High-load Resistance Research Articles

Architecture of an efficient dual band 1.8/2.5 GHz rectenna for RF energy harvesting

This paper presents a highly efficient rectenna of RF energy harvesting systems operating at 1.8 GHz and 2.5 GHz bands for battery-less sensor application. The antenna is designed by CST-MWS. The Schottky diode used for rectifying circuit is HSMS 286B in which designed by Agilent ADS. The key finding of the paper is that the simulated DC output voltage of the rectenna is 1.35 V for low input power of -25 dBm at a high resistance load of 1M Ω. Correspondingly, the RF-DC conversion efficiency of the rectification process is 59.51% and 45.75% at 1.8 GHz and 2.5 GHz, which are high efficiency and much better compared to literature respectively. The rectenna is capable to produce 1.8 V from an input power of -20 dBm. Thus, the proposed RF energy harvesting system offers a promising solution designed for efficient functionality at a low power level of RF energy in the dual band.

Blood flow restriction - short insight of the method

Abstract Introduction: The blood flow restriction method is a training method that is based on the partial occlusion of circulation during a workout. This technique combines low-intensity exercise with the occlusion of the bloodstream which produces results similar to high-intensity training. Aim: We aimed to identify the areas in which this method is applicable, its potential benefits and effects, recommendations regarding the rules of use for maximal effects (dosage, intensity, etc.), and also possible contraindications or warnings regarding the use of this method. Methods: We have analyzed a number of 20 articles on this topic from the field literature of the last 10 years, using ”google academic” as a search engine. Results: After this study we concluded that blood flow restriction is a method with wide applicability in the field of sports training, but also in the recovery process; however, it requires attention in choosing the necessary equipment. For healthy individuals, best training adaptations occur when combining low-load blood flow restriction resistance exercise with traditional high-load resistance exercise. Conclusion: Low-intensity resistance exercise with blood flow restriction is as effective as high-intensity training (for strength and muscle mass gains), but only the high-intensity protocol promotes significant hypotensive responses after exercise.

Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training.

Low-load blood flow restriction (LL-BFR) training has gained increasing interest in the scientific community by demonstrating that increases in muscle mass and strength are comparable to conventional high-load (HL) resistance training. Although adaptations on the muscular level are well documented, there is little evidence on how LL-BFR training affects human myotendinous properties. Therefore, the aim of the present study was to investigate morphological and mechanical Achilles tendon adaptations after 14 wk of strength training. Fifty-five male volunteers (27.9 ± 5.1 yr) were randomly allocated into the following three groups: LL-BFR [20-35% of one-repetition maximum (1RM)], HL (70-85% 1RM), or a nonexercising control (CON) group. The LL-BFR and HL groups completed a resistance training program for 14 wk, and tendon morphology, mechanical as well as material properties, and muscle cross-sectional area (CSA) and isometric strength were assessed before and after the intervention. Both HL (+40.7%) and LL-BFR (+36.1%) training induced significant increases in tendon stiffness (P < 0.05) as well as tendon CSA (HL: +4.6%, LL-BFR: +7.8%, P < 0.001). These changes were comparable between groups without significant changes in Young's modulus. Furthermore, gastrocnemius medialis muscle CSA and plantar flexor strength significantly increased in both training groups (P < 0.05), whereas the CON group did not show significant changes in any of the evaluated parameters. In conclusion, the adaptive change in Achilles tendon properties following low-load resistance training with partial vascular occlusion appears comparable to that evoked by high-load resistance training.NEW & NOTEWORTHY Low-load blood flow restriction (LL-BFR) training has been shown to induce beneficial adaptations at the muscular level. However, studies examining the effects on human tendon properties are rare. The findings provide first evidence that LL-BFR can increase Achilles tendon mechanical and morphological properties to a similar extent as conventional high-load resistance training. This is of particular importance for individuals who may not tolerate heavy training loads but still aim for improvements in myotendinous function.

Moderate vs high-load resistance training on muscular adaptations in rats

AimsThe main aim of this study was to investigate the moderate versus high-load resistance training on muscle strength, hypertrophy and protein synthesis signaling in rats. MethodsTwenty rats were randomly allocated into three groups as follow: control group (C, n = 6), high-load training (HL, n = 7) and moderate-load training (ML, n = 7). A ladder climb exercise was used to mimic resistance exercise. ML resistance training consisted of a moderate load, allowing performance at higher volume of load inherent to higher number of repetitions (8-16 climbing). HL resistance training consisted of progressively increase training load, with low volume of load (4-8 climbing). C group remained with physical activity restricted to their cage space. This experiment was conducted over a six-weeks period. Forty-eight hours after the last resistance training session the animals were euthanized for tissue collection. ResultsBoth HL and ML regimens promoted similar increases in muscle strength, elevated protein synthesis signaling demonstrated by increased skeletal muscle total/phosphorylated P-70S6K ratio and similar increases in plantaris and FHL muscle hypertrophy, all compared to control. All these similarities were demonstrated even though testosterone/cortisol ratio was higher in HL group compared to ML and control. ML regimen caused higher total training volume and soleus muscle hypertrophy, which was not demonstrated in HL group. ConclusionIn conclusion, results suggest that both HL and ML induce muscle hypertrophy and increase on strength in a similar way. ML moreover seems to favor slow fiber hypertrophy due the higher training volume.

THE EFFICACY AND VALIDITY OF BLOOD FLOW RESTRICTION TRAINING IN CLINICAL AND POST-SURGICAL POPULATIONS

Background: We currently know BFR training is a viable modality for strength gains in the healthy population. However, it is unknown the effect of BFR training on post-surgical and clinical populations. Furthermore, the optimal use of the BFR modality regarding resistance vs. no-resistance (bodyweight) is also unknown. This literature review adds new information to the field of BFR training specifically in the post-surgical and clinical populations. The objective of the study is to explore the validity and efficacy of blood-restriction training (BFR) in conjunction with low-load resistance training (LL-BFR) versus low-load training without BFR and high-load resistance training without BFR to determine which is superior for strength gains.Methods: The authors used SPORTDiscus, EBSCO, PubMed, and Science Direct to search for peer-reviewed articles. The articles chosen had the keywords/phrases “BFR,” “vascular occlusion,” “strength training,” “resistance training.” The studied emphasized patients with either clinical conditions (osteoarthritis) or musculoskeletal injuries (ACL reconstruction, total knee arthroplasty, knee arthroscopy). One hundred seventy-one articles were screened, and 17 articles reviewed.Results: BFR, in conjunction with low-load resistance training yields superior strength gains when compared to lowload training alone (p<.05). The outcome measures show a higher 1-rep max (isotonic strength) and greater muscle size (cross-sectional area, muscle mass, muscle volume) (p<.05). However, BFR with low-load resistance training does not yield superior strength gains in comparison to high-load resistance training alone (p<.03).Conclusion: As healthcare providers treating patients with musculoskeletal conditions, we know the importance of resistance training as a tool for rehabilitation and activities of daily living. However, at times heavy resistance training is contraindicated either due to joint instability/degeneration, pain, surgical restrictions. BFR training can be implemented with a 10-30% 1-rep max for comparable strength gains. This can be a potential tool used to offset post-surgical atrophy and atrophy due to arthralgia seen in certain systemic conditions. This can translate to better functional outcomes in post-surgical patients and superior quality of life in the geriatric population.

Low-Load vs. High-Load Resistance Training to Failure on One Repetition Maximum Strength and Body Composition in Untrained Women: Addendum.

Journal of Strength and Conditioning Research: October 2019 - Volume 33 - Issue 10 - p e227 doi: 10.1519/JSC.0000000000003319

Hunger is suppressed after resistance exercise with moderate-load compared to high-load resistance exercise: the potential influence of metabolic and autonomic parameters

The purpose of present study was to compare the effects of moderate-load versus high-load resistance exercise (RE) on hunger response, blood lactate, glucose, and autonomic modulation in trained men, and to examine the correlations between these parameters. For this, 11 recreationally resistance-trained males performed 2 randomized trials: moderate-load (6 sets at 70% 1-repetition maximum (1RM) and a 90-s rest interval between sets) and high-load (6 sets at 90% 1RM and a 180-s rest interval between sets) leg-press exercise until movement failure. The subjective rating of hunger was obtained through a visual analog scale. Glucose and lactate concentration were evaluated at rest, immediately after exercise, and 30 min after exercise. Heart rate variability was recorded at baseline and during recovery (until 30 min after exercise) to assess autonomic modulation. The moderate-load condition induced lower subjective hunger ratings than the strength condition immediately after exercise (19.7 ± 16.6 vs 47.3 ± 27.7 mm), 30 min after exercise (33.6 ± 22.9 vs 58.5 ± 29.9 mm), and 60 min after exercise (43.8 ± 26.6 vs 67.8 ± 27.9 mm) (p < 0.05) and lower area under the curve hunger in relation to the high-load condition (p < 0.006). Moderate-load RE presented greater lactate concentration and induced slower heart rate variability recovery in relation to high-load RE (p < 0.05), but no difference was found in glucose, as well as no correlations between any of the variables investigated. In conclusion, moderate-load RE induced lower subjective hunger ratings, slower recovery of the parasympathetic nervous system, and higher lactate concentration in relation to high-load RE, but the metabolic variables were not correlated with hunger suppression.

Is low load blood flow restriction training an effective intervention in improving clinical outcomes in adults with lower extremity pathology: a systematic review

Background: Blood flow restriction (BFR) is a safe and effective method of muscle strengthening that involves placing a tourniquet on a limb to occlude venous blood. This reduces the amount of oxygen and produces an anaerobic environment in the muscle, thus producing hypertrophy in the muscle.Objective: The primary purpose of this systematic review was to determine whether low load BFR training impacts functional outcomes and is effective when rehabilitating patients with lower extremity pathology.Methods: Balance, gait speed/endurance, functional strength, and mobility/fall risk was assessed while self-reported outcome measures assessed general health, pain with function, and function. All studies compared low load BFR to high load resistance training. A total of 3264 articles were reviewed and five RCTs met the inclusion criteria and were included in this analysis.Results: Participants’ ages ranged from 18 to 70 years old and sample sizes ranged from 17 to 69 participants. Results demonstrated significant changes from baseline in all outcomes with BFR.Conclusion: Low load BFR training can produce significant improvement in both functional and self-reported outcomes; however, it did not show that low load BFR was a better and more effective treatment when compared to high-load resistance training.

Blood flow restriction in human skeletal muscle during rest periods after high-load resistance training down-regulates miR-206 and induces Pax7

BackgroudBlood flow restriction (BFR) with low-intensity resistance training has been shown to result in hypertrophy of skeletal muscle. In this study, we tested the hypothesis that BFR during the rest periods between acute, high-intensity resistance exercise sessions (70% of 1 repetition maximum, 7 sets with 10 repetitions) enhances the effects of the resistance training. MethodsA total of 7 healthy young men performed squats, and between sets BFR was carried out on one leg while the other leg served as a control. Because BFR was applied during rest periods, even severe occlusion pressure (approximately 230 mmHg), which almost completely blocked blood flow, was well-tolerated by the participants. Five muscle-specific microRNAs were measured from the biopsy samples, which were taken 2 h after the acute training. ResultsDoppler data showed that the pattern of blood flow recovery changed significantly between the first and last BFR. microRNA-206 levels significantly decreased in the BFR leg compared to the control. The mRNA levels of RAC-β serine/threonine-protein kinase v22, nuclear respiratory factor 1, vascular endothelial growth factor, lupus Ku autoantigen protein p70 genes (p < 0.05), and paired box 7 (p < 0.01) increased in the BFR leg. The protein levels of paired box 7, nuclear respiratory factor 1, and peroxisome proliferator-activated receptor γ coactivator 1α did not differ between the BFR leg and the control leg. ConclusionBFR, during the rest periods of high-load resistance training, could lead to mRNA elevation of those proteins that regulate angiogenesis, mitochondrial biogenesis, and muscle hypertrophy and repair. However, BFR also can cause DNA damage, judging from the increase in mRNA levels of lupus Ku autoantigen protein p70.

Twelve weeks of resistance training does not influence peripheral levels of neurotrophic growth factors or homocysteine in healthy adults: a randomized-controlled trial.

There is growing evidence for a preventative effect of resistance training on cognitive decline through physiological mechanisms; yet, the effect of resistance training on resting growth factors and homocysteine levels is incompletely understood. This study aimed to investigate the effect of intense resistance training, for 12weeks, on changes in peripheral growth factors and homocysteine in late middle-aged adults. 45 healthy adults were enrolled into the single-site parallel groups' randomized-controlled trial conducted at the Department of Exercise Science, Strength and Conditioning Laboratory, Murdoch University. Participants were allocated to the following conditions: (1) high-load resistance training (n = 14), or (2) moderate-load resistance training (n = 15) twice per week for 12weeks; or (3) non-exercising control group (n = 16). Data were collected from September 2016 to December 2017. Fasted blood samples were collected at baseline and within 7 days of trial completion for the analysis of resting serum brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1, vascular endothelial growth factor, and plasma homocysteine levels. No differences in baseline to post-intervention change in serum growth factors or plasma homocysteine levels were observed between groups. A medium effect was calculated for BDNF change within the high-load condition alone (+ 12.9%, g = 0.54). High-load or moderate-load resistance training twice per week for 12weeks has no effect on peripheral growth factors or homocysteine in healthy late middle-aged adults. Australian New Zealand Clinical Trials Registry: ACTRN12616000690459.

Differential muscle hypertrophy and edema responses between high-load and low-load exercise with blood flow restriction.

We sought to determine whether early increases in cross-sectional area (CSA) of different muscles composing the quadriceps with low-load resistance training with blood flow restriction (LL-BFR) were mainly driven by muscle hypertrophy or by edema-induced swelling. We also compared these changes to those promoted by high-load resistance training (HL-RT). In a randomized within-subject design, fifteen healthy, untrained men were submitted to magnetic resonance imaging (MRI) for CSA and edema-induced muscle swelling assessment (fast spin echo inversion recovery, FSE-STIR). MRI was performed in LL-BFR and HL-RT at baseline (W0) and after 3weeks (W3), with a further measure after 6weeks (W6) for HL-RT. Participants were also assessed at these time points for indirect muscle damage markers (range of motion, ROM; muscle soreness, SOR). CSA significantly increased for all the quadriceps muscles, for both LL-BFR and HL-RT at W3 (all P<.05) compared to W0. However, FSE-STIR was elevated at W3 for all the quadriceps muscles only for HL-RT (all P<.0001), not LL-BFR (all P>.05). Significant increases and decreases were shown in SOR and ROM, respectively, for HL-RT in W3 compared to W0 (both P<.05), while these changes were mitigated at W6 compared to W0 (both P>.05). No significant changes in SOR or ROM were demonstrated for LL-BFR across the study. Early increases in CSA with LL-BFR seem to occur without the presence of muscle edema, whereas initial gains obtained by HL-RT were influenced by muscle edema, in addition to muscle hypertrophy.

Combined exercise and visual gaze training improves stepping accuracy in people with diabetic peripheral neuropathy

IntroductionPatients with diabetes and diabetic peripheral neuropathy (DPN) place their feet with less accuracy whilst walking, which may contribute to the increased falls-risk. This study examines the effects of a multi-faceted intervention on stepping accuracy, in patients with diabetes and DPN. MethodsForty participants began the study, of which 29 completed both the pre and post-intervention tests, 8 patients with DPN, 11 patients with diabetes but no neuropathy (D) and 10 healthy controls (C). Accuracy of stepping was measured pre- and post-intervention as participants walked along an irregularly arranged stepping walkway. Participants attended a one-hour session, once a week, for sixteen weeks, involving high-load resistance exercise and visual-motor training. ResultsPatients who took part in the intervention improved stepping accuracy (DPN: +45%; D: +36%) (p < 0.05). The diabetic non-intervention (D-NI) group did not display any significant differences in stepping accuracy pre- to post- the intervention period (−7%). DiscussionThe improved stepping accuracy observed in patients with diabetes and DPN as a result of this novel intervention, may contribute towards reducing falls-risk. This multi-faceted intervention presents promise for improving the general mobility and safety of patients during walking and could be considered for inclusion as part of clinical treatment programmes.

Low-Load vs. High-Load Resistance Training to Failure on One Repetition Maximum Strength and Body Composition in Untrained Women.

Dinyer, TK, Byrd, MT, Garver, MJ, Rickard, AJ, Miller, WM, Burns, S, Clasey, JL, and Bergstrom, HC. Low-load vs. high-load resistance training to failure on one repetition maximum strength and body composition in untrained women. J Strength Cond Res 33(7): 1737-1744, 2019-This study examined the effects of resistance training (RT) to failure at low and high loads on one repetition maximum (1RM) strength and body composition (bone- and fat-free mass [BFFM] and percent body fat [%BF]) in untrained women. Twenty-three untrained women (age: 21.2 ± 2.2 years; height: 167.1 ± 5.7 cm; body mass: 62.3 ± 16.2 kg) completed a 12-week RT to failure intervention at a low (30% 1RM) (n = 11) or high (80% 1RM) (n = 12) load. On weeks 1, 5, and 12, subjects completed 1RM testing for 4 different exercises (leg extension [LE], seated military press [SMP], leg curl [LC], and lat pull down [LPD]) and a dual-energy x-ray absorptiometry scan to assess body composition. During weeks 2-4 and 6-7, the subjects completed 2 sets to failure for each exercise. During weeks 8-11, the subjects completed 3 sets to failure for each exercise. The 1RM strength increased from week 1 to week 5 (LE: 18 ± 16%; SMP: 9 ± 11%; LC: 12 ± 22%; LPD: 13 ± 9%), week 1 to week 12 (LE: 32 ± 24%; SMP: 17 ± 14%; LC: 23 ± 26%; LPD: 25 ± 13%), and week 5 to week 12 (LE: 11 ± 9%; SMP: 7 ± 9%; LC: 10 ± 7%; LPD: 11 ± 11%) in each exercise, with no significant differences between groups. There were no significant changes in BFFM (p = 0.241) or %BF (p = 0.740) for either group. Resistance training to failure at 30% 1RM and 80% 1RM resulted in similar increases in 1RM strength, but no change in BFFM or %BF. Untrained women can increase 1RM strength during RT at low and high loads, if repetitions are taken to failure.

Lower and Higher Load Resistance Exercise Protocols: Acute Muscle Activation and Skeletal Muscle Hypertrophy

Lower and Higher Load Resistance Exercise Protocols: Acute Muscle Activation and Skeletal Muscle Hypertrophy

Probing swift heavy ion irradiation damage in Nd-doped zirconolite

Synroc minerals have been studied since decades for immobilization of high-level radioactive wastes released from nuclear weapons and nuclear reactors. Among them, the zirconolite, due to its high radiation and aqueous resistance and high waste loading, is considered as a potential candidate for containment purposes. Though irradiation damage effects of swift heavy ions in the material remain a major concern of study, a single phase Nd-doped zirconolite samples prepared through conventional solid-state reaction were irradiated with 120 MeV Au+ ions to study radiation damage effects. Irradiation-induced effects were investigated using ex-situ XRD and micro-Raman spectroscopic techniques. Zirconolite has been observed to undergo amorphization which is confirmed through disappearance of characteristic x-ray diffraction peaks and appearance of broad diffuse scattering bands. Amorphization trend with fluence appeared linear at lower fluences followed by saturation at higher fluences inferring therewith the formation of ion tracks. The ion fluence dependent Raman examination was also found to be in line with the XRD observations. However, the presence of Raman modes, characteristic of zirconolite in the 100–1000 cm−1 region, showed intact behavior of the local structure. To sum up, the 120 MeV heavy Au+ ions developed columnar defects, vacancies and induced micro-strains that lead to the bonds distortion and eventually amorphization of the zirconolite though retaining local ordering.

Inductive excitation of a serial RLC-circuit with rectangular voltage pulses. Calculated relations

Problem. The “voltage resonance” conditions in the well-known theories and applications, as a rule, are formulated only for a sinusoidal signal, at a certain frequency and in a steady state. Inductive excitation of a sequential active-reactive circuit with anharmonic signals from a practical point of view is of greater interest. Goal. The purpose of this work is to obtain design ratios for the characteristics of inductive excitation of voltage resonance in a system of two inductively coupled sequential active-reactive circuits by anharmonic signals, the spectrum of which, along with the fundamental frequency of oscillations, contains so-called higher harmonics with frequencies multiple to the main type of oscillations. Methodology. With the help of limiting transitions to the corresponding, the reliability of the found basic analytical dependences for the excited currents and voltages is shown. The obtained calculated relations are based on rigorous mathematical approach using the apparatus of the theory of electrical circuits. Results. The amplitude-time form of the excited current is found by solving the transient problem. The dependence obtained allows us to analyze the flowing processes, determine the effect of circuit electrical parameters and establish the contribution of higher harmonics to the formation of the output signal, as well as calculate specific indicators of the effectiveness and efficiency of the system under consideration under anharmonic excitation. Originality. The scientific novelty consists in obtaining the calculated amplitude-time dependence for the current in the secondary circuit with inductive excitation of the voltage resonance in a system of two inductively connected successive active-reactive circuits by anharmonic signals, whose spectrum, together with the fundamental frequency of oscillations, contains the so-called highest harmonics with frequencies multiples of the main type of vibrations. Practical value. The results of the analysis are necessary for the design of electrical devices with resonant components. For example, to supply high-resistance loads with increased voltage, in induction heating devices, etc.Key words: Tesla transformer; inductively coupled circuits; Q-factor; transformation ratio; voltage amplifier.

Electromechanical dynamics of Z-shaped mechatronic synchronized switch harvesting on inductor (SSHI) harvester

The electromechanical properties of a Z-shaped mechatronic synchronized switch harvesting on inductor (SSHI) harvester that can produce high output powers from a compact configuration were investigated numerically and experimentally. The second vibrational mode shows a several-fold increase in output power over the first one because the vertical movement of the mass effectively applies high stress to the piezoelectric material. We employed a two-way coupled simulation technique to investigate the performance of the mechatronic SSHI harvester numerically. Overall, the simulation results match the experimental results well. The output power for the mechatronic SSHI harvester shows a 1.8-fold increase over that of a standard AC–DC circuit experimentally. The numerical analysis revealed that a switch-skipping phenomena cause a reduction of the output power from the mechatronic SSHI harvester for higher resistive loads. The piezoelectric coupling force, which increases at these high resistive loads, suppressed the harvester’s displacement and this caused the switch-skipping behavior.

High Pressure Blood Flow Restriction Is Necessary For Peripheral Vascular Adaptations With Very Low Loads

Low-load resistance exercise combined with blood flow restriction (BFR) has the ability to increase muscle mass following periods of training. Peripheral vascular adaptations to this type of exercise have been examined at loads commonly used [30% of one-repetition maximum (1RM)]. Vascular adaptations occur through flow-induced sheer stress, mechanical compression due to muscular contraction, and circumferential strain induced by pressure waves. Loads lower than 30% 1RM (i.e. 15% 1RM) may not induce enough mechanical stress to stimulate adaptation, and higher BFR pressures may be required. PURPOSE: To examine the peripheral vascular response to eight weeks of training using very low loads combined with differing BFR pressures in the upper body. METHODS: Forearm blood flow (FBF), vascular conductance (FVC), and venous compliance (FCV) were measured using strain-gauge plethysmography before and following eight weeks of 2x/week resistance training of the elbow flexors using 15% 1RM combined with either no BFR [15/0], 40% of arterial occlusion pressure (AOP) [15/40], or 80% of AOP [15/80], and were compared to high load resistance exercise at 70% 1RM [70/0] in 20 men and 20 women. Results reported as Mean (SE). RESULTS: FBF exhibited a condition x time interaction (P=.043). The training response to 15/80 and 70/0 were greater (+0.520 (0.22), +0.616 (0.22) ml·min-1·100ml-1, respectively) than 15/0 and 15/40 (+0.077 (0.22), -0.137 (0.21) ml·min-1·100ml-1, respectively). A similar interaction existed for FVC (P=.032), with 15/80 and 70/0 showing a greater response (+8.286 (2.66), +8.595 (2.6) ml·mmHg-1, respectively) than did 15/0 and 15/40 (+1.813 (2.66), -0.413 (2.6) ml·mmHg-1, respectively). FCV displayed only a main effect of time (P=.044), increasing 0.003 (0.002) %·mmHg-1. CONCLUSIONS: At very low loads (15% 1RM), FBF and FVC were increased only in the high pressure group in a manner not different from high load, lending support to the conclusion that circumferential strain on arterioles can lead to vascular adaptation. The lack of difference in the FCV response implies that even very low loads affect compliance. Future research should examine the possibility of capillarization occurring following repeated exposure to high pressure BFR.

Six Weeks of Low-Load Blood Flow Restricted and High-Load Resistance Exercise Training Produce Similar Increases in Cumulative Myofibrillar Protein Synthesis and Ribosomal Biogenesis in Healthy Males.

Purpose: High-load resistance exercise contributes to maintenance of muscle mass, muscle protein quality, and contractile function by stimulation of muscle protein synthesis (MPS), hypertrophy, and strength gains. However, high loading may not be feasible in several clinical populations. Low-load blood flow restricted resistance exercise (BFRRE) may provide an alternative approach. However, the long-term protein synthetic response to BFRRE is unknown and the myocellular adaptations to prolonged BFRRE are not well described.Methods: To investigate this, 34 healthy young subjects were randomized to 6 weeks of low-load BFRRE, HLRE, or non-exercise control (CON). Deuterium oxide (D2O) was orally administered throughout the intervention period. Muscle biopsies from m. vastus lateralis were collected before and after the 6-week intervention period to assess long-term myofibrillar MPS and RNA synthesis as well as muscle fiber-type-specific cross-sectional area (CSA), satellite cell content, and myonuclei content. Muscle biopsies were also collected in the immediate hours following single-bout exercise to assess signaling for muscle protein degradation. Isometric and dynamic quadriceps muscle strength was evaluated before and after the intervention.Results: Myofibrillar MPS was higher in BFRRE (1.34%/day, p < 0.01) and HLRE (1.12%/day, p < 0.05) compared to CON (0.96%/day) with no significant differences between exercise groups. Muscle RNA synthesis was higher in BFRRE (0.65%/day, p < 0.001) and HLRE (0.55%/day, p < 0.01) compared to CON (0.38%/day) and both training groups increased RNA content, indicating ribosomal biogenesis in response to exercise. BFRRE and HLRE both activated muscle degradation signaling. Muscle strength increased 6–10% in BFRRE (p < 0.05) and 13–23% in HLRE (p < 0.01). Dynamic muscle strength increased to a greater extent in HLRE (p < 0.05). No changes in type I and type II muscle fiber-type-specific CSA, satellite cell content, or myonuclei content were observed.Conclusions: These results demonstrate that BFRRE increases long-term muscle protein turnover, ribosomal biogenesis, and muscle strength to a similar degree as HLRE. These findings emphasize the potential application of low-load BFRRE to stimulate muscle protein turnover and increase muscle function in clinical populations where high loading is untenable.

Muscle damage responses to resistance exercise performed with high-load versus low-load associated with partial blood flow restriction in young women

The aim of this study was to compare if an acute exercise session of high-load resistance training (HL-RT, e.g. 70% of 1 repetition-maximum, 1 RM) induces a higher magnitude of muscle damage compared with a RT protocol with low-loads (e.g. 20% 1 RM) associated with partial blood flow restriction (LL-BFR), and investigate the recovery in the days after the protocols. We used an unilateral crossover research design in which 10 young women (22(2) y; 162(5) cm; 66(11) kg) performed HL-RT and LL-BFR in a randomized, counterbalanced manner with a minimum interval of 2 weeks between protocols. Indirect muscle damage markers were evaluated before and once a day for 4 days into recovery. Main results showed decreases of 8–12% at 24–48 h in maximal voluntary isometric and concentric contraction torques (P < 0.03), and changes in muscle architecture markers (P < 0.03) for HL-RT and LL-BFR, with no differences between protocols (P > 0.05). Moreover, delayed onset muscle soreness increased only after LL-BFR (P < 0.001). We conclude that an acute bout of low volume HL-RT or LL-BFR to failure resulted in edema-induced muscle swelling, but do not induce major or long-lasting decrements in muscle function and the level of soreness promoted from LL-BFR was mild.