Reactive responses of the arms increase the Margins of Stability and decrease center of mass dynamics during a slip perturbation

Although reactive arm motions are important in recovering from a slip event, the biomechanical influences of upper extremity motions during slipping are not clear. The purpose of the current study was to determine whether reactive arm motions during slip recovery leads to increased margins of stability (MoS), and decreased center of mass (CoM) velocity and excursion. Thirty-two participants were randomized into 2 conditions: arms free and arms constrained. Participants traversed a 10-meter walkway and were exposed to an unexpected slip while wearing a protective harness. Anterior-posterior and medial-lateral MoS, as well as the CoM excursion and velocity during the slip perturbation was quantified using a three-dimensional motion capture system. In the frontal plane, individuals with their arms unconstrained demonstrated greater MoS (0.06 ± 0.03 vs -0.01 ± 0.02 m, p < 0.01), decreased CoM excursion (0.05 ± 0.02 vs 0.08 ± 0.01 m, p = 0.015), and a reduced CoM velocity (0.07 ± 0.03 vs. 0.14 ± 0.02 m/s, p < 0.01) compared to individuals with their arms constrained. In the sagittal plane, individuals with their arms unconstrained demonstrated, decreased CoM excursion (0.83 ± 0.13 vs 1.14 ± 0.20 m, p < 0.01) reduced CoM velocity (1.71 ± 0.08 vs. 1.79 ± 0.07 m/s, p = 0.02), but no differences in margins of stability (0.89 ± 0.13 vs 0.94 ± 0.10 m, p = 0.32). Our findings demonstrate that arm motions during a slip perturbation act to restore balance by minimizing displacement and velocity of the body CoM during a slip event in the frontal plane.

Hemispheric Differences in Self-evaluation Errors of Upper Extremity Movement in Patients with Chronic Stroke

OBJECTIVE

There is growing evidence that the side of brain lesions results in distinct upper extremity deficits in motor control, movement behavior, and emotional and cognitive function poststroke. We investigated self-evaluation errors, which are the differences in scores between patient self-evaluation and clinician evaluations, and compared patients with left hemisphere damage (LHD) and right hemisphere damage (RHD) poststroke.

METHOD

Twenty-eight patients with chronic stroke (LHD = 16) performed the actual amount of the test twice with a one-week interval. We videotaped the participants' movements, and participants with stroke and evaluators graded the quality of movement scores by watching video recordings.

RESULTS

Self-evaluation errors were significantly lower in patients with LHD than in those with RHD (t = 2.350, p = .019). Interestingly, this error did not change after the clinician provided the correct score as feedback. Chi-squared analysis revealed that more patients with LHD underestimated their movements (χ² = 9.049, p = .002), while more patients with RHD overestimated (χ² = 7.429, p = .006) in the send evaluation. Furthermore, there were no correlations between self-evaluation error and age, cognitive function, physical impairment, ability to control emotions, or onset months poststroke.

CONCLUSIONS

Patients with stroke and therapists evaluated the same movements differently, and this can be dependent on hemispheric damage. Therapists might need to encourage patients with LHD who underestimate their movement to ensure continuous use of their more-affected arm. Patients with RHD who overestimate their movement might need treatment to overcome impaired self-awareness, such as video recordings, to protect from unexpected dangerous situations.

Using a simple rope-pulley system that mechanically couples the arms, legs, and treadmill reduces the metabolic cost of walking

BACKGROUND

Emphasizing the active use of the arms and coordinating them with the stepping motion of the legs may promote walking recovery in patients with impaired lower limb function. Yet, most approaches use seated devices to allow coupled arm and leg movements. To provide an option during treadmill walking, we designed a rope-pulley system that physically links the arms and legs. This arm-leg pulley system was grounded to the floor and made of commercially available slotted square tubing, solid strut channels, and low-friction pulleys that allowed us to use a rope to connect the subject's wrist to the ipsilateral foot. This set-up was based on our idea that during walking the arm could generate an assistive force during arm swing retraction and, therefore, aid in leg swing.

METHODS

To test this idea, we compared the mechanical, muscular, and metabolic effects between normal walking and walking with the arm-leg pulley system. We measured rope and ground reaction forces, electromyographic signals of key arm and leg muscles, and rates of metabolic energy consumption while healthy, young subjects walked at 1.25 m/s on a dual-belt instrumented treadmill (n = 8).

RESULTS

With our arm-leg pulley system, we found that an assistive force could be generated, reaching peak values of 7% body weight on average. Contrary to our expectation, the force mainly coincided with the propulsive phase of walking and not leg swing. Our findings suggest that subjects actively used their arms to harness the energy from the moving treadmill belt, which helped to propel the whole body via the arm-leg rope linkage. This effectively decreased the muscular and mechanical demands placed on the legs, reducing the propulsive impulse by 43% (p < 0.001), which led to a 17% net reduction in the metabolic power required for walking (p = 0.001).

CONCLUSIONS

These findings provide the biomechanical and energetic basis for how we might reimagine the use of the arms in gait rehabilitation, opening the opportunity to explore if such a method could help patients regain their walking ability.

TRIAL REGISTRATION

 Study registered on 09/29/2018 in ClinicalTrials.gov (ID-NCT03689647).

Variations of handheld loads increase the range of motion of the lumbar spine without compromising local dynamic stability during walking

BACKGROUND

Walking is often considered a beneficial management strategy for certain populations of low back pain patients. However, little is known about how simple challenges that people often encounter, such as carrying loads in the hands, affect the low back during walking.

RESEARCH QUESTION

How do variations in hand loading affect arm swing, lumbar spine range of motion (ROM), and lumbar spine local dynamic stability (LDS) during walking?

METHODS

Sixteen young healthy participants (8 female) performed nine treadmill walking trials, each at 1.25 m/s for 3 consecutive minutes. Conditions manipulated the magnitude of hand loads (unloaded, low, high) and location of hand loads (directly in hands, in bags). Kinematic markers were used to measure sagittal plane arm swing, 3D lumbar spine ROM, and lumbar spine LDS during each trial.

RESULTS

Arm swing was significantly (p < 0.001) reduced as load increased directly in the hands; however, when held in bags load magnitude had no effect. Further, arm swing was significantly (p < 0.0001) lower when loads were held in bags. Lumbar flexion/extension ROM was greatest with the low load compared to both unloaded (p = 0.012) and high load (p = 0.0717) conditions, and was also greater (p < 0.0001) with loads held directly in the hands compared to loads in bags. Despite these changes in lumbar spine ROM, lumbar spine LDS was not significantly affected by any of the variations in hand loading.

SIGNIFICANCE

The greater lumbar spine cyclic motion, elicited by low hand loads held directly in the hands during walking, may be beneficial to the health of the low back. No changes in lumbar LDS were found, thereby suggesting that the small, likely beneficial, increases in lumbar spine ROM are well controlled by the motor control system and do not create an increased risk of injury.

Recovery of upper-body muscle power after short intensive exercise: comparing boys and men

PURPOSE

Boys' lower-body muscle power generation (PO) recovers faster than men's following intensive exercise. The purpose of this study was to examine whether boys differ from adult men in recovering from upper-body muscle power generation following intensive exercise.

METHODS

Fifteen prepubertal boys (M ± SD age 10.6 ± 1.0 years) and 13 men (31.1 ± 5.0 years) performed two upper-body Wingate Anaerobic Tests (WAnT), separated by either 2-min or 10-min recovery intervals. WAnT parameters, pre-and post-WAnT heart rates (HR), and blood lactate ([La]) were measured during recovery from the WAnTs.

RESULTS

Boys' mean power (MP) of the repeated WAnT (WAnT₂) following 2- and 10-min recoveries was 97.3 ± 7.2% and 99.4 ± 3.9%, respectively, compared to MP of the first test (WAnT₁) (p > 0.05 for both tests). In contrast, in men's MP of the WAnT₂ following the 2-min recovery, was significantly lower than that of the WAnT₁ (84.4 ± 6.7%, p = 0.0001). While boys' and men's HR recovery after 2 min differed significantly (p = 0.046), no between-group differences were found following the 10-min recovery. Peak [La] in boys was 37-44% lower than that in men (p = 0.002).

CONCLUSIONS

The faster recovery of PO in boys after supra-maximal upper-body exercise is partially explained by the lower power generated by boys, attributed in part to a lower anaerobic capacity and to the greater relative contribution of aerobic processes to performance and recovery from anaerobic-type tasks. Further research is needed to determine the physiologic, neurologic and biochemical basis of the rapid muscle power recovery in children.

Upper limb movement analysis during gait in multiple sclerosis patients

PURPOSE

Gait disorders in multiple sclerosis (MS) are well studied; however, no previous study has described upper limb movements during gait. However, upper limb movements have an important role during locomotion and can be altered in MS patients due to direct MS lesions or mechanisms of compensation. The aim of this study was to describe the arm movements during gait in a population of MS patients with low disability compared with a healthy control group.

METHODS

In this observational study we analyzed the arm movements during gait in 52 outpatients (mean age: 39.7±9.6years, female: 40%) with relapsing-remitting MS with low disability (mean EDSS: 2±1) and 25 healthy age-matched controls using a 3-dimension gait analysis.

RESULTS

MS patients walked slower, with increased mean elbow flexion and decreased amplitude of elbow flexion (ROM) compared to the control group, whereas shoulder and hand movements were similar to controls. These differences were not explained by age or disability.

CONCLUSION

Upper limb alterations in movement during gait in MS patients with low disability can be characterized by an increase in mean elbow flexion and a decrease in amplitude (ROM) for elbow flexion/extension. This upper limb movement pattern should be considered as a new component of gait disorders in MS and may reflect subtle motor deficits or the use of compensatory mechanisms.

The efficacy of cryolipolysis treatment on arms and inner thighs

Cryolipolysis has emerged as a new non-invasive body contouring method using controlled cooling to selectively destroy fat cells. Previous studies demonstrated the safety and efficacy of cryolipolysis for the reduction of localized subcutaneous fat on abdomen and flanks. Recently, the new flat cup vacuum applicator has been developed to treat localized subcutaneous fat on arms and inner thighs. The objective of this study was to determine the efficacy of non-invasive cryolipolysis for body contouring with a flat cup vacuum applicator on arms and inner thighs. Twenty females with excess localized subcutaneous fat on arms or inner thighs received a single cryolipolysis treatment. Forty treatment areas have been treated including 10 arms and 30 inner thighs. Subjects were evaluated using standardized photographs and measurements of body weight and circumference of arms or inner thighs at baseline, 3-month, and 6-month follow-up visits. Physicians' evaluation and patient's satisfaction of clinical improvement were also measured. Of all 20 subjects, 17 (10 arms and 24 inner thighs) completed the treatment protocol and attended all follow-up visits. Three subjects were withdrawn from the study, 1 subject could not complete the treatment session due to pain and numbness during treatment, 1 subject became pregnant after treatment, and the other subject could not attend all required follow-up visits. There was significant circumference reduction of 0.41 and 0.72 cm at 3-month and 6-month follow-up visits (p = 0.017), respectively. Most of the patients were rated to have 1-25% improvement at 6 months after treatment and were satisfied with the treatment outcome. The new cryolipolysis flat cup vacuum applicator provided beneficial effects for circumferential reduction of arms and inner thighs.

A descriptive analysis of the upper limb patterns during gait in individuals with cerebral palsy

Patients with cerebral palsy (CP) are characterized by a large diversity of gait deviations; thus, lower limb movements during gait have been well-analyzed in the literature. However, the question of upper limb movements and, more particularly, arm movements during gait has received less attention for CP patients as a function of the disease type (Hemiplegic, HE or Diplegic, DI). Thus, the aim of this study was to investigate upper limb movements for a large group of CP patients; we used a retrospective search, including upper limb kinematic parameters and 92 CP patients (42 females and 50 males, mean±standard deviation (SD); age: 15.2±6.7 years). The diagnoses consisted of 48 HE and 44 DI. A control group of 15 subjects (7 females and 8 males, age: 18.4±8.4 years) was included in the study to provide normal gait data. For the DI patients and CG, 88 arms and 30 arms were analyzed, respectively. For the HE patients, 48 affected arms and 48 non-affected arms were analyzed. The kinematic parameters selected and analyzed were shoulder elevation angles; elbow flexion angles; thorax tilt and obliquity angles; hand vertical and anterior-posterior movements; and arm angles. Several gait parameters were also analyzed, such as the gait profile score (GPS) and normalized speed. Statistical analyses were performed to compare CG with the affected and non-affected upper limbs of HE patients and with the two upper limbs of DI patients. The results show that HE and DI patients adopt abnormal upper limb movements. However, DI patients have greater shoulder, elbow, thorax and arm angle movements compared with HE patients. However, HE patients adopt different movements between their affected and non-affected arms. Thus, the patients used their upper limbs to optimize their gait more where gait deviations were more important. These observations confirm that the upper limbs must be integrated into rehabilitation programs to improve inter-limb coordination.

The how and why of arm swing during human walking

Humans walk bipedally, and thus, it is unclear why they swing their arms. In this paper, we will review the mechanisms and functions of arm swinging in human gait. First, we discuss the potential advantages of having swinging arms. Second, we go into the detail on the debate whether arm swing is arising actively or passively, where we will conclude that while a large part of arm swinging is mechanically passive, there is an active contribution of muscles (i.e. an activity that is not merely caused by stretch reflexes). Third, we describe the possible function of the active muscular contribution to arm swinging in normal gait, and discuss the possibility that a Central Pattern Generator (CPG) generates this activity. Fourth, we discuss examples from pathological cases, in which arm swinging is affected. Moreover, using the ideas presented, we suggest ways in which arm swing may be used as a therapeutic aid. We conclude that (1) arm swing should be seen as an integral part of human bipedal gait, arising mostly from passive movements, which are stabilized by active muscle control, which mostly originates from locomotor circuits in the central nervous system (2) arm swinging during normal bipedal gait most likely serves to reduce energy expenditure and (3) arm swinging may be of therapeutic value.

[The interarm blood pressure difference in the critically ill patient]

BACKGROUND AND OBJECTIVE

To evaluate the prevalence of a difference in systolic blood pressure (SBPd) ≥ 10 mmHg between arms in patients admitted in a Critical Care Unit and to examine the clinical characteristics associated with such blood pressure difference.

METHODS

Observational cross-sectional study. Two blood pressure measurements in each arm were carried out at unit admission. The firstly measured arm was chosen at random.

RESULTS

One-hundred and sixty-eight patients were studied, with a mean age of 61 (SD=16), 67.3% male and 45% with a previous hypertension diagnosis. On admission, 27.4% presented SBPd ≥ 10 mmHg. Among them, 54% had higher SBP in the right arm and 46% in the left one. A SBPd ≥ 10 mmHg was associated with a previous hypertension diagnosis (67.4 versus 36.9%; P<.001) and with reduced consciousness (76.1 versus 52.5%; P=.006).

CONCLUSIONS

Over a quarter of critically ill patients have a SBPd ≥ 10 mmHg between arms. This feature is associated with a previous hypertension diagnosis and reduced consciousness. It should be assessed in the future if the choice of a control arm would help improve patient's care as it would become a more accurate guide for hemodynamic management.