Comparing the acute responses between a manual and automated blood flow restriction system.

The purpose of this study was to compare acute responses between manual and automated blood flow restriction (BFR) systems. Methods: A total of 33 individuals completed this study. On visit 1, arterial occlusion pressure (AOP, mm Hg), cardiovascular responses, and discomfort (RPE-D) were measured with each BFR system at rest. On visit 2, unilateral bicep curls were completed [30% one-repetition maximum; 50% AOP] with one system per arm. Muscle thickness (MT, cm) and maximal force (N) were assessed before (pre), immediately (post-0), 5 min (post-5), and 10 min (post-10) post-exercise. Ratings of perceived exertion (RPE-E) and ratings of perceived discomfort (RPE-D) were assessed throughout the exercise. AOP and repetitions were compared with Bayesian paired t-tests. Other outcomes were compared with Bayesian RMANOVAs. BF10 represents the likelihood of the best model vs. the null. The results are presented as mean ± SD. Results: Supine cardiovascular responses and RPE-D were similar for manual and automated (all BF10 ≤ 0.2). Supine AOP for manual (157 ± 20) was higher than that of automated (142 ± 17; BF10 = 44496.0), but similar while standing (manual: 141 ± 17; automated: 141 ± 22; BF10 = 0.2). MT (time, BF10 = 6.047e + 40) increased from Pre (3.9 ± 0.7) to Post-0 (4.4 ± 0.8; BF10 = 2.969e + 28), with Post-0 higher than Post-5 (4.3 ± 0.8) and Post-10 (4.3 ± 0.8; both BF10 ≥ 275.2). Force (time, BF10 = 1.246e + 29) decreased from Pre (234.5 ± 79.2) to Post-0 (149.8 ± 52.3; BF10 = 2.720e + 22) and increased from Post-0 to Post-5 (193.3 ± 72.7; BF10 = 1.744e + 13), with Post-5 to Post-10 (194.0 ± 70.6; BF10 = 0.2) being similar. RPE-E increased over sets. RPE-D was lower for manual than automated. Repetitions per set were higher for manual (Set 1: 37 ± 18; Set 4: 9 ± 5) than automated (Set 1: 30 ± 7; Set 4: 7 ± 3; all BF10 ≥ 9.7). Conclusion: Under the same relative pressure, responses are mostly similar between BFR systems, although a manual system led to lower exercise discomfort and more repetitions.

Caffeine Abstinence in Habituated Users: Cardiovascular Responses to Exercise With Blood Flow Restriction.

CONTEXT: Blood flow restriction resistance exercise studies often require caffeine abstinence to avoid cardiovascular effects that could change the blood flow restriction stimulus. However, effects may be attenuated for habituated users. OBJECTIVE: To compare cardiovascular responses to blood flow restriction resistance exercise when habituated users consume or abstain from caffeine. DESIGN: Thirty participants completed a 3-visit within-subject study beginning with familiarization and caffeine intake questionnaire. METHODS: Visits 2 and 3 consisted of blood flow restriction resistance exercise (3 sets bicep curls to failure, 30% 1-repetition max, 40% arterial occlusion pressure [AOP]), following participants' normal caffeine consumption (CAFF) or abstaining (ABS). AOP, systolic (SBP) and diastolic (DBP) blood pressure, and heart rate were measured preexercise and postexercise. Prevalues and preexercise to postexercise change scores for SBP, DBP, AOP (all millimeters of mercury), heart rate (in beats per minute), and repetitions were compared between conditions. Results are represented as mean (SD). RESULTS: Preexercise AOP was similar for CAFF (137.8 [14.4]) and ABS (137.1 [14.9], BF10 = 0.2), although pre-SBP was higher for CAFF (115.4 [9.8]) than ABS (112.3 [9.4], BF10 = 1.9). Pre-DBP was similar between conditions. The exercise-induced change in AOP was greater for CAFF (18.4 [11.2]) than ABS (13.2 [14.9]), though evidence was anecdotal (BF10 = 0.7). Exercise-induced changes in SBP, DBP, and heart rate were similar between conditions (all BF10 ≤ 0.40). More repetitions were completed for CAFF (63 [26]) than ABS (57 [17], BF10 = 2.1). CONCLUSIONS: The findings of this study suggest that for habituated users, maintaining daily caffeine habits will not have substantial effects on common cardiovascular variables relevant to blood flow restriction.

Post-occlusive reactive hyperemia in habituated caffeine users: Effects of abstaining versus consuming typical doses.

BACKGROUND: Post-occlusive reactive hyperemia (PORH) typically requires caffeine abstinence. For habitual users, it is unknown if abstinence affects PORH. OBJECTIVE: Compare PORH after habitual users consume or abstain from caffeine. METHODS: On separate visits (within-subject), PORH was measured in 30 participants without abstinence from typical caffeine doses (CAFF) and with abstinence (ABS). Measurements included baseline and peak hyperemic velocity, tissue saturation index slopes during ischemia (Slope 1) and following cuff deflation (Slope 2), resting arterial occlusion pressure (AOP), heart rate (HR), systolic (SBP), and diastolic (DBP) blood pressure. All variables were compared using Bayesian paired t-tests. BF10 = likelihood of alternative vs null. Results are mean±SD. RESULTS: Comparing baseline velocity (cm/s) between CAFF (9.3±4.8) and ABS (7.5±4.9) yielded anecdotal evidence (BF10 = 1.0). Peak hyperemic velocity (cm/s) was similar (CAFF = 77.3±16.7; ABS = 77.6±19.0, BF10 = 0.20). For slopes (TSI% /s), CAFF Slope 1 = -0.11±0.04 and Slope 2 = 1.9±0.46 were similar (both BF10≤0.20) to ABS Slope 1 = -0.12±0.03 and Slope 2 = 1.8±0.42. SBP and DBP (mmHg) were both similar (CAFF SBP = 116.0±9.8, DBP = 69.6±5.8; ABS SBP = 115.5±10.7, DBP = 69.5±5.4; both BF10≤0.22). Comparing AOP (mmHg) (CAFF = 146.6±15.0; ABS = 143.0±16.4) yielded anecdotal evidence (BF10 = 0.46). HR (bpm) was similar (CAFF = 66.5±12.3; ABS = 66.9±13.0; BF10 = 0.20). CONCLUSIONS: In habitual users, consuming or abstaining from typical caffeine doses does not appear to affect post-occlusive reactive hyperemia.

Affective and Perceptual Responses During an 8-Week Resistance Training to Failure Intervention at Low vs. High Loads in Untrained Women.

ABSTRACT: Anderson, AlOK, Voskuil, CC, Byrd, MT, Garver, MJ, Rickard, AJ, Miller, WM, Bergstrom, HC, and Dinyer McNeely, TK. Affective and perceptual responses during an 8-week resistance training to failure intervention at low vs. high loads in untrained women. J Strength Cond Res 37(3): 546-554, 2023-This study examined the effects of resistance training (RT) to failure on the perceptual and affective responses, intent-to-continue RT to failure in a self-initiated session, and affect-intent relationship. Twenty-three untrained women (mean ± SD : age 21.2 ± 2.2 years; height 167 ± 5.7 cm; body mass, 62.3 ± 16.2 kg) completed an 8-week, full-body RT to failure intervention at a low (30% 1RM; n = 11) or high (80% 1RM; n = 12) load. The Borg's rating of perceived exertion (RPE) scale was used to assess the acute (aRPE) and session (sRPE) RPE immediately after repetition failure and each training session, respectively. Immediately, 15-minute, and 60-minute postsession affective responses were assessed using the feeling scale (FS; -5 to +5), and intent to continue to RT was assessed on a scale of 0-100% intention. During week 4 (W4) and week 8 (W8), aRPE (W4: 18 ± 2, W8: 18 ± 2; p ≤ 0.032) and sRPE (W4: 17 ± 2, W8: 18 ± 1; p ≤ 0.018) were greater than that during week 1 (W1; aRPE: 17 ± 2; sRPE: 16 ± 2). The FS responses increased from immediately to 60-minute postsession during W4 ( p ≤ 0.019) and W8 ( p ≤ 0.049). The correlation between affect and intent-to-continue RT increased from W1 ( r = 0.416) to W8 ( r = 0.777). Regardless of load, untrained women reported similar perceptual, affective, and intention responses. These variables should be considered to improve RT program adoption and adherence in women.

Effect of repeated eccentric exercise on muscle damage markers and motor unit control strategies in arm and hand muscle.

To examine the contralateral repeated bout effect (CL-RBE) on muscle damage markers and motor unit (MU) control strategies, seventeen healthy adults performed two bouts of 60 eccentric contractions with elbow flexor (EF group; n â€‹= â€‹9) or index finger abductor (IA group; n â€‹= â€‹8) muscles, separated by 1 week. All participants randomly performed eccentric exercise on either the right or left arm or hand muscles, and muscle damage markers and submaximal trapezoid contraction tests were conducted pre, post, 1- and 2-day post eccentric protocol. One week after the first bout, the same exercise protocol and measurements were performed on the contralateral muscles. Surface electromyographic (EMG) signals were collected from biceps brachii (BB) or first dorsal interosseous (FDI) during maximal and submaximal tests. The linear regression analyses were used to examine MU recruitment threshold versus mean firing rate and recruitment threshold versus derecruitment threshold relationships. EMG amplitude from BB (bout 1 vs. bout 2 â€‹= â€‹65.71% â€‹± â€‹22.92% vs. 43.05% â€‹± â€‹18.97%, p â€‹= â€‹0.015, d â€‹= â€‹1.077) and the y-intercept (group merged) from the MU recruitment threshold versus derecruitment threshold relationship (bout 1 vs. bout 2 â€‹= â€‹-7.10 â€‹± â€‹14.20 vs. 0.73 â€‹± â€‹16.24, p â€‹= â€‹0.029, d â€‹= â€‹0.513) at 50% MVIC were significantly different between two bouts. However, other muscle damage markers did not show any CL-RBE in both muscle groups. Therefore, despite changes in muscle excitation and MU firing behavior, our results do not support the existence of CL-RBE on BB and FDI muscles.

A comparison of variability between absolute and relative blood flow restriction pressures.

INTRODUCTION: Recommendations are that blood flow restriction (BFR) be applied relative to arterial occlusion pressure (AOP) to provide a similar stimulus. PURPOSE: Compare variability of the change in blood flow, shear rate and discomfort between recommended relative pressures and an absolute pressure. METHODS: During one visit, brachial arterial blood flow was measured in 91 participants using pulse-wave Doppler ultrasonography. After 5-min seated rest, AOP was measured. Following another 5-min rest, blood flow and discomfort were assessed twice before cuff inflation as controls (C1 and C2), then again with a cuff inflated to each BFR pressure (all measures separated by 1-min). Change scores from C1 to all subsequent measures were calculated (i.e., C2-C1; 40% AOP-C1; 80% AOP-C1; 100 mmHg-C1). Variability of the changes were compared via pairwise modified Pitman-Morgan tests (α = 0.008). RESULTS: Variance (95% CI) of the change for blood flow (ml/min), shear rate (1/s), and discomfort (AU) had similar trends. C2-C1 differed from all conditions (all p < 0.001), 40% AOP-C1 differed from 80% AOP-C1 and 100 mmHg-C1 (all p < 0.001), which did not differ (both p ≥ 0.117). Blood flow: C2-C1 = 469.79 (357.90, 644.07), 40% AOP-C1 = 1263.18 (962.34, 1731.80), 80% AOP-C1 = 1752.90 (1335.42, 2403.18), 100 mmHg-C1 = 1603.18 (1221.36, 2197.92); shear rate: C2-C1 = 6248.24 (4760.10, 8566.15), 40% AOP-C1 = 14 625.30 (11 142.06, 20 050.95), 80% AOP-C1 = 22 064.02 (16 809.13, 30 249.27), 100 mmHg-C1 = 20 778.76 (15 829.98, 28 487.21); discomfort: C2-C1 = 0.07 (0.05, 0.08), 40% AOP-C1 = 2.03 (1.55, 2.78), 80% AOP-C1 = 4.26 (3.25, 5.84), 100 mmHg-C1 = 4.50 (3.43, 6.17). CONCLUSION: Contrary to previous suggestions, applying relative pressures does not necessarily guarantee a similar stimulus. It seems that higher pressures produce more variable changes even if the external pressure applied is made relative to each individual.

Effect of Arm Eccentric Exercise on Muscle Damage of the Knee Flexors After High-Intensity Eccentric Exercise.

Repeated bout effect (RBE) describes a phenomenon that an initial unaccustomed eccentric exercise (ECC) bout can confer a protective effect against muscle damage from the subsequent same exercise. This protection has been observed in the same muscle, as well as the contralateral homologous (CL-RBE) muscle. But it is unknown whether the RBE is evident for non-local unrelated heterogonous muscles. The purpose of this study was to examine whether an initial elbow flexion (EF) muscle-damaging ECC could confer RBE against muscle damage from the subsequent ECC performed in the remote lower limb knee flexor (KF) muscle group. Twenty-seven young individuals were randomly assigned into the experimental (EXP: n = 15) and the control (CON: n = 12) groups. All participants performed a baseline unilateral KF ECC (six sets of 10 repetitions) on a randomly chosen leg. After a washout period (4 weeks), the EXP group performed 60 high-intensity unilateral EF ECC on a randomly chosen arm, followed by the same intensity exercise using the contralateral KF muscle group 2 weeks later. The CON group performed the same contralateral KF ECC, but with no prior EF ECC bout. Changes in the KF muscle damage indirect markers (muscle soreness, range of motion, and maximal isometric strength) after the ECC were compared between the baseline and second bouts for both groups with mixed factorial three-way (group × bout × time) ANOVA. Additionally, index of protection for each damage marker was calculated at 1 and 2 days after the ECC and compared between groups with independent t-tests. For both groups, the magnitude of the changes in the damage markers between the baseline and the second ECC bouts were not significantly different (all values of p > 0.05). As for the index of protection, relative to the CON, the EXP showed an exacerbating damaging effect on the KF isometric strength following the second ECC bout, particularly at the 1-day post-exercise time point (index of protection: EXP vs. CON mean ± SD = -29.36 ± 29.21 vs. 55.28 ± 23.83%, p = 0.040). Therefore, our results do not support the existence of non-local RBE.

Downhill running impairs peripheral but not central neuromuscular indices in elbow flexor muscles.

The purpose of this study was to examine the effects of a 1-h downhill running exercise on the elbow flexor muscles' neuromuscular functions. Seventeen adults (Control [CON]: n = 9; Experimental [EXP]: n = 8) completed this study. The CON rested for 30 min while the EXP performed the downhill running. Before, 10 min, 24 h, and 48 h after the interventions, dependent variables (knee extensor muscle soreness, elbow flexion and knee extension isometric strength, elbow flexion resting twitch and voluntary activation [VA], and the biceps surface electromyography [EMG] amplitude) were measured. Knee extensor muscle soreness was significantly greater in the EXP than the CON group following the intervention throughout the entire 48 h. This was accompanied by the greater decline in the knee extension strength in the EXP than the CON (mean ±â€¯SD: -6.9 ±â€¯3.4% vs. 1.0 ±â€¯3.2%, p = 0.044). The elbow flexion strength, VA, and EMG amplitude were not affected by the exercise. However, the decline of the elbow flexion resting twitch was greater in the EXP than the CON (-19.6 ±â€¯6.3% vs. 8.7 ±â€¯5.9%, p = 0.003). Therefore, the downhill running impaired the remote elbow flexor muscles at a peripheral level.

The Effects of a Preconditioning Rolling Session on Subsequent Eccentric Exercise-Induced Muscle Damage.

West, JT, Miller, WM, Jeon, S, and Ye, X. The effects of a preconditioning rolling session on subsequent eccentric exercise-induced muscle damage. J Strength Cond Res 34(8): 2112-2119, 2020-The aim of this study was to examine the effects of a preexercise unilateral quadriceps muscle rolling intervention on subsequent ipsilateral (IPSI) or contralateral (CTRA) knee extension eccentric exercise-induced muscle damage. Twenty-seven healthy volunteers (14 men) underwent an eccentric exercise protocol (6 sets of 10 repetitions with 75% of the maximal isometric strength) with a single-leg knee extension machine. Before the eccentric exercise, the subjects were randomly assigned to either (a) IPSI group: rolling the ipsilateral knee extensor muscles, (b) CTRA: rolling the contralateral muscles, or (c) Control: sitting for 6 minutes (same duration as the rolling intervention protocol) relaxed. The muscle soreness, passive knee extension range of motion, and knee extension isometric strength were measured before, immediately, 24 hours, and 48 hours after exercise. The magnitudes of the range of motion decrement were attenuated in both the IPSI (p = 0.031) and CTRA (p = 0.014) groups 24 hours after the eccentric exercise, when compared with the control. Isometric strength (p = 0.783) and muscle soreness (p = 0.586) responses were not significantly different among the 3 groups (time points and sexes merged). Additionally, women displayed an overall faster recovery than men in isometric strength (p = 0.001) and muscle soreness (p = 0.024), evidenced by the measurements at 48 hours after exercise. Our study suggests that unilateral quadriceps rolling intervention before high-intensity muscle-damaging exercise has a beneficial effect on maintaining range of motion in both the ipsilateral and contralateral muscles.

Knowledge, attitudes, intentions, and behavior related to green infrastructure for flood management: A systematic literature review.

Green infrastructure (GI), which mimics natural hydrological systems, is a promising solution for flood management at the intersection of urban built infrastructure and natural systems. However, it has not yet achieved widespread uptake, due in part to insufficient understanding of human dimensions of the broader socio-ecological-technical system. We therefore conducted a multidisciplinary systematic literature review to synthesize research on people's existing knowledge about flood risk and GI, and how that shapes their attitudes and motivation to adopt new solutions. We systematically screened 21,207 studies on GI for flood management; 85 met our inclusion criteria. We qualitatively analyzed these studies to extract results on knowledge, attitudes, intentions, and behavior relating to GI for flood management. Overall, knowledge of GI was low across the 44 studies in which it was evaluated. Seventy studies assessed attitudes about GI, including the functional, aesthetic, health and safety, recreational, conservation, financial, and cultural value of GI, albeit their measurement was inconsistent. Willingness to implement or pay for GI varied considerably across 55 studies in which it was measured. Twenty studies measured and documented behavior relating to GI use, and these found low rates of adoption. Few studies systematically assessed the role of demographic, socio-economic, or geographic characteristics that could influence individuals' knowledge, attitudes, intentions or behavior, and thereby the success of GI programs. We recommend that researchers should more systematically capture data on human dimensions of GI (i.e. knowledge, attitudes, intentions, and behavior) across diverse settings to improve program design and uptake, especially among vulnerable populations. Greater attention to the social component of the socio-ecological-technical system will help ensure that GI programs are equitable, inclusive, and sustainable.

A Comparison of Motor Unit Control Strategies between Two Different Isometric Tasks.

BACKGROUND: This study examined the motor unit (MU) control strategies for non-fatiguing isometric elbow flexion tasks at 40% and 70% maximal voluntary isometric contraction. METHODS: Nineteen healthy individuals performed two submaximal tasks with similar torque levels: contracting against an immovable object (force task), and maintaining the elbow joint angle against an external load (position task). Surface electromyographic (EMG) signals were collected from the agonist and antagonist muscles. The signals from the agonist were decomposed into individual action potential trains. The linear regression analysis was used to examine the MU recruitment threshold (RT) versus mean firing rates (MFR), and RT versus derecruitment threshold (DT) relationships. RESULTS: Both agonist and antagonist muscles' EMG amplitudes did not differ between two tasks. The linear slopes of the MU RT versus MFR and RT versus DT relationships during the position task were more negative (p = 0.010) and more positive (p = 0.023), respectively, when compared to the force task. CONCLUSIONS: To produce a similar force output, the position task may rely less on the recruitment of relatively high-threshold MUs. Additionally, as the force output decreases, MUs tend to derecruit at a higher force level during the position task.

Effects of Maximal vs. Submaximal Isometric Fatiguing Exercise on Subsequent Submaximal Exercise Performance.

Miller, WM, Ye, X, and Jeon, S. Effects of maximal vs. submaximal isometric fatiguing exercise on subsequent submaximal exercise performance. J Strength Cond Res 34(7): 1875-1883, 2020-Exercise-induced muscle fatigue directly influences subsequent exercise performance. Thus, we examined task failure times for submaximal intermittent fatiguing isometric contractions performed after a bout of sustained maximal vs. submaximal isometric fatiguing contractions with the dominant elbow flexors. Twenty physically active individuals 8 men (mean ± SD = 21.4 ± 1.8 years; 80.9 ± 12.5 kg; 180 ± 6.4 cm) and 12 women (mean ± SD = 21.4 ± 2.7; 66.8 ± 15.6 kg; 165.7 ± 7.1 cm) participated in a 3-visit randomized cross-over study. Visit 1 included familiarization, and 2 and 3 were randomized for sustained maximal (until force was below 50% of the maximal force value) or submaximal conditions (50% of maximal force until task failure), followed by submaximal intermittent isometric contractions to task failure. Surface electromyography was recorded through the biceps brachii during all fatiguing contractions. Task failure time was significantly shorter for the maximal compared with submaximal condition, and no significant difference in sex or condition was found for the subsequent fatiguing condition. Electromyography amplitude significantly increased in the submaximal intermittent isometric contractions from prefatigue and first and final postfatigue with no condition or sex differences. Electromyography mean frequency significantly decreased from prefatigue and first and final postfatigue for both sexes, with no condition or sex differences. With both maximal and submaximal exercises inducing the same level of force deficit, our results suggested that both exercises might have imposed a similar burden on the neuromuscular system, thereby not providing differential effects on the subsequent submaximal exercise performance.

Sex work, discrimination, drug use and violence: a pattern for HIV risk among transgender sex workers compared to MSM sex workers and other MSM in Guatemala.

The risk of HIV infection is higher among transgender women and cisgender men who have sex with men (MSM) compared to the general population due in part to social and contextual factors. This study aimed to determine the prevalence and association of alcohol and drug abuse, discrimination and violence among transgender sex workers compared to cisgender male sex workers and cisgender men who had not received money for sex in Guatemala City. In 2010, transgender women and cisgender men who had had sex with men or transgender women were recruited into a cross-sectional behavioural survey. Among transgender women, 86% received money for sex in the past year. Transgender sex workers were more likely to use drugs and binge drink, three times as likely to be discriminated against and eight times as likely to be forced to have sex compared to non-sex worker men. Male sex workers were twice as likely to use illicit drugs or experience physical violence and six times as likely to experience forced sex compared to non-sex worker men. Transgender and male sex workers would benefit from harm reduction for substance use, violence prevention, response and strategies to mitigate discrimination.

Soil hydrology drives ecological niche differentiation in a native prairie microbiome.

While the impacts of soil moisture on soil microbiome diversity and composition are well characterized, the influence of hydrological regime has been overlooked. As precipitation patterns are altered by climate change, understanding the impact of soil hydrology on community structure and function is critical. In this work, water level was continuously monitored for over a year in a Midwestern prairie-wetland at 10 cm depth increments up to a depth of 120 cm in 10 locations. We analyzed microbiome composition and edaphic factors in soil cores collected from this unique spatially distributed, longitudinal data set. We demonstrate that the fraction of time that each sample was inundated explains more variability in diversity and composition across this site than other commonly assessed edaphic factors, such as soil pH or depth. Finally, we show that these compositional changes influence abundance of ammonia oxidizers. The observed patterns in community composition and diversity are fundamentally regulated by the interaction of water with a structured landscape, particularly an elevated sand ridge characterized by drier conditions and a lower-lying wetland with more clayey soils. Similar processes are generally expected to influence the biogeography of many terrestrial environments, as morphology, hydrology and soil properties generally co-vary.

Comparison of Myoelectric Activity During a Suspension-Based and Traditional Split Squat.

Miller, WM, Barnes, JT, Sofo, SS, and Wagganer, JD. Comparison of myoelectric activity during a suspension-based and traditional split squat. J Strength Cond Res 33(12): 3236-3241, 2019-Over several decades, traditional resistance training has incorporated body-mass suspension training (SPT), for example, Total-Body Resistance Exercise (TRX); however, very little research has been completed investigating the effects of lower body SPT. Therefore, the purpose of this study was to assess sex differences in myoelectric activity via electromyography while performing a stable (i.e., bench) traditional split squat (TSS) compared with suspension body-mass split squat (TRXSS). Nineteen recreationally active individuals (mean ± SD = men: n = 9; 21.4 ± 2.1 years; 177.2 ± 9.0 cm; 84.2 ± 8.8 kg; women: n = 10; 21.5 ± 1.6 years; 160.7 ± 8.5 cm; 59.1 ± 7.9 kg) participated in this investigation. Subjects performed 3 training sessions, 1 familiarization and 2 (one for each variation) split squat. The TRXSS was performed by placing the rear foot within the foot cradle of the strap, while the TSS required placement of the rear foot on a stable bench (40.64 cm). The TRXSS resulted in higher peak and average myoelectric activity overall, as well as greater gluteus maximus myoelectric activity. No gender or rectus femoris myoelectric activity differences were found. The increased myoelectric activity of the gluteus maximus during the TRXSS was most likely due to increased medial/lateral stabilization demands on the suspended leg. These findings provide insight into TRX as a useful exercise modality for recreationally active or rehabilitative purposes.

A systematic review of the human health and social well-being outcomes of green infrastructure for stormwater and flood management.

BACKGROUND: The increase in frequency and intensity of urban flooding is a global challenge. Flooding directly impacts residents of industrialized cities with aging combined sewer systems, as well as cities with less centralized infrastructure to manage stormwater, fecal sludge, and wastewater. Green infrastructure is growing in popularity as a sustainable strategy to mimic nature-based flood management. Although its technical performance has been extensively studied, little is known about the effects of green stormwater infrastructure on human health and social well-being. METHODS: We conducted a multidisciplinary systematic review of peer-reviewed and gray literature on the effects of green infrastructure for stormwater and flood management on individuals', households', and communities' a) physical health; b) mental health; c) economic well-being; and d) flood resilience and social acceptance of green infrastructure. We systematically searched databases such as PubMed, Web of Science, and Scopus; the first 300 results in Google Scholar; and websites of key organizations including the United States Environmental Protection Agency. Study quality and strength of evidence was assessed for included studies, and descriptive data were extracted for a narrative summary. RESULTS: Out of 21,213 initial results, only 18 studies reported health or social well-being outcomes. Seven of these studies used primary data, and none allowed for causal inference. No studies connected green infrastructure for stormwater and flood management to mental or physical health outcomes. Thirteen studies were identified on economic outcomes, largely reporting a positive association between green infrastructure and property values. Five studies assessed changes in perceptions about green infrastructure, but with mixed results. Nearly half of all included studies were from Portland, Oregon. CONCLUSIONS: This global systematic review highlights the minimal evidence on human health and social well-being relating to green infrastructure for stormwater and flood management. To enable scale-up of this type of infrastructure to reduce flooding and improve ecological and human well-being, widespread acceptance of green infrastructure will be essential. Policymakers and planners need evidence on the full range of benefits from different contexts to enable financing and implementation of instfrastructure options, especially in highly urbanized, flood-prone settings around the world. Therefore, experts in social science, public health, and program evaluation must be integrated into interdisciplinary green infrastructure research to better relate infrastructure design to tangible human outcomes.

Unilateral hamstring foam rolling does not impair strength but the rate of force development of the contralateral muscle.

BACKGROUND: Self-administered foam rolling (SAFR) is an effective massage technique often used in sport and rehabilitation settings to improve range of motion (ROM) without impairing the strength performance. However, the effects of unilateral SAFR on contralateral non-intervened muscle's rate of force development (RFD) are unknown. Therefore, the purpose of this investigation was to examine the acute effects of unilateral hamstrings SAFR on the contralateral limb flexibility, the isometric strength, and the RFD parameters. METHODS: Thirty-four subjects (21 women) completed two separate randomly sequenced experimental visits, during which the control (rested for 10 min) or ten, 30-second SAFR were performed with the dominant hamstring muscle group. Before (Pre) and after (Post) the interventions, the contralateral hip flexion passive ROM, the maximal explosive isometric strength of the contralateral knee flexors with the corresponding prime mover muscles' surface electromyographic (EMG) amplitude were measured. Separate two-way (time ×intervention) repeated measures analyses of variance (ANOVAs) were used to examine the potential changes of the dependent variables. RESULTS: The SAFR significantly improved the contralateral limb ROM (Pre vs. Post: 68.3 ± 21.0 vs. 73.2 ± 23.2 degrees, p < 0.001; d = 0.22). No change was found for the contralateral isometric strength or the maximal EMG amplitude. For the RFD parameters, the percent changes of the RFDs for the first 50, 100, and 200 ms of the maximal explosive isometric contraction were -31.2%, -16.8%, and -10.1%, respectively, following the unilateral SAFR, relative to the control condition. In addition, the decrement of the first 50-ms RFD reached statistical significance (p = 0.007; Cohen's d = 0.44). CONCLUSION: Ten sets of 30-second unilateral hamstring SAFR improved the ROM of the non-intervened contralateral limb, but decreased its ability to generate force, especially during the early phase (e.g., 50 ms) of the maximal explosive contraction.

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.

Sex comparisons of agonist and antagonist muscle electromyographic parameters during two different submaximal isometric fatiguing tasks.

To examine the task failure time of the force- and position-based submaximal elbow flexion fatiguing tasks for both sexes, twelve men and eight women visited the laboratory for two separate experimental occasions. During the experiment, they pulled against a rigid restraint for the force task and maintained a constant elbow joint angle to support an equivalent inertial load for the position task. For both fatiguing tasks (50% of the isometric strength at the elbow joint angle of 135 degree), the task failure time, along with the surface electromyographic (EMG) amplitude and mean frequency (MNF) were measured. The average failure time was longer for the force task than that for the position task (sexes combined: 39.6 ± 16.6 sec vs. 33.9 ± 14.9 sec, P = 0.033). In addition, men were overall less fatigable than women (tasks combined: 42.0 ± 14.7 sec vs. 28.7 ± 10.3 sec, P = 0.020). The multiple regression analyses showed that the task failure time in women was solely predicted by the rate of change of the triceps EMG MNF. Thus, more fatigability of women in this study was likely due to the quicker fatiguing rate of the antagonist triceps brachii muscle. Different from most previous studies that have used 90-degree elbow joint angle, the current 135-degree joint angle setup might have created a situation where greater muscle activity from the related muscles (e.g., the antagonist) were required for women than for men to stabilize the joint, thereby resulting in a shorter task failure time.

Sex comparisons of the bilateral deficit in proximal and distal upper body limb muscles.

Bilateral deficit (BLD) describes a phenomenon that the force produced during maximal simultaneous bilateral contraction is lower than the sum of those produced unilaterally. The aim of this study was to examine the potential sex-related differences in BLD in upper body proximal and distal limb muscles. Ten men and eight women performed single-joint maximal contractions with their elbow flexors and index finger abductors at separate laboratory visits, during which the maximal isometric voluntary contractions (MVICs) were performed unilaterally and bilaterally with a randomized order in the designated muscle group. Surface electromyographic (EMG) signals were recorded from the prime movers of the designated muscle groups (biceps brachii and first dorsal interosseous) during the maximal contractions. Both men and women demonstrated BLD in their elbow flexors (deficit: men = -11.0 ±â€¯6.3%; women = -10.2 ±â€¯5.0%). Accompanied by this force deficit was the reduced EMG amplitude from the dominant biceps brachii (collapsed across sex: p = 0.045). For the index finger abductors, only men (deficit = -13.7 ±â€¯6.1%), but not women showed BLD. Our results suggested that the BLD in the proximal muscle group is likely induced by the decreased maximal muscle activity from the dominant prime mover. The absence of BLD in women's index finger muscle is largely due to the inter-subject variability possibly related to the sex hormone flux and unique levels of interhemispheric inhibition.