Carrying Asymmetric Loads While Walking on a Treadmill Interferes with Lower Limb Coordination

The purpose of this study was to investigate the effect of different load carriage modes on coordinative patterns in the lower extremities during walking. Twenty-five university students walked on a treadmill at their preferred pace under three different load conditions: symmetric load (5% of body mass in messenger bags on each shoulder hanging vertically and against the hips), asymmetric load 1 (10% of body mass in a messenger bag on one shoulder hanging vertically against the ipsilateral hip), and asymmetric load 2 (10% of body mass in a messenger bag on one shoulder with the bag draped across the trunk to the contralateral hip). Altered thigh-shank and shank-foot couplings were found for the loaded side during the stance of gait when comparing the asymmetric 1 and 2 to the symmetric load. In addition, thigh-thigh coupling was changed during gait when comparing the asymmetric load 2 and symmetric load. However, we did not find any significant differences in intralimb and interlimb couplings between the two different asymmetric load conditions. The results suggest potential benefits when carrying symmetrical loads in order to decrease abnormal limb coordination in daily activities. Thus, it may be advisable to distribute load more symmetrically to avoid abnormal gait.

Lateral Deformation Characteristics and Control Methods of Foundation Pits Subjected to Asymmetric Loads

Using the foundation pit at the Jianye Road Station of Hangzhou Metro Line 6 as a case study, the deformation characteristics of a foundation pit subjected to asymmetric loads is investigated in this paper using PLAXIS 3D numerical simulation software. The influence of active pressure zone reinforcement, passive pressure zone reinforcement, and increased thickness of the diaphragm wall at the loaded side on the maximum lateral displacement of diaphragm wall retaining structure of foundation pit is also systematically analyzed. The results show that the deformation of the diaphragm walls on both sides of the foundation pit is strongly inconsistent when subjected to asymmetric loads and is affected by the asymmetric load value and its distance to the foundation pit. In order to reduce the lateral deformations of foundation pit subjected to asymmetric load, two displacement control methods are adopted in the numerical simulations. It is shown that reinforcing the active pressure zone can reduce the maximum lateral displacement of the diaphragm wall on the loaded side to a certain extent but the reinforcement should have a certain depth, resulting in poor efficiency. On the other hand, reinforcing the passive pressure zone can effectively reduce the difference in lateral deformation between the two sides of the foundation pit by increasing the depth and width of the reinforcement zones. It is also observed that the increase in the thickness of the diaphragm wall can reduce the adverse effect of asymmetric loads on the foundation pit. The research results can provide reference for using measures to reduce the influence of asymmetric loads.

Muscle activity in asymmetric bench press among resistance-trained individuals

Purpose To determine the effects of asymmetric loads on muscle activity with the bench press. Method Seventeen resistance-trained men performed one familiarization session including testing one repetition maximum (1RM) and three 5 repetition maximum (RM) lifts; using symmetric loads, 5% asymmetric loads, and 10% asymmetric loads. The asymmetric loading (i.e., reduced load on one side) was calculated as 5% and 10% of the subject`s 1RM load. In the experimental session, the three conditions of 5RM were conducted with electromyographic activity from the pectoralis major, triceps brachii, biceps brachii, anterior deltoid, posterior deltoid, and external oblique on both sides of the body. Results On the loaded side, asymmetric loads reduced triceps brachii activation compared to symmetric loads, whereas the other muscles demonstrated similar muscle activity between the three conditions. On the de-loaded side, 10% asymmetry in loading resulted in lower pectoralis major, anterior deltoid, and biceps brachii activation compared to 5% asymmetric and symmetric loading. On the de-loaded side, only pectoralis major demonstrated lower muscle activation than symmetric loads. Furthermore, asymmetric loads increased external oblique activation on both sides compared to symmetric loads. Conclusions Asymmetric bench press loads reduced chest and shoulder muscle activity on the de-loaded side while maintaining the muscle activity for the loaded side. The authors recommend resistance-trained participants struggling with strength imbalances between sides, or activities require asymmetric force generation (i.e., alpine skiing or martial arts), to implement asymmetric training as a supplement to the traditional resistance training.

Standing on a Double-Seesaw Device is an Easy Way to Modify the Coordination Between the Two Feet for Controlling Upright Stance: Assessment Through Weight-Bearing Asymmetry

Healthy young subjects were instructed to modify their weight-bearing asymmetry when standing on a double-seesaw device. The results indicated decreased and unchanged amplitudes in the center-of-pressure movements under the unloaded and loaded legs, respectively. In addition, a concomitant increased contribution of the more loaded leg and a decreased contribution of the pressure distribution mechanism along the mediolateral axis were observed in the production of the resultant center of pressure, its amplitude remaining constant. Thus, contrary to what was previously reported for stance control on solid ground, one of the main characteristics of a double-seesaw device, by preventing increased amplitudes on the loaded side during weight-bearing asymmetry, would be to facilitate a greater independency of the feet in the stance control process.

Changes in Muscle Pattern Activity during the Asymmetric Flat Bench Press (Offset Training)

Background: This study aimed to compare the muscle activity between the symmetric and selected asymmetric loads (2.5%; 5% and 7.5% differences in load position between sides of the bar) during the flat bench press (BP) exercise at 70%1RM. The study included 10 resistance-trained males (25.3 ± 2.3 years; 82.9 ± 6.9 kg; 177.8 ± 4.5 cm; 1RM BP: 104.5 ± 8.6 kg; experience: 5.6 ± 1.5 years). Methods: To assess the differences in muscle activity between both sides of the body and load placement, the participants performed several attempts of the BP with symmetric and asymmetric load at 70%1RM in a random order (symmetric; 2.5%; 5% and 7.5% differences in load position between sides of the bar). Peak muscle activity of dominant and non-dominant body-side was recorded for the pectoralis major (PM), anterior deltoid (AD), and the long head of the triceps brachii (TB). Results: A two-way repeated-measures analysis of variance (ANOVA) indicated a statistically significant main interaction between side and load (p < 0.01) for AD, PM and TB muscles. Conclusion: The results of this study showed that asymmetrically loaded BP leads to significantly higher muscle activity on the loaded side of the body. The offset training method during bilateral resistance exercise may be an effective and simple approach for reductions in muscle imbalances and improvement in bilateral exercise performance.

Generation and Experimental Stress Analysis of Elliptical Gears with Combined Teeth

In this study, generation of elliptical gears with different teeth profiles of crowned involute, double circular arc (DCA), and combined (crowned involute with DCA) has been developed. The resulting mathematical equations have been computerized and feed to CNC end mill machine to manufacture elliptical gear models with different profiles. These models are investigated in plane polariscope to show the resulting stresses under certain load. Comparison of photo-elastic stress results shows that combined elliptical gears with DCA side as a loaded side have a minimum resulting contact stress with a reduction percentage of 40% compare with contact stresses in counterpart elliptical gear of involute profile (which is commonly used in several applications). In this case, bending tooth stress reduction is 47.05% compare with involute elliptical gear. While the reduction in bending stresses of combined elliptical gear becomes higher (52.94% lower than involute gear) when crowned involute side is the loaded side, but the contact stress reduction in this case becomes lower (20% relative to involute gear). Maximum reduction in bending stress can be obtained when single profile of DCA type is used with a reduction of 64.7% relative to involute gear. Therefore; when the application requires a high contact stress resistance, combined profile can be used with DCA side as a loaded side. While in the applications that require high bending stress resistance, DCA profile can be used.

Analysis of muscle tone distribution in premature babies based on PodoBaby podoscope examination

Introduction: The aim of the study was to assess load surface with regard to muscle tone distribution of premature infants compared to full-term infants. Material and methods: Twenty-four infants aged 3-6 months (adjusted age) were examined, including 12 premature infants (born before 37 weeks) and 12 full-term infants. The study was carried out at the Children’s Memorial Health Institute in Warsaw in the period from January to June 2016. The study involved interviews with the infants’ parents and examinations of infants in a supine and prone position performed on PodoBaby digital podoscope. Support surface, i.e. the loading on the left and right side of the body and the length of trunk sides were analysed. Statistical analysis was performed with the use of Statistica v.12 software and Student’s t-test. Results: No significant differences between premature infants and full-term infants regarding the loading on the right side measured in a supine position were revealed (analogous lack of differences was noted on the left side and in a prone position). In a prone position, the correlation between support surface and the length of trunk sides was noted, i.e. the loaded side of the trunk was lengthened, while the unloaded side was shortened. Conclusions: Considerable asymmetry of the loads of trunk sides was noted in premature infants, while in the case of full-term infants, the values of loads were close to symmetry. An examination with the use of PodoBaby podoscope may be applied in early diagnostics in pediatric rehabilitation.

Modelling and Analysis of Elastic and Thermal Deformations of a Hydrodynamic Radial Journal Bearing

Journal bearings are widely used in heavy industry and in internal combustion engine applications. There is a need to increase the power density of various machine parts which leads to increased bearing loads and reduced lubrication film thicknesses. This type of development may increase deformations on the bearing surfaces which need to be considered in the bearing design process.The main purpose of this work was to develop a parameterized calculation model for hydrodynamic radial journal bearings which takes into account elastic and thermal deformations of the bearing surfaces. Hydrodynamic calculations were based on the numerical solving of the Reynolds equation by assuming rigid surfaces. Elastic and thermal deformations of the bearing and shaft surfaces were calculated by using the finite element method. It is concluded that elastic and thermal deformations are partly canceling each other out at the loaded side of the bearing and depending on the sliding speed and the external normal force either one of them could be more significant.