scholarly journals High Load With Lower Repetitions vs. Low Load With Higher Repetitions: The Impact on Asymmetry in Weight Distribution During Deadlifting

2020 ◽  
Vol 2 ◽  
Author(s):  
Mitchel C. Whittal ◽  
Derek P. Zwambag ◽  
Luke W. Vanderheyden ◽  
Greg L. McKie ◽  
Tom J. Hazell ◽  
...  
Author(s):  
Joshua S. Lacey ◽  
Zoran S. Filipi ◽  
Sakthish R. Sathasivam ◽  
William J. Cannella ◽  
Peter A. Fuentes-Afflick

Homogeneous charge compression ignition (HCCI) combustion is highly dependent on in-cylinder thermal conditions favorable to autoignition, for a given fuel. Fuels available at the pump can differ considerably in composition and autoignition chemistry; hence strategies intended to bring HCCI to market must account for the fuel variability. To this end, a test matrix consisting of eight gasoline fuels composed of blends made solely from refinery streams was investigated in an experimental, single cylinder HCCI engine. The base compositions were largely representative of gasoline one would expect to find across the United States, although some of the fuels had slightly lower average octane values than the ASTM minimum specification of 87. All fuels had 10% ethanol by volume included in the blend. The properties of the fuels were varied according to research octane number (RON), sensitivity (S=RON-MON) and the volumetric fractions of aromatics and olefins. For each fuel, a sweep of the fuelling was carried out at each speed from the level of instability to excessive ringing to determine the limits of HCCI operation. This was repeated for a range of speeds to determine the overall operability zone. The fuels were kept at a constant intake air temperature during these tests. The variation of fuel properties brought about changes in the overall operating range of each fuel, as some fuels had more favorable low load limits, whereas others enabled more benefit at the high load limit. The extent to which the combustion event changed from the low load limit to the high load limit was examined as well, to provide a relative criterion indicating the sensitivity of HCCI range to particular fuel properties.


Author(s):  
Joshua S. Lacey ◽  
Sakthish R. Sathasivam ◽  
Zoran S. Filipi ◽  
William J. Cannella ◽  
Peter A. Fuentes-Afflick

HCCI combustion is highly dependent on in-cylinder thermal conditions favorable to auto-ignition, for a given fuel. Fuels available at the pump can differ considerably in composition and auto-ignition chemistry, hence strategies intended to bring HCCI to market must account for the fuel variability. To this end, a test matrix consisting of eight gasoline fuels composed of blends made solely from refinery streams was investigated in an experimental, single cylinder HCCI engine. The base compositions were largely representative of gasoline one would expect to find across the United States, although some of the fuels had slightly lower average octane values than the ASTM minimum specification of 87. All fuels had 10% ethanol by volume included in the blend. The properties of the fuels were varied according to research octane number (RON), sensitivity (S=RON−MON) and the volumetric fractions of aromatics and olefins. For each fuel, a sweep of the fuelling was carried out at each speed from the level of instability to excessive ringing to determine the limits of HCCI operation. This was repeated for a range of speeds to determine the overall operability zone. The fuels were kept at a constant intake air temperature during these tests. The variation of fuel properties brought about changes in the overall operating range of each fuel, as some fuels had more favorable low load limits, whereas others enabled more benefit at the high load limit. The extent to which the combustion event changed from the low load limit to the high load limit was examined as well, to provide a relative criterion indicating the sensitivity of HCCI range to particular fuel properties.


Author(s):  
Junshuai Liang ◽  
Ning Li ◽  
Jingyu Zhai ◽  
BaoGang Wen ◽  
Qingkai Han ◽  
...  

In this study, a layering method of carburized ring is presented. A finite element (FE) model for analyzing bearing stiffness characteristics is established considering the residual stress in the carburized layer. The residual stress in the carburized layer of a double-row conical roller bearing is tested and the influence of the distribution of residual stress in carburized layer on the bearing stiffness is investigated. Results show that the residual stress in the carburized layer increases the contact stiffness of the bearing by 5% in the low-load zone and 3% in the high-load zone. The radial stiffness of the bearing is increased by 5% in the low-load zone and 3% in the high-load zone. The axial stiffness is increased by 6%, and the angular stiffness increased by 4%. The larger the thickness of the carburized layer, the greater the residual compressive stress in the carburized layer, the deeper the position of the maximum residual stresses in the carburized layer will lead to the greater stiffness of the bearing.


Author(s):  
Megan J. Blakely ◽  
Kyle Wilson ◽  
Paul N. Russell ◽  
William S. Helton

The effects of physical activity on cognition and the effects of cognitive load on physical activity are complex. Both the nature of the physical activity and cognitive task may influence the interactive effects of performing a physical task while also performing a cognitive task. In a previous study examining the impact of increasing cognitive load on outdoor running speed and the impact of outdoor running on cognitive performance, Blakely et al. (2015) found running speed decreased as cognitive load increased. They also found that the impact of running itself on cognitive performance occurred when the cognitive task was itself demanding (high cognitive load). In the current study we expanded on this previous research by improving the experimental task to rule out peripheral sensory, not central or executive, interference and by incorporating heart rate measures and VO2 max estimates. Twelve runners completed five conditions, two seated cognitive tasks (one low load and one high load), two dual running cognitive tasks and one run only. Results were similar to the original experiment, as the cognitive task became more difficult, voluntary running speed decreased. Also the effects of running on cognitive performance (counting) were found only when the cognitive task was high load.


2017 ◽  
Vol 56 (6) ◽  
pp. E126-E133 ◽  
Author(s):  
Daeyeol Kim ◽  
Jeremy P. Loenneke ◽  
Xin Ye ◽  
Debra A. Bemben ◽  
Travis W. Beck ◽  
...  

2021 ◽  
pp. 014616722110443
Author(s):  
Bertram Gawronski

Research suggests that evaluations of an object can be jointly influenced by (a) the mere co-occurrence of the object with a pleasant or unpleasant stimulus (e.g., mere co-occurrence of object A and negative event B) and (b) the object’s specific relation to the co-occurring stimulus (e.g., object A starts vs. stops negative event B). Three experiments investigated the impact of cognitive load during learning on the effects of stimulus co-occurrence and stimulus relations. Counter to the shared prediction of competing theories suggesting that effects of stimulus relations should be reduced by cognitive load during learning, effects of stimulus relations were greater (rather than smaller) under high-load compared with low-load conditions. Effects of stimulus co-occurrence were not significantly affected by cognitive load. The results are discussed in terms of theories suggesting that cognitive load can influence behavioral outcomes via strategic shifts in resource allocation in response to task-specific affordances.


2021 ◽  
Vol 1 (5) ◽  
pp. 263502542110326
Author(s):  
Steven R. Dayton ◽  
Simon J. Padanilam ◽  
Tyler C. Sylvester ◽  
Michael J. Boctor ◽  
Vehniah K. Tjong

Background: Blood flow restriction (BFR) training restricts arterial inflow and venous outflow from the extremity and can produce gains in muscle strength at low loads. Low-load training reduces joint stress and decreases cardiovascular risk when compared with high-load training, thus making BFR an excellent option for many patients requiring rehabilitation. Indications: Blood flow restriction has shown clinical benefit in a variety of patient populations including healthy patients as well as those with osteoarthritis, anterior cruciate ligament reconstruction, polymyositis/dermatomyositis, and Achilles tendon rupture. Technique Description: This video demonstrates BFR training in 3 clinical areas: upper extremity resistance training, lower extremity resistance training, and low-intensity cycling. All applications of BFR first require determination of total occlusion pressure. Upper extremity training requires inflating the tourniquet to 50% of total occlusion pressure, while lower extremity exercises use 80% of total occlusion pressure. Low-load resistance training exercises follow a specific repetition scheme: 30 reps followed by a 30-second rest and then 3 sets of 15 reps with 30-seconds rest between each. During cycle training, 80% total occlusion pressure is used as the patient cycles for 15 minutes without rest. Results: Augmenting low-load resistance training with BFR increases muscle strength when compared with low-load resistance alone. In addition, low-load BFR has demonstrated an increase in muscle mass greater than low-load training alone and equivalent to high-load training absent BFR. A systematic review determined the safety of low-load training with BFR is comparable to traditional high-intensity resistance training. The most common adverse effects include exercise intolerance, discomfort, and dull pain which are also frequent in patients undergoing traditional resistance training. Severe adverse effects including deep vein thrombosis, pulmonary embolism, and rhabdomyolysis are exceedingly rare, less than 0.006% according to a national survey. Patients undergoing BFR rehabilitation experience less perceived exertion and demonstrate decreased pain scores compared with high-load resistance training. Conclusion: Blood flow restriction training is an effective alternative to high-load resistance training for patients requiring musculoskeletal rehabilitation for multiple disease processes as well as in the perioperative setting. Blood flow restriction has been shown to be a safe training modality when managed by properly trained physical therapists and athletic trainers.


Author(s):  
Amirreza Shahani ◽  
Ali Farrahi

The effect of five different stirring times of friction stir spot welding on lap-shear specimens of Al 6061-T6 alloy has been experimentally analyzed. The welding condition with 2 s of stirring shows the optimum mechanical behavior in comparison to the others. The static strength and fatigue behavior of the joint are justified using the microhardness profiles. The static results prove that the increase of stirring time beyond the 2 s case has little effect on improving the static strength. The fatigue results reveal two different failure modes, which are shear fracture at high load levels and transverse crack growth at low load levels. At medium load levels, although the final failure is similar to high load levels, the transverse growth of the crack outside the welding zone, just like low load levels, is also observed.


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