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PeerJ 2022Progressive overload is a principle of resistance training exercise program design that typically relies on increasing load to increase neuromuscular demand to... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Progressive overload is a principle of resistance training exercise program design that typically relies on increasing load to increase neuromuscular demand to facilitate further adaptations. However, little attention has been given to another way of increasing demand-increasing the number of repetitions.
OBJECTIVE
This study aimed to compare the effects of two resistance training programs: (1) increasing load while keeping repetition range constant (2) increasing repetitions while keeping load constant. We aimed to compare the effects of these programs on lower body muscle hypertrophy, muscle strength, and muscle endurance in resistance-trained individuals over an 8-week study period.
METHODS
Forty-three participants with at least 1 year of consistent lower body resistance training experience were randomly assigned to one of two experimental, parallel groups: A group that aimed to increase load while keeping repetitions constant (LOAD: = 22; 13 men, nine women) or a group that aimed to increase repetitions while keeping load constant (REPS: = 21; 14 men, seven women). Subjects performed four sets of four lower body exercises (back squat, leg extension, straight-leg calf raise, and seated calf raise) twice per week. We assessed one repetition maximum (1RM) in the Smith machine squat, muscular endurance in the leg extension, countermovement jump height, and muscle thickness along the quadriceps and calf muscles. Between-group effects were estimated using analyses of covariance, adjusted for pre-intervention scores and sex.
RESULTS
Rectus femoris growth modestly favored REPS (adjusted effect estimate (CI), sum of sites: 2.8 mm [-0.5, 5.8]). Alternatively, dynamic strength increases slightly favored LOAD (2.0 kg [-2.4, 7.8]), with differences of questionable practical significance. No other notable between-group differences were found across outcomes (muscle thicknesses, <1 mm; endurance, <1%; countermovement jump, 0.1 cm; body fat, <1%; leg segmental lean mass, 0.1 kg), with narrow CIs for most outcomes.
CONCLUSION
Both progressions of repetitions and load appear to be viable strategies for enhancing muscular adaptations over an 8-week training cycle, which provides trainers and trainees with another promising approach to programming resistance training.
Topics: Male; Humans; Female; Muscle, Skeletal; Quadriceps Muscle; Resistance Training; Muscle Strength; Leg
PubMed: 36199287
DOI: 10.7717/peerj.14142 -
Sports Medicine - Open Nov 2023Many perform resistance training (RT) to increase muscle mass and strength. Energy surpluses are advised to support such gains; however, if too large, could cause...
BACKGROUND
Many perform resistance training (RT) to increase muscle mass and strength. Energy surpluses are advised to support such gains; however, if too large, could cause unnecessary fat gain. We randomized 21 trained lifters performing RT 3 d/wk for eight weeks into maintenance energy (MAIN), moderate (5% [MOD]), and high (15% [HIGH]) energy surplus groups to determine if skinfold thicknesses (ST), squat and bench one-repetition maximum (1-RM), or biceps brachii, triceps brachii, or quadriceps muscle thicknesses (MT) differed by group. COVID-19 reduced our sample, leaving 17 completers. Thus, in addition to Bayesian ANCOVA comparisons, we analyzed changes in body mass (BM) with ST, 1-RM, and MT changes via regression. We reported Bayes factors (BF) indicating odds ratios of the relative likelihood of hypotheses (e.g., BF = 2 indicates the hypothesis is twice as likely as another) and coefficients of determination (R) for regressions.
RESULTS
ANCOVAs provided no evidence supporting the group model for MT or squat 1-RM. However, moderate (BF = 9.9) and strong evidence (BF = 14.5) indicated HIGH increased bench 1-RM more than MOD and MAIN, respectively. Further, there was moderate evidence (BF = 4.2) HIGH increased ST more than MAIN and weak evidence (BF = 2.4) MOD increased ST more than MAIN. Regression provided strong evidence that BM change predicts ST change (BF = 14.3, R = 0.49) and weak evidence predicting biceps brachii MT change (BF = 1.4, R = 0.24).
CONCLUSIONS
While some group-based differences were found, our larger N regression provides the most generalizable evidence. Therefore, we conclude faster rates of BM gain (and by proxy larger surpluses) primarily increase rates of fat gain rather than augmenting 1-RM or MT. However, biceps brachii, the muscle which received the greatest stimulus in this study, may have been positively impacted by greater BM gain, albeit slightly. Our findings are limited to the confines of this study, where a group of lifters with mixed training experience performed moderate volumes 3 d/wk for 8 weeks. Thus, future work is needed to evaluate the relationship between BM gains, increases in ST and RT adaptations in other contexts.
PubMed: 37914977
DOI: 10.1186/s40798-023-00651-y -
Materials (Basel, Switzerland) Dec 2022P-type SbTe films with different thicknesses were deposited on polyimide substrates via heat treatment-assisted DC magnetron sputtering. The correlations between the...
P-type SbTe films with different thicknesses were deposited on polyimide substrates via heat treatment-assisted DC magnetron sputtering. The correlations between the thickness variance and the structure, dislocation density, surface morphology, thermoelectric properties and output power are investigated. As a result, it is clear that the film thickness and the heat treatment process during growth are related to the diffusion of deposited atoms on the substrate surface, leading to imperfection defects inside the films. The imperfections inside the films are affected by their properties. This work also presents the thermoelectric efficiency of a planar single leg of the deposited films with various thicknesses. The maximum power factor is 2.73 mW/mK obtained with a film thickness of 9.0 µm and an applied temperature of 100 °C. Planar SbTe produced a maximum output power of 0.032 µW for a temperature difference of 58 K.
PubMed: 36556656
DOI: 10.3390/ma15248850 -
Frontiers in Bioengineering and... 2021Orthokeratology has been widely used to control myopia, but the mechanism is still unknown. To further investigate the underlying mechanism of corneal reshaping using...
Orthokeratology has been widely used to control myopia, but the mechanism is still unknown. To further investigate the underlying mechanism of corneal reshaping using orthokeratology lenses the finite element method, numerical models with different corneal curvatures, corneal thicknesses, and myopia reduction degrees had been developed and validated to simulate the corneal response and quantify the changes in maximum stress in the central and peripheral corneal areas during orthokeratology. The influence of the factors on corneal response had been analyzed by using median quantile regression. A partial eta squared value in analysis of variance models was established to compare the effect size of these factors. The results showed central and peripheral corneal stress responses changed significantly with increased myopia reduction, corneal curvature, and corneal thickness. The target myopia reduction had the greatest effect on the central corneal stress value (partial eta square = 0.9382), followed by corneal curvature (partial eta square = 0.5650) and corneal thickness (partial eta square = 0.1975). The corneal curvature had the greatest effect on the peripheral corneal stress value (partial eta square = 0.5220), followed by myopia reduction (partial eta square = 0.2375) and corneal thickness (partial eta square = 0.1972). In summary, the biomechanical response of the cornea varies significantly with the change in corneal conditions and lens designs. Therefore, the orthokeratology lens design and the lens fitting process should be taken into consideration in clinical practice, especially for patients with high myopia and steep corneas.
PubMed: 34708026
DOI: 10.3389/fbioe.2021.743745 -
Evidence-based Complementary and... 2022Warm-needle acupuncture (WA) and fire-needle acupuncture are treatment techniques that use the combination of acupuncture and thermal stimulation. In clinical practice,...
BACKGROUND
Warm-needle acupuncture (WA) and fire-needle acupuncture are treatment techniques that use the combination of acupuncture and thermal stimulation. In clinical practice, a new method of fire-needle acupuncture called "heated-needle acupuncture (HA)" has been proposed, wherein the needle is directly heated after insertion. WA and HA share similarities in their methods, and no previous study has sought to assess whether their thermal outcomes are also similar.
METHODS
We controlled environmental variables and measured the maximum temperatures and temperature changes of a silicon phantom in which K-type thermocouples were embedded at depths of 0, 2, 5, 7, and 10 mm. WA and HA were also performed with acupuncture needles of various thicknesses (0.30 × 40 mm, 0.40 × 40 mm, and 0.50 × 40 mm).
RESULTS
Different time-dependent temperature distributions were observed between the two acupuncture methods: HA yielded a higher maximum temperature and temperature change on the surface, whereas WA yielded higher temperatures at the other tested depths. The thermal patterns were similar among the needles of different thicknesses for each method, with the following exception: while the temperature change and maximum temperature did not differ significantly by needle thickness for WA, these parameters increased significantly with needle thickness for HA.
CONCLUSION
The two acupuncture procedures yielded different thermal patterns in a controlled environment. Further studies are necessary to reflect the effect of external environment variables occurring in reality.
PubMed: 35265145
DOI: 10.1155/2022/4159172 -
ACS Nano Nov 2020The structure of neat melts of polymer-grafted nanoparticles (GNPs) is studied coarse-grained molecular dynamics simulations. We systematically vary the degree of...
The structure of neat melts of polymer-grafted nanoparticles (GNPs) is studied coarse-grained molecular dynamics simulations. We systematically vary the degree of polymerization and grafting density at fixed nanoparticle (NP) radius and study in detail the shape and size of the GNP coronas. For sufficiently high grafting density, chain sections close to the NP core are extended and form a dry layer. Further away from the NP, there is an interpenetration layer, where the polymer coronas of neighboring GNPs overlap and the chain sections have almost unperturbed conformations. To better understand this partitioning, we develop a two-layer model, representing the grafted polymer around an NP by spherical dry and interpenetration layers. This model quantitatively predicts that the thicknesses of the two layers depend on one universal parameter, , the degree of overcrowding of grafted chains relative to chains in the melt. Both simulations and theory show that the chain extension free energy is nonmonotonic with increasing chain length at a fixed grafting density, with a well-defined maximum. This maximum is indicative of the crossover from the dry layer-dominated to interpenetration layer-dominated regime, and it could have profound consequences on our understanding of a variety of anomalous transport properties of these GNPs. Our theoretical approach therefore provides a facile means for understanding and designing solvent-free GNP-based materials.
PubMed: 33084300
DOI: 10.1021/acsnano.0c06134 -
Eye (London, England) May 2020To characterize and evaluate the use of corneal epithelial profile maps generated by an ultrahigh-resolution optical coherence tomography (UHR-OCT) in the diagnosis and...
BACKGROUND/OBJECTIVES
To characterize and evaluate the use of corneal epithelial profile maps generated by an ultrahigh-resolution optical coherence tomography (UHR-OCT) in the diagnosis and management of dry-eye disease (DED).
SUBJECTS/METHODS
This prospective, interventional case-control study included 115 eyes of 71 subjects (52 DED and 19 controls) imaged using an UHR-OCT. Average, maximum, and minimum, range of corneal epithelial thicknesses were extracted from epithelial profile maps. Surface regularity was quantified using the range and variance of the epithelial thickness measured along a horizontal UHR-OCT scan. The variance of thickness measurements along a scan was named epithelial irregularity factor (EIF). Symptoms of 31 DED patients (55 eyes) were quantified by questionnaire and correlated to epithelial profile findings, fluorescein staining, tear breakup time, and Schirmer's test. Twenty-one DED eyes were administered autologous serum drops and follow-up UHR-OCT images were captured.
RESULTS
DED patients had a highly irregular corneal epithelial surface compared with controls. Epithelial thickness profile variance (EIF) and range were significantly higher in DED as compared with controls (5.79 vs. 0.77, p < 0.001 and 7.6 vs. 4.6 μm, p < 0.001). Both parameters were highly significantly correlated with questionnaire scores (EIF: r = 0.778; p < 0.001, range: r = 0.737; p < 0.001). Follow-up showed a statistically significant reduction in epithelial thickness profile variance and range of treated patients ( p < 0.001).
CONCLUSIONS
DED patients have irregular epithelial surface that can be quantified using UHR-OCT generated CEP maps. Epithelial thickness profile range and EIF correlate accurately with patients' symptoms and could be used to follow-up patients and response to treatment.
Topics: Case-Control Studies; Cornea; Dry Eye Syndromes; Humans; Prospective Studies; Tears; Tomography, Optical Coherence
PubMed: 31576026
DOI: 10.1038/s41433-019-0592-y -
Journal of the Mechanical Behavior of... Jan 2022In order to determine a suitable thickness of polyetheretherketone (PEEK) for manufacturing of surgical membranes, the purpose was to evaluate how different thicknesses...
In order to determine a suitable thickness of polyetheretherketone (PEEK) for manufacturing of surgical membranes, the purpose was to evaluate how different thicknesses of PEEK influence the mechanical properties under flexure and tension. In total 20 specimens in PEEK with two different thicknesses, 0.5 mm and 1.0 mm were fabricated and tested in a three-point flexural strength test and tensile strength test (n = 5 specimens). Statistical analysis was done with non-parametric Mann-Whitney test with level of significance α = 0.05, for both material tests, respectively. The 1.0 mm-thick samples resulted in higher values in elastic limit and conventional deflection (S-value) in the flexural strength test compared to 0.5 mm-thick samples. In the tensile strength test, the results did not show any significant difference in elastic limit depending on the thickness evaluated. However, PEEK with thickness of 1.0 mm received significantly higher maximum value at fracture. Within the limitations of this study, PEEK with a thickness of 0.5 mm-1.0 mm shows mechanical properties that are appropriate thickness and can meet the complex demands for dimensioning of surgical membranes.
Topics: Benzophenones; Biocompatible Materials; Polymers
PubMed: 34736026
DOI: 10.1016/j.jmbbm.2021.104928 -
International Journal of Molecular... Nov 2022Magnetically soft-soft MnFeO-FeO core-shell nanoparticles were synthesized through a seed-mediated method using the organometallic decomposition of metal acetyl...
Magnetically soft-soft MnFeO-FeO core-shell nanoparticles were synthesized through a seed-mediated method using the organometallic decomposition of metal acetyl acetonates. Two sets of core-shell nanoparticles (S1 and S2) of similar core sizes of 5.0 nm and different shell thicknesses (4.1 nm for S1 and 5.7 nm for S2) were obtained by changing the number of nucleating sites. Magnetic measurements were conducted on the nanoparticles at low and room temperatures to study the shell thickness and temperature dependence of the magnetic properties. Interestingly, both core-shell nanoparticles showed similar saturation magnetization, revealing the ineffective role of the shell thickness. In addition, the coercivity in both samples displayed similar temperature dependencies and magnitudes. Signatures of spin glass (SG) like behavior were observed from the field-cooled temperature-dependent magnetization measurements. It was suggested to be due to interface spin freezing. We observed a slight and non-monotonic temperature-dependent exchange bias in both samples with slightly higher values for S2. The effective magnetic anisotropy constant was calculated to be slightly larger in S2 than that in S1. The magnetothermal efficiency of the chitosan-coated nanoparticles was determined by measuring the specific absorption rate (SAR) under an alternating magnetic field (AMF) at 200-350 G field strengths and frequencies (495.25-167.30 kHz). The S2 nanoparticles displayed larger SAR values than the S1 nanoparticles at all field parameters. A maximum SAR value of 356.5 W/g was obtained for S2 at 495.25 kHz and 350 G for the 1 mg/mL nanoparticle concentration of ferrogel. We attributed this behavior to the larger interface SG regions in S2, which mediated the interaction between the core and shell and thus provided indirect exchange coupling between the core and shell phases. The SAR values of the core-shell nanoparticles roughly agreed with the predictions of the linear response theory. The concentration of the nanoparticles was found to affect heat conversion to a great extent. The in vitro treatment of the MDA-MB-231 human breast cancer cell line and HT-29 human colorectal cancer cell was conducted at selected frequencies and field strengths to evaluate the efficiency of the nanoparticles in killing cancer cells. The cellular cytotoxicity was estimated using flow cytometry and an MTT assay at 0 and 24 h after treatment with the AMF. The cells subjected to a 45 min treatment of the AMF (384.50 kHz and 350 G) showed a remarkable decrease in cell viability. The enhanced SAR values of the core-shell nanoparticles compared to the seeds with the most enhancement in S2 is an indication of the potential for tailoring nanoparticle structures and hence their magnetic properties for effective heat generation.
Topics: Humans; Hyperthermia, Induced; Ferric Compounds; Nanoparticles; Magnetic Fields
PubMed: 36499152
DOI: 10.3390/ijms232314825 -
Investigative Ophthalmology & Visual... Feb 2023To determine whether lens mechanical dynamics change with age and with accommodative demands.
PURPOSE
To determine whether lens mechanical dynamics change with age and with accommodative demands.
METHODS
Lens thickness microfluctuations were measured using a high-speed custom-built spectral domain optical coherence tomography system in five young adults (20 to 25 years old) at 0 diopters (D), 2 D, 4 D, and maximum accommodative demand and in five prepresbyopes (38 to 45 years old) under relaxed and maximal accommodation. For each state, the measurements were repeated four times during the same session. Images of the central 2-mm zone of the lens comprising 170 A-lines/frame were acquired for 10 seconds, and axial lens thickness change was measured. Lens thickness microfluctuations (µm²/Hz) were assessed by integrating the power spectrum of lens thickness microfluctuations between 0 and 4 Hz.
RESULTS
The amplitude of lens microfluctuations was higher in the accommodated states than in the relaxed state in both age groups. Lens microfluctuations were higher in young adult participants than in prepresbyopes, with a significant difference in relaxed and maximally accommodated states (P = 0.04 and P = 0.04). In the young participants, the amplitude of microfluctuations reached a plateau at maximum accommodation.
CONCLUSIONS
Lens mechanical dynamics are both age and accommodation dependent. The decrease in lens thickness microfluctuations with age is consistent with an age-related increase in lens stiffness or decrease of the ciliary muscle displacement. The lens does not contribute to the high-frequency component of ocular dioptric microfluctuations.
Topics: Young Adult; Humans; Adult; Middle Aged; Accommodation, Ocular; Lens, Crystalline; Ciliary Body
PubMed: 36753168
DOI: 10.1167/iovs.64.2.12