed (30 m), and change-of-direction speed (CODS) (the Illinois CODS test). Results revealed significant group × time interactions for CMJ, CMJA, DJ20, 30-m sprint, and CODS (all p < 0.001; d = 0.39-0.76). Post hoc analyses showed significant improvements in all 5 fitness measures for PJT-100 (all p < 0.01, Δ3.7-13.5%, d = 0.26-1.4). For PJT-80, 3 of 5 fitness tests demonstrated significant change (CMJ: p < 0.001, Δ5.9%, d = 0.33; CMJA: p < 0.001, Δ7.0%, d = 0.43; CODS: p < 0.001, Δ3.9%, d = 0.9), and for PJT-65, only 1 test was significant (CMJ: p < 0.05, Δ2.8%, d = 0.15). No significant changes were observed in CON. Except for similar gains in DJ20 and 30-m sprint in PJT-100 and PJT-80, gains in physical fitness were, in general, greater (p < 0.05) after PJT-100 vs. PJT-80 vs. PJT-65 vs. CON. Therefore, maximal PJT intensity may induce larger physical fitness gains, although high and moderate intensities may also be useful, but to a lesser extent.

The coordination of axial thorax and pelvis rotations during gait has been shown to be affected by several pathologies. This has been interpreted as an indication of increased apparent axial trunk stiffness, but arm swing may also affect these rotations. The objectives of this study were to assess the effect of trunk stiffness and arm swing on the relative timing (‘coordination’) between thorax and pelvis rotations, and to assess if apparent trunk stiffness can be inferred from thorax-pelvis kinematics. A forward dynamic model was constructed to estimate apparent trunk stiffness from observed thorax and pelvis rotations and arm swing moment around the longitudinal axis of the trunk of 30 subjects. The effect of independent manipulations of trunk stiffness and arm swing moment on thorax-pelvis coordination and gain of axial thorax-pelvis rotations were assessed using the same forward dynamic model. A linear regression model was constructed to evaluate whether forward dynamic model-based estimates of axial trunk stiffness could be inferred directly from thorax-pelvis rotations. The forward dynamic model revealed that axial trunk stiffness and arm swing moment have opposite effects on axial thorax-pelvis coordination. Apparent axial trunk stiffness could not be predicted from observed thorax-pelvis rotations.

Humans naturally select conditions to minimize their net cost of transport (COT) during walking. One way to do this is by exploiting the mechanical benefit of arm swing which reduces whole-body rotation about the vertical axis and thus, minimizes the free vertical moment (FVM) that the foot applies to the ground. Humans appear to exploit these benefits of arm swing at speeds that are considered optimal, but we sought to determine if these benefits are conserved across slow to fast walking speeds. If true, arm swing may be a key feature that helps to minimize the net COT regardless of one's walking speed. We hypothesized that at all speeds, walking with arm swing would be less costly compared to walking without arm swing. As a secondary aim, we also explored if reductions in the peak FVM could explain the metabolic benefits of arm swing. Twenty-one young, healthy subjects walked with and without arm swing at speeds ranging from 0.50 to 2.00 m/s while we recorded metabolic, kinematic and kinetic data. At slow speeds (≤1.00 m/s), net COT was similar when walking with or without arm swing (p 0.05). However, at intermediate and fast speeds (≥1.00 m/s), arm swing reduced the net COT by ~7-13% (all p's 0.05). Additionally, peak FVM magnitudes decreased with arm swing, suggesting that it may partially explain the metabolic benefit of arm swing. Overall, we find that arm swing provides a net metabolic benefit during walking, but this benefit is constrained to intermediate and fast walking speeds.

Continuous inter-limb coordination and the ability to offset perturbations to a movement pattern (i.e., stability) are important factors in efficient motor performance. Patients with movement disorders often show deficits in coordination and stability, although little is known about these features in children with cerebral palsy. The purpose of this study was to identify the continuous inter-limb coordination and stability deficits in children with cerebral palsy and determine if improvement occurs with upper extremity intervention.Children with cerebral palsy participated in bimanual or unimanual intensive therapy. Continuous inter-limb coordination between the arms and between the more-affected arm and leg was evaluated using relative phase analysis during four gross motor tasks, including in-place marching and standing with asymmetric and symmetric arm swing. A control group of children with cerebral palsy and a group of typically developing children were also evaluated.Children with cerebral palsy displayed coordination deficits compared to typically developing children (p0.01), yet both groups presented similarly poor levels of stability (p=0.39). Compared to standing, adding legs to the task negatively impacted the coordination (p0.01) and stability (p0.01) of all children. Both groups improved coordination between the arms post-intervention (p0.05 for all cases), however neither group improved stability (p0.05 for all cases).Relative phase analysis successfully provided a sensitive measurement of coordination and stability in pathologic and non-pathologic populations. Findings indicate that all children have difficulty producing consistent movement patterns and suggest that both bimanual and unimanual interventions can improve continuous coordination in children with cerebral palsy.

The aim of this study was to examine the dose response effect of strength and conditioning programmes, involving horizontally oriented plyometric exercises, on relevant soccer performance variables. Sixteen soccer players were randomly allocated to two 6-week plyometric training groups (G1 and G2) differing by imposed (twice a week) training volume. Post-training G1 (4.13%; d = 0.43) and G2 (2.45%; d = 0.53) moderately improved their horizontal countermovement jump performance. Significant between-group differences (p 0.01) in the vertical countermovement jump for force production time (T2) were detected post-training. No significant and practical (p 0.05, d = trivial or small) post-training improvements in sprint, change of direction ability (CODA) and horizontal arm swing countermovement jump were reported in either group. Horizontal plyometric training was effective in promoting improvement in injury prevention variables. Doubling the volume of a horizontal plyometric training protocol was shown to have no additional effect over functional aspects of soccer players' performance.

Casting of the arm may interfere with normal walking patterns because of additional load of the cast or prevention of arm swing. This study aimed to determine the effect of applying various casts on temporospatial walking parameters, including gait velocity and cadence, step length, and single limb support. A computerized gait system was used to assess these variables for 23 healthy individuals in four walking modes: normal walking, with a cast above the elbow and a sling, and with a cast below the elbow, with and without a sling. Thirteen participants had their dominant hand casted and 10 had their nondominant hand casted. On average, casted participants took significantly smaller steps with the leg on the casted side and spent less time supported on the casted side. The least changes were noted with the arm in a cast below the elbow and no sling, and the greatest changes were noted with the arm in a cast above the elbow and in a sling. This difference was heightened when the dominant hand was casted and lessened when the nondominant hand was casted. No differences were found in walking velocity or cadence between the walking modes. Casting of the upper limb has significant effects on gait, which should be taken into consideration, especially in individuals with previous gait abnormalities.

The study investigated the effects of arm swing during leg push-off in V2-alternate/G4 skating on neuromuscular activation and force production by the leg muscles. Nine skilled cross-country skiers performed V2-alternate skating without poles at moderate, high, and maximal speeds, both with free (SWING) and restricted arm swing (NOSWING). Maximal speed was 5% greater in SWING (P

The present study investigated the contribution of the Hof (2007) mechanism 1 (M1-moving the center of pressure (COP) with respect to the vertical projection of the center of mass (COMTotal)); and mechanism 2 (M2-rotating the trunk and upper limbs around the COMTotal) to postural control and the stability of COP-COMTotal cophase as a function of lateral arm-swing frequency. Young adults were instructed to stand still on a force platform while alternating their arm swinging from above the head to the side of their thigh to create perturbations to postural control. Scaling the frequency of arm-swing (random step changes of 0.2 Hz within a bandwidth of 0.2 to 1.6 Hz) increased the SD of COP but decreased the SD of COMTotal. Increments in arm-swing frequency induced a progressive increase in M1 and decrease in M2 in terms of their relative contribution to postural stability. The cophase between COP and COMTotal became more tightly in-phase over increments of arm-swing frequency. These findings show an adaptive compensatory role of M1 and M2 within the stability of COP-COMTotal coupling in the regulation of human balance control.

Weighting the arms during locomotion results in decreased swing motion and increased shoulder muscle activity. To determine the functional relevance of this activity, participants walked on a treadmill with the arms unweighted, or weighted unilaterally or bilaterally. Similar to past work, the weighted arms decreased in swing amplitude and increased their shoulder muscle activity. A close examination of shoulder muscle activities in specific regions of the arm swing cycle suggested these muscles primarily acted eccentrically for all weighting conditions. These findings suggest that the increased shoulder muscle activities when weighting the arms act to dampen the arms when the inertial characteristics of the arms are altered, as opposed to assisting in driving swing of the heavier arms.

The clinical characteristics of adult spinal deformity (ASD) include worsening of deformity during gait, which leads to unstable posture and propensity to fall. The purpose of this study was to classify arm swing and to analyse its clinical implications. Clinical and radiographic evaluations were performed with 168 community-dwelling female volunteers recruited from a population register in Hokkaido, Japan, with a mean age of 67.3 ± 4.7 years, and arm swing was classified into four groups according to maximum forward and backward arm swing distance: (1) predominantly forward swing with forward swing always larger than backward swing (FS, n = 138), (2) equal or equivocal swing (ES, n = 8), (3) predominantly backward swing with backward swing always larger than forward swing (BS, n = 20), and (4) thigh-hand type without arm swing with their hands placed on thighs (TH, n = 2). BS and FS showed significant differences in radiographic lumbar lordosis (BS 19.4 ± 18.1° vs. FS 40.6 ± 14.5°, P de novo/idiopathic scoliosis, degenerative/osteoporotic kyphosis, and other neuromuscular deformities, has been increasing, and further study should clarify the importance of dynamic evaluation of ASD among elderly patients.

Magrini, MA, Colquhoun, RJ, Sellers, JH, Conchola, EC, Hester, GM, Thiele, RM, Pope, ZK, and Smith, DB. Can squat jump performance differentiate starters vs. nonstarters in division I female soccer players? J Strength Cond Res 32(8): 2348-2355, 2018-Although soccer is predominately an endurance sport, high velocity movements may be an important indicator of athletic success. The purpose of this investigation was to establish whether squat jumps (SJs) can differentiate starters from nonstarters with a female collegiate division I soccer team. Eighteen female division I soccer athletes were separated into 2 groups: 9 starters (age: 19.5 ± 1.0; mass = 64.8 ± 11.5 kg; height = 167.5 ± 7.7 cm; games started = 18.2 ± 4.7; and minutes played = 1633.8 ± 478.2 minutes) and 9 nonstarters (age: 19.4 ± 1.4 years; mass = 63.3 ± 4.2 kg; height = 164.7 ± 6.8 cm; games started 0.7 ± 1.3; and minutes played 158.2 ± 269.3 minutes). Each athlete performed 3 maximal SJs at a starting knee angle of 110° without arm swing. Each participant's SJ height, mean power (MP), peak power (PP), mean velocity (MV), and peak velocity (PV) were measured during each attempt by a linear position transducer. No statistically significant differences (p ≥ 0.05) in MP and PP between the starters and nonstarters were observed. However, starters performed significantly better than nonstarters in SJ height (p = 0.002), MV (p = 0.025), and PV (p = 0.015). In addition, SJ height was strongly correlated with MV (r = 0.628) and PV (r = 0.647). These findings suggest that SJ height, MV, and PV may be important variables for discriminating differences between starters and nonstarters in division I female soccer athletes and a strong indicator of explosive performance.

BACKGROUND: Human gait benefits from arm swing, which requires four-limb co-ordination. The Supplementary Motor Area (SMA) is involved in multi-limb coordination. With its location anterior to the leg motor cortex and the pattern of its connections, this suggests a distinct role in gait control.RESEARCH QUESTION: Is the SMA functionally implicated in gait-related arm swing?METHODS: Ambulant electroencephalography (EEG) was employed during walking with and without arm swing in twenty healthy subjects (mean age: 64.9yrs, SD 7.2). Power changes across the EEG frequency spectrum were assessed by Event Related Spectral Perturbation (ERSP) analysis over both the putative SMA at electrode position Fz and additional sensorimotor regions.RESULTS: During walking with arm swing, midline electrodes Fz and Cz showed a step-related pattern of Event Related Desynchronization (ERD) followed by Event Related Synchronization (ERS). Walking without arm swing was associated with significant ERD-ERS power reduction in the high-beta/low-gamma band over Fz and a power increase over Cz. Electrodes C3 and C4 revealed a pattern of ERD during contralateral- and ERS during ipsilateral leg swing. This ERD power decreased in gait without arm swing (low-frequency band). The ERSP pattern during walking with arm swing was similar at CP1 and CP2: ERD was seen during double support and the initial swing phase of the right leg, while a strong ERS emerged during the second half of the left leg's swing. Walking without arm swing showed a significant power reduction of this ERD-ERS pattern over CP2, while over CP1, ERS during left leg's swing turned into ERD.CONCLUSION: The relation between arm swing in walking and a step-related ERD-ERS pattern in the high-beta/low-gamma band over the putative SMA, points at an SMA contribution to integrated cyclic anti-phase movements of upper- and lower limbs. This supports a cortical underpinning of arm swing support in gait control.

Background Tennis serve is the most important shot in tennis. Lower limbs generate about 50% of the total force developed during the serve, but limited information is available about their role. Therefore, the aim of the present study was to investigate the role of lower limbs during first and second serve and its relationship between jump height and ball speed during tennis serve. Methods Eight professional tennis players (age: 20±3 years; height 181±3 cm; height with racket: 283±5 cm; playing experience 13±3 years) were tested with counter movement jump (CMJ) and CMJ with free arm swing (CMJF). Moreover, jump height and serve speed during first and second serve were measured. Results No significant differences between the first and the second serve jump height were observed. Significant difference between the best CMJ and jump height during the first (37.29±4.94 vs. 12.42±3.28, P=0.0006; effect size [ES]: >2.0) and the second (37.29±4.94 vs. 13.04±2.46, P=0.0002; ES: >2.0) serve was noted. Significant difference between the best CMJF performance and the best jump height during the first (44.46±6.22 vs. 12.42±3.28, P=0.0006; ES: >2.0) and the second (44.46±5.82 vs. 13.04±2.46, P=0.0002; ES: >2.0) serves were detected. Slightly significant Spearman positive correlations between jump height and first (P=0.049; r=0.71) and second (P=0.047; r=0.71) serve speed was computed. Conclusions Reaching higher impact point during tennis serve could allow to serve faster. On the other hand, because tennis serve is a complex coordinative movement of the entire kinetic chain, coaches should focus more coordinative skills of their athletes.

Treadmill experiments suggest that left-dominant arm swing is common in healthy walking adults and is modulated by cognitive dual-tasking. Little is known about arm swing asymmetry in overground walking. We report directional (dASI) and non-directional arm swing symmetry indices (ndASI) from 334 adults (mean age 68.6 ± 5.9 y) walking overground at comfortable (NW) and fast (FW) speeds and while completing a serial subtraction task (DT). dASI and ndASI were calculated from sagittal shoulder range of motion data generated by inertial measurement units affixed to the wrist. Most (91%) participants were right-handed. Group mean arm swing amplitude was significantly larger on the left in all walking conditions. During NW, ndASI was 39.5 ± 21.8, with a dASI of 21.9 ± 39.5. Distribution of dASI was bimodal with an approximately 2:1 ratio of left:right-dominant arm swing. There were no differences in ndASI between conditions but dASI was smaller during DT compared to FW (15.2 vs 24.6; p = 0.009). Handedness was unrelated to ndASI, dASI or the change in ASI metrics under DT. Left-dominant arm swing is the norm in healthy human walking irrespective of walking condition or handedness. As disease markers, ndASI and dASI may have different and complementary roles.