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Future climate change predictions for tropical forests highlight increased frequency and intensity of extreme drought events. However, it remains unclear whether large and small trees have differential strategies to tolerate drought due to the different niches they occupy. The future of tropical forests is ultimately dependent on the capacity of small trees (<10 cm in diameter) to adjust their hydraulic system to tolerate drought. To address this question, we evaluated whether the drought tolerance of neotropical small trees can adjust to experimental water stress and was different from tall trees. We measured multiple drought resistance-related hydraulic traits across nine common neotropical genera at the world's longest-running tropical forest throughfall-exclusion experiment and compared their responses with surviving large canopy trees. Small understorey trees in both the control and the throughfall-exclusion treatment had lower minimum stomatal conductance and maximum hydraulic leaf-specific conductivity relative to large trees of the same genera, as well as a greater hydraulic safety margin (HSM), percentage loss of conductivity and embolism resistance, demonstrating that they occupy a distinct hydraulic niche. Surprisingly, in response to the drought treatment, small trees increased specific hydraulic conductivity by 56.3% and leaf:sapwood area ratio by 45.6%. The greater HSM of small understorey trees relative to large canopy trees likely enabled them to adjust other aspects of their hydraulic systems to increase hydraulic conductivity and take advantage of increases in light availability in the understorey resulting from the drought-induced mortality of canopy trees. Our results demonstrate that differences in hydraulic strategies between small understorey and large canopy trees drive hydraulic niche segregation. Small understorey trees can adjust their hydraulic systems in response to changes in water and light availability, indicating that natural regeneration of tropical forests following long-term drought may be possible., (© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

The aim of our study was to investigate the viability and validity of blood sampling from the upper lip mucosa in healthy dogs and cats for monitoring transoperative glycemia and compare the results with those obtained from samples taken from previously described blood sampling sites for determination of glycemia using a glucose meter. Blood glucose (BG) levels were determined in samples taken from the upper lip mucosa of 24 dogs and 31 cats undergoing neutering or spaying surgeries. These values were compared to those of samples obtained from other sites previously described for capillary blood glucose monitoring (marginal ear vein, carpal pad in dogs, metacarpal pad in cats) using a glucose meter. Additionally, BG from peripheral venous blood was determined using a glucose meter, and the gold standard enzymatic colorimetric assay. The clinical reliability of BG values taken from lip mucosa and from all the other BG values measured by the glucose meter was evaluated using the error grid analysis modified by Parkes et al (2000). The upper lip mucosa was an easily accessible site for the obtainment of appropriate blood samples, and glucose levels read in these samples correlated positively with glycemic values read in blood samples from all other sites in dogs and cats. All BG made using glucose meters taken from all sites were within the clinically acceptable range when compared with enzymatic colorimetric assay (gold standard), and were analytically accurate according to the error grid (zones A and B). All blood sampling sites described in this work can be used to assess transoperative glycemia. The upper lip mucosa is a viable blood sampling site for precise monitoring of transoperative glycemia in healthy dogs and cats and shows promise for alternative blood glucose monitoring., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The purpose of the present study was to examine the time course of passive range of motion (PROM), passive torque (PASTQ), and musculo-tendinous stiffness (MTS) responses during constant-angle (CA) and constant-torque (CT) stretching of the leg flexors. Eleven healthy men [mean ± standard deviation (SD): age = 21.5 ± 2.3 years] performed 16 30-s bouts of CA and CT stretching of the leg flexors. PROM, PASTQ , and MTS were measured during stretches 1, 2, 4, 8, and 16. For PROM and PASTQ , there were no differences between CA and CT stretching treatments (P > 0.05); however, there were stretch-related differences (P < 0.001). PROM increased following one 30-s bout of stretching (collapsed across CA and CT stretching) with additional increases up to 8 min of stretching. PASTQ decreased following one 30-s bout of stretching (collapsed across CA and CT stretching) and continued to decrease up to 4 min of stretching. In contrast, only the CT stretching treatment resulted in changes to MTS (P < 0.001). MTS decreased after one 30-s bout of CT stretching, with subsequent decreases in MTS up to 6 min of stretching. These results suggested that CT stretching may be more appropriate than a stretch held at a constant muscle length for decreasing MTS., (© 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Recent evidence has shown acute static stretching may decrease hamstring-to-quadriceps (H:Q) ratios. However, the effects of static stretching on the functional H:Q ratio, which uses eccentric hamstrings muscle actions, have not been investigated. This study examined the acute effects of hamstrings and quadriceps static stretching on leg extensor and flexor concentric peak torque (PT), leg flexor eccentric PT, and the conventional and functional H:Q ratios. Twenty-two women (mean ± SD age=20.6 ± 1.9 years; body mass=64.6 ± 9.1 kg; height=164.5 ± 6.4 cm) performed three maximal voluntary unilateral isokinetic leg extension, flexion, and eccentric hamstring muscle actions at the angular velocities of 60 and 180°/s before and after a bout of hamstrings, quadriceps, and combined hamstrings and quadriceps static stretching, and a control condition. Two-way repeated measures ANOVAs (time × condition) were used to analyze the leg extension, flexion, and eccentric PT as well as the conventional and functional H:Q ratios. Results indicated that when collapsed across velocity, hamstrings-only stretching decreased the conventional ratios (P<0.05). Quadriceps-only and hamstrings and quadriceps stretching decreased the functional ratios (P<0.05). These findings suggested that stretching may adversely affect the conventional and functional H:Q ratios., (© 2011 John Wiley & Sons A/S.)

The present study examined the viscoelastic creep responses in vivo during repeated constant-torque stretches in human skeletal muscle. Twelve healthy participants completed four consecutive 30-s constant-torque passive stretches of the right plantar flexor muscles. Position and surface electromyographic (EMG) amplitude values were quantified at every 5-s period and the percent change in position was quantified for each 5-s epoch relative to the total increase in ankle joint position for each stretch. In addition, the absolute changes in position were plotted on a logarithmic time scale and fit with a linear regression line to examine both the rate of increase (slope) and the overall increase in position over the entire stretch (y-intercept). The percent change and slope were similar (P>0.05) over all four stretches, with the majority of increases in position occurring within the initial 15-20 s of each stretch (84%). Absolute ankle joint position and the y-intercept increased (P<0.05) following both the first and second stretch but plateaued (P>0.05) after the third stretch. In addition, EMG amplitude values did not change (P>0.05) during or between each 30-s stretch. These data indicate that the amount and rate of viscoelastic creep were similar during practical durations of constant-torque stretching despite no change in ankle joint position following three 30-s stretches., (© 2011 John Wiley & Sons A/S.)

Passive stiffness measurements are often used as a clinical tool to examine a muscle's passive lengthening characteristics. The purpose of this study was to examine the relationship between passive stiffness and evoked twitch properties prior to and following normalization of passive stiffness to muscle cross-sectional area (CSA). Ten healthy volunteers (mean ± SD age = 23 ± 3 year) performed passive range of motion, evoked twitch, and muscle CSA assessments of the plantar flexor muscles. Passive stiffness was determined from the slope of the final 5° of the angle-torque curve. Peak twitch torque (PTT) and rate of torque development (RTD) were determined via transcutaneous electrical stimulation, and muscle CSA was assessed using a peripheral quantitative computed tomography scanner. Pearson product moment correlation coefficients (r) were used to assess the relationships between passive stiffness and PTT and RTD and normalized passive stiffness (passive stiffness ⋅ muscle CSA(-1)) and PTT and RTD. Significant positive relationships were observed between passive stiffness and PTT (P = 0.003, r = 0.828) and RTD (P = 0.003, r = 0.825). There were no significant relationships between normalized passive stiffness and PTT (P = 0.290, r = 0.372) or RTD (P = 0.353, r = 0.329) demonstrating that stiffness did not account for a significant portion of the variance in twitch properties. Passive stiffness was largely influenced by the amount of muscle tissue in this study. Future studies that examine muscle stiffness and its relationship with performance measures, among different populations, and following various interventions may consider normalizing stiffness measurements to muscle CSA.

The purpose of the present study was to examine the acute effects of passives stretching versus prolonged vibration on the active and passive properties of voluntary and evoked muscle actions of the plantar flexors. Eleven healthy men performed the isometric maximal voluntary contractions (MVCs) and passive range of motion (PROM) assessments before and after 20 min of passive stretching (PS), vibration (VIB), and control (CON) conditions. In addition, percent voluntary activation was calculated from superimposed and potentiated doublets during the MVCs. Voluntary peak torque (PT) decreased by 11% and 4%, while surface electromyographic (EMG) amplitude decreased by 8% and 16% for the PS and VIB, respectively, with no changes during the CON The electromechanical delay (EMD) decreased and PROM increased following the PS, but was unchanged during the VIB and CON conditions. Musculotendinous stiffness (MTS) decreased at all joint angles following the PS, but decreased only at the furthest joint angle following the VIB. There were no changes in peak twitch torque (PTT), M-wave amplitude, and EMG amplitude during the PROM assessments for all conditions. Both PS and VIB elicited similar decreases in muscle activation, which may be the same centrally-mediated mechanism (i.e., y loop impairment). Changes in the EMD were inversely proportional to the changes in MTS, which occurred only following PS. The present findings indicated that the stretching- and vibration-induced force deficits may have resulted in part from similar centrally-mediated neural deficits, while an elongation of the series elastic component may also have affected the stretching-induced force deficit.

Aim: The purpose of this study was to examine the effects of posterior thigh and leg stretching on leg flexion peak torque (PT), leg extension PT, the hamstrings-to-quadriceps (H:Q) ratio, and electromyographic (EMG) amplitude of the hamstrings and quadriceps in recreationally-active men., Methods: Fifteen men (mean age + or - SD = 22.0 + or - 4.4 years; body mass = 82.7 + or - 16.1 kg; height = 173.1 + or - 6.8 cm) performed three maximal voluntary concentric isokinetic leg extension and flexion muscle actions at three randomly ordered angular velocities (60, 180, and 300 degrees x s(-1)) before and after hamstring and calf static stretching. The stretching protocol consisted of 1 unassisted and 3 assisted static stretching exercises designed to stretch the posterior muscles of the thigh and leg. Four repetitions of each stretch were held for 30 s with 20-s rest between repetitions., Results: These findings indicated no significant (P>0.05) stretching-induced changes in leg flexion PT, leg extension PT, or EMG amplitude at 60, 180, or 300 degrees .s-1. However, the non-significant (P>0.05) 2-4% increases in leg extension PT combined with the non-significant (P>0.05) 1-2% decreases in leg flexion PT resulted in the significant (P < or = 0.05) 2-9% decreases in the H:Q ratio from pre- to post-stretching for all three velocities., Conclusions: These findings suggested that static stretching of the hamstrings and calf muscles may decrease the H:Q ratio. These results may be useful for athletic trainers, physical therapists, and other allied health professionals who may use the H:Q ratio as a clinical assessment.

The purpose of the present study was to examine the acute effects of hamstring and calf stretching on leg extension and flexion peak torque (PT) and the hamstrings-to-quadriceps (H : Q) ratio during maximal, concentric isokinetic muscle actions at 60, 180, and 300 degrees . s (-1) in women. Thirteen women (mean age +/- SD = 20.8 +/- 1.8 yrs; height = 163.0 +/- 5.7 cm; mass = 64.0 +/- 8.3 kg) performed 3 maximal concentric isokinetic leg extension and flexion muscle actions at 3 randomly ordered angular velocities (60, 180, and 300 degrees . s (-1)) before and after a bout of static stretching. The stretching protocol consisted of 1 unassisted and 3 assisted static stretching exercises designed to stretch the posterior muscles of the thigh and leg. Four repetitions of each stretch were held for 30 s with 20 s rest between repetitions. The results indicated that leg flexion PT decreased from pre- to post-stretching (34.9 +/- 3.5 and 32.4 +/- 3.2 Nm, respectively) collapsed across velocity. However, no other changes were observed from pre- to post-stretching for leg extension PT (78.5 +/- 5.9 and 77.8 +/- 5.5 Nm, respectively) and the H : Q ratio (0.47 +/- 0.04 and 0.44 +/- 0.03, respectively). Our findings suggested that despite the stretching-induced decreases in leg flexion PT, leg extension PT and the H : Q ratios were unaltered by the stretching.

Objectives: This study examined the effects of 14 days of creatine supplementation on the physical working capacity at fatigue threshold (PWCFT), maximal isometric grip strength (GRIP), sit-to-stand (STS), and body weight (BW) in elderly men and women., Design: Using a double blind cross-over design, fifteen men (n = 7) and women (n = 8) (age +/- SD = 74.5 +/- 6.4 yrs) were randomly assigned to either the creatine (CR) (20g.d-1 during week 1 decreasing to 10g.d-1 at week 2) or Placebo (PL) group. After a 4 to 6 week washout period, the subjects were assigned the other treatment. Before (pre) and after (post) the supplementation period, participants performed a discontinuous, cycle ergometry test to determine the PWCFT. In addition, subjects performed STS, GRIP, BW test prior to and post treatment., Setting: Southeastern part of the United States., Results: Significant increases in GRIP (6.7%) and PWCFT (15.6%) from pre- to post-supplementation were found for the CR (p < 0.05) treatment, but no change for the PL treatment was observed. However, no significant change (p superior 0.05) was noted for STS or BW for either treatment., Conclusion: These findings suggest that 14 days of CR supplementation may increase upper body grip strength and increase physical working capacity by delaying neuromuscular fatigue in the elderly men and women in this study. While more research is needed, CR supplementation may improve upper body grip strength and lower body muscle endurance which may be important for maintaining health and independent living in elderly men and women.

Background: Orthotopic liver transplantation is an established therapy for patients with end-stage liver disease. In the last years more attention has been given for the improvement of the quality of life after liver transplantation, and the return to important life pursuits, such as employment, are important goals of this type of therapy., Aim: To assess the work's return rate in liver transplant recipients and the reasons for inability after liver transplant., Patients and Methods: Forty-one adults (age > or = 18 years) who underwent liver transplantation at our institution, between September 1991 and June 1999, with a post-transplant survival > or = 9 months, good graft function and a regular clinical follow-up were enrolled for the study. A questionnaire that measured aspects of inactivity before and after liver transplantation had been applied., Results: Thirty-one of 41 patients were unable to work due end-stage liver disease before liver transplantation. Return to work was observed in 28 of 41 patients (68%) in a mean time of 5.9 months after the surgical procedure. Eleven of 28 active patients after liver transplant (39%) contribute significantly to family income. The reasons for inactivity after liver transplantation were: early retirement (n = 5), unemployment (n = 4), and physical disability (n = 4)., Conclusion: Successful liver transplantation not only improves the survival rate but allows patients to return to social function and workforce.