Endurance exercise training changes the limitation on muscle V ̇ O 2 max ${\dot{V}}_{{{\mathrm{O}}}_{\mathrm{2}}{\mathrm{max}}}$ in normoxia from the capacity to utilize O2 to the capacity to transport O2.

Maximal oxygen (O2 ) uptake ( V ̇ O 2 max ${\dot{V}}_{{{\mathrm{O}}}_{\mathrm{2}}{\mathrm{max}}}$ ) is an important parameter with utility in health and disease. However, the relative importance of O2 transport and utilization capacities in limiting muscle V ̇ O 2 max ${\dot{V}}_{{{\mathrm{O}}}_{\mathrm{2}}{\mathrm{max}}}$ before and after endurance exercise training is not well understood. Therefore, the present study aimed to identify the mechanisms determining muscle V ̇ O 2 max ${\dot{V}}_{{{\mathrm{O}}}_{\mathrm{2}}{\mathrm{max}}}$ pre- and post-endurance exercise training in initially sedentary participants. In five initially sedentary young males, radial arterial and femoral venous P O 2 ${P}_{{{\mathrm{O}}}_{\mathrm{2}}}$ (blood samples), leg blood flow (thermodilution), and myoglobin (Mb) desaturation (1 H nuclear magnetic resonance spectroscopy) were measured during maximal single-leg knee-extensor exercise (KE) breathing either 12%, 21% or 100% O2 both pre and post 8 weeks of KE training (1 h, 3 times per week). Mb desaturation was converted to intracellular P O 2 ${P}_{{{\mathrm{O}}}_{\mathrm{2}}}$ using an O2  half-saturation pressure of 3.2 mmHg. Pre-training muscle V ̇ O 2 max ${\dot{V}}_{{{\mathrm{O}}}_{\mathrm{2}}{\mathrm{max}}}$ was not significantly different across inspired O2 conditions (12%: 0.47 ± 0.10; 21%: 0.52 ± 0.13; 100%: 0.54 ± 0.01 L min-1 , all q > 0.174), despite significantly greater muscle mean capillary-intracellular P O 2 ${P}_{{{\mathrm{O}}}_{\mathrm{2}}}$ gradients in normoxia (34 ± 3 mmHg) and hyperoxia (40 ± 7 mmHg) than hypoxia (29 ± 5 mmHg, both q < 0.024). Post-training muscle V ̇ O 2 max ${\dot{V}}_{{{\mathrm{O}}}_{\mathrm{2}}{\mathrm{max}}}$ was significantly different across all inspired O2 conditions (12%: 0.59 ± 0.11; 21%: 0.68 ± 0.11; 100%: 0.76 ± 0.09 mmHg, all q < 0.035), as were the muscle mean capillary-intracellular P O 2 ${P}_{{{\mathrm{O}}}_{\mathrm{2}}}$ gradients (12%: 32 ± 2; 21%: 37 ± 2; 100%: 45 ± 7 mmHg, all q < 0.029). In these initially sedentary participants, endurance exercise training changed the basis of limitation on muscle V ̇ O 2 max ${\dot{V}}_{{{\mathrm{O}}}_{\mathrm{2}}{\mathrm{max}}}$ in normoxia from the mitochondrial capacity to utilize O2 to the capacity to transport O2 to the mitochondria. KEY POINTS: Maximal O2 uptake is an important parameter with utility in health and disease. The relative importance of O2 transport and utilization capacities in limiting muscle maximal O2 uptake before and after endurance exercise training is not well understood. We combined the direct measurement of active muscle maximal O2 uptake with the measurement of muscle intracellular P O 2 ${P}_{{{\mathrm{O}}}_{\mathrm{2}}}$ before and after 8 weeks of endurance exercise training. We show that increasing O2 availability did not increase muscle maximal O2 uptake before training, whereas increasing O2 availability did increase muscle maximal O2 uptake after training. The results suggest that, in these initially sedentary participants, endurance exercise training changed the basis of limitation on muscle maximal O2 uptake in normoxia from the mitochondrial capacity to utilize O2 to the capacity to transport O2 to the mitochondria.

Depressive symptoms, right ventricular function, and muscular strength are associated with peak oxygen uptake in patients with implantable left ventricular assist devices.

BACKGROUND: Left ventricular assist device (LVAD) implantation is among the most effective treatment options for patients with severe heart failure. Although previous studies have examined the factors related to peak oxygen uptake (peak VO2 ), they were limited by the few patients involved and their focus on medical and physical functions. Therefore, this study comprehensively examined the factors associated with peak VO2 , which is an important prognostic factor in patients with implantable LVADs. METHODS: Eighty-nine patients who underwent initial LVAD implantation and were eligible for cardiopulmonary exercise testing (CPX) between May 2014 and September 2021 were included. The patients' mean age was 48 ± 12 years, and 70% were males. Based on previous studies, the cut-off was set at 12 and 14 mL/kg/min for patients taking ß-blocker and those not taking ß-blockers, respectively. Furthermore, factors associated with peak VO2 were examined using multivariate logistic regression analysis. RESULTS: The mean time from surgery to CPX administration was 73 ± 40 days. The high group had a higher cardiac index, right ventricular stroke work index (RVSWI), and isometric knee extensor muscular strength and lower Patient Health Questionnaire-9 (PHQ-9) and B-type natriuretic peptide values than the low group. Multivariate logistic regression analysis showed that RVSWI and KEMS were positively correlated, whereas PHQ-9 was negatively associated with peak VO2 . CONCLUSION: Right ventricular function, depressive symptoms, and lower limb muscular strength were associated with exercise capacity in patients with implantable LVADs.

Cut-off values of preoperative knee extensor strength and hip abductor strength for predicting good walking ability after total knee arthroplasty.

INTRODUCTION: Total knee arthroplasty (TKA) reduces pain and improves physical function; however, not all patients have successful outcomes after surgery. To identify these patients would be critical information for improving rehabilitation programs. The purpose of this study was to clarify the cut-off values of lower extremity muscle strength for predicting postoperative good walking ability. MATERIALS AND METHODS: Timed Up and Go test of 105 patients was measured at 6 months postoperatively, and participants were divided into good (< 9.1 s) and poor (≥ 9.1 s) walking ability. Both sides of knee extensor strength (KES) and hip abductor strength (HAS) were measured using hand-held dynamometer preoperatively. Receiver operating characteristic (ROC) curve analysis was used to identify cut-off values for classifying the participants into the two groups. RESULTS: Of the 105 patients, 54 were allocated in the poor walking ability group, whereas 51 were allocated in the good walking ability group. KES and HAS were significantly greater in the good walking ability group than in the poor walking ability group. ROC curve analysis revealed that the cut-off value for KES was 0.79 Nm/kg (area under the curve (AUC) 0.68; sensitivity 64.7%; specificity 68.5%) on the involved side and 0.86 Nm/kg (AUC 0.73; sensitivity 84.6%; specificity 55.6%) on the uninvolved side, and for HAS was 0.57 Nm/kg (AUC 0.71; sensitivity 60.8%; specificity 71.7%) on the involved side and 0.61 Nm/kg (AUC 0.76; sensitivity 66.7%; specificity 77.4%) on the uninvolved side. CONCLUSION: The cut-off values of preoperative KES and HAS for predicting good walking ability after TKA are 0.79 Nm/kg on the involved side and 0.86 Nm/kg on the uninvolved side, and 0.57 Nm/kg on the involved side and 0.61 Nm/kg on the uninvolved side, respectively. We should provide enhanced pre- and post-operative rehabilitation programs for patients with muscle strength lower than these values.

A Longitudinal Study of the Physical Characteristics, Muscle-Tendon Structure Properties, and Skeletal Age in Preadolescent Boys.

OBJECTIVES: The purpose of this study was to examine longitudinal growth changes in physical characteristics, muscle-tendon structure properties, and skeletal age in preadolescent boys and to compare the relationship between the changes in physical characteristics and muscle-tendon properties and the changes in chronological and skeletal ages. METHODS: Fourteen prepubescent boys (10.9 ± 1.1 years old at the onset of the study) participated in this study over two years (yearly). Maximal muscle strength and maximal strain of tendon structure during ramp isometric contraction and muscle and tendon thickness for knee extensors and plantar flexors were measured. In addition, skeletal age was assessed using Tanner-Whitehouse three method. RESULTS: Changes in height, thigh length, and lower leg length were highly correlated with changes in skeletal age but not chronological age. However, changes in the morphological and mechanical properties of muscle and tendon structure were not significantly associated with changes in chronological and skeletal ages. CONCLUSION: The present preliminary results suggest that longitudinal growth changes in the long-axis of the body are highly correlated with skeletal age change, whereas those in the muscle-tendon structure properties were not.

Time to treat the tendon rupture induced by surgery: early hypertrophy of the patellar tendon graft site predicts strong quadriceps after ACLR with bone-patellar tendon-bone autograft.

PURPOSE: Quadriceps dysfunction is ubiquitous after anterior cruciate ligament reconstruction, especially when using bone-patellar tendon-bone (BPTB) autografts. The role of patellar tendon hypertrophy after graft harvest on knee extensor strength is unknown. The purpose of this study was to determine the predictive ability of patellar tendon (PT) and quadriceps muscle (Quad) cross-sectional area (CSA) on knee extensor strength 1-2 months after ACLR using BPTB autografts. METHODS: This is a cross-sectional analysis of a cohort 1-2 months after ACLR using BPTB autograft. Peak knee extensor torque, and PT and Quad CSA measured using ultrasound imaging, were collected in 13 males and 14 females. Simple linear regressions compared quadriceps strength index (QI) against limb symmetry index (LSI) in PT and Quad CSA. Multiple linear regressions with sequential model comparisons predicting peak knee extensor torque were performed for each limb. The base model included demographics. Quad CSA was added in the first model, then PT CSA was added in the second model. RESULTS: Both PT (p < 0.001, R2 = 0.693) and Quadriceps CSA (p = 0.013, R2 = 0.223) LSI had a positive linear relationship with QI. In the involved limb, addition of PT CSA significantly improved the model (R2 = 0.781, ΔR2 = 0.211, p for ΔR2 < 0.001). In the uninvolved limb, the addition of Quad CSA improved the model, but the addition of PT CSA did not. CONCLUSION: PT LSI was more predictive of QI than Quad CSA LSI. Involved limb PT CSA mattered more in predicting peak knee extensor torque than did Quad CSA, but in the uninvolved limb, Quad CSA was the most important predictor of peak knee extensor torque. Graft site patellar tendon hypertrophy is key for strong quadriceps early after ACLR. Early targeted loading via exercise to promote healing of the graft site patellar tendon may bring patients a step closer to winning their battle against quadriceps dysfunction. LEVEL OF EVIDENCE: Level I.

Limited preoperative knee extension in anterior cruciate ligament reconstruction using a hamstring tendon affects improvement of postoperative knee extensor strength.

PURPOSE: This study aimed to determine the factors affecting knee extensor strength 6 months after anterior cruciate ligament (ACL) reconstruction using autograft hamstring tendon. METHODS: 144 patients who could undergo regular follow-up after ACL reconstruction were divided into 2 groups: those with greater than 90% (Group A: n = 95) and less than 85% (Group B: n = 49) isokinetic knee contraction at 60°/s 6 months post-ACL reconstruction. Basic information, injury status, limited preoperative knee extension, and knee extensor strength at 3 and 6 months postoperatively were compared between the groups. Multivariate logistic analysis was performed and included variables that showed statistically significant differences between the groups in the univariate analysis. In addition, the cut-off value for the limb symmetry index (LSI) at 3 months postoperatively needed to exceed an LSI of 90% at 6 months postoperatively was calculated using the receiver operating characteristics curve. RESULTS: Age, preoperative waiting period, limited preoperative knee extension, and knee extensor strength at 3 months postoperatively were significantly different between the two groups. The multivariate logistic analysis showed that all the variables affected the improvement in knee extensor strength at 6 months postoperatively. Limited preoperative knee extension was the most significant factor (odds ratio: 15.1, 95% confidence interval: 2.57-118.56, p < 0.01). The LSI cut-off value at 3 months postoperatively was 72.0%. CONCLUSION: Key factors in achieving the necessary knee extensor strength criteria for return to sports at 6 months post-ACL reconstruction include addressing limited preoperative knee extension and achieving an LSI ≥ 72% in knee extensor strength at 3 months postoperatively. LEVEL OF EVIDENCE: Level III.

Outcome comparison of femoral nerve block and adductor canal block during anterior cruciate ligament reconstruction: adductor canal block may cause an unexpected decrease in knee flexor strength at 6 months postoperatively.

INTRODUCTION: Peripheral nerve blocks are frequently used in anterior cruciate ligament (ACL) reconstruction. While femoral nerve block (FNB) has been associated with knee extensor strength reduction in the early postoperative period, no consistent view of knee extensor strength several months after ACL reconstruction exists. This study aimed to compare the impact of intraoperative FNB and adductor canal block (ACB) during ACL reconstruction on knee extensor strength at 3 and 6 months postoperatively. MATERIALS AND METHODS: This retrospective study included 108 patients divided into FNB (70 patients) and ACB (38 patients) groups based on their postoperative pain management methods. Knee joint extensor and flexor strength were measured at 3 and 6 months postoperatively, using BIODEX at angular velocities of 60°/s and 180°/s. From these results, peak torque, limb symmetry index (LSI), peak knee extensor torque (time to peak torque and angle of peak torque), hamstrings-to-quadriceps (HQ) ratio, and amount of work were computed for two-group comparison. RESULTS: There were no statistically significant differences in peak torque, LSI of knee extensor strength, HQ ratio, and amount of work between the two groups. However, maximum knee extension torque at 60°/s occurred significantly later in the FNB than in the ACB group at 3 months postoperatively. Additionally, the LSI of the knee flexor at 6 months postoperatively was significantly lower in the ACB group. CONCLUSIONS: In ACL reconstruction, FNB may delay the time to peak torque for knee extension at 3 months postoperatively, which is likely to improve over the treatment course. In contrast, ACB may result in unexpected loss of knee flexor strength at 6 months postoperatively and should be considered with caution. LEVEL OF EVIDENCE: Level III.

Improvements in asymmetry in knee flexion motion during landing are associated with the postoperative period and quadriceps strength after anterior cruciate ligament reconstruction.

This study investigated the relationship between quadriceps strength and knee kinematics during a drop vertical jump (DVJ) at 6, 9 and 12 months after anterior cruciate ligament reconstruction (ACLR) in 9 male and 22 female athletes (16.6 ± 2.1 years old). Isokinetic quadriceps strength was measured by a dynamometer (Biodex System 3). Knee flexion excursion was assessed using two-dimensional analysis. Knee flexion excursion at 6 months was significantly smaller in the involved limb than in the uninvolved limb independent of quadriceps strength (56.7° ± 9.3°, 63.4° ± 11.4°, P < 0.001). At 9 months, only the low quadriceps strength group demonstrated a similar interlimb difference (57.2°± 12.3°, 63.3° ± 10.5°, P < 0.001). At 12 months, there was no significant interlimb difference in knee flexion excursion regardless of quadriceps strength. These findings indicate that restoration in symmetrical knee flexion excursion during a DVJ requires rehabilitation as well as quadriceps strength.

Knee-extensor strength, symptoms, and need for surgery after two, four, or six exercise sessions/week using a home-based one-exercise program: a randomized dose-response trial of knee-extensor resistance exercise in patients eligible for knee replacement (the QUADX-1 trial).

OBJECTIVE: To investigate firstly the efficacy of three different dosages of one home-based, knee-extensor resistance exercise on knee-extensor strength in patients eligible for knee replacement, and secondly, the influence of exercise on symptoms, physical function and decision on surgery. METHOD: One-hundred and forty patients eligible for knee replacement were randomized to three groups: 2, 4 or 6 home-based knee-extensor resistance exercise-sessions per week (group 2, 4 and 6 respectively) for 12 weeks. PRIMARY OUTCOME: isometric knee-extensor strength. SECONDARY OUTCOMES: Oxford Knee Score, Knee injury and Osteoarthritis Outcome Score, average knee pain last week (0-10 numeric rating scale), 6-min walk test, stair climbing test, exercise adherence and "need for surgery". RESULTS: Primary analysis: Intention-to-treat analysis of 140 patients did not find statistically significant differences between the groups from baseline to after 12 weeks of exercise in isometric knee-extensor strength: Group 2 vs 4 (0.003 Nm/kg (0.2%) [95% CI -0.15 to 0.15], P = 0.965) and group 4 vs 6 (-0.04 Nm/kg (-2.7%) [95% CI -0.15 to 0.12], P = 0.628). Secondary analysis: Intention-to-treat analyses showed statistically significant differences between the two and six sessions/week groups in favor of the two sessions/week group for Oxford Knee Score: 4.8 OKS points (15.2%) [1.3 to 8.3], P = 0.008) and avg. knee pain last week (NRS 0-10): -1.3 NRS points (-19.5%) [-2.3 to -0.2], P = 0.018. After the 12-week exercise intervention, data were available for 117 patients (N = 39/group): 38 (32.5%) patients wanted surgery and 79 (67.5%) postponed surgery. This was independent of exercise dosage. CONCLUSION: In patients eligible for knee-replacement we found no between-group differences in isometric knee extensor strength after 2, 4 and 6 knee-extensor resistance exercise sessions per week. We saw no indication of an exercise dose-response relationship for isometric knee-extensor strength and only clinically irrelevant within group changes. For some secondary outcome (e.g., KOOS subscales) we found clinically relevant within group changes, which could help explain why only one in three patients decided to have surgery after the simple home-based exercise intervention. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02931058. Preprint: https://doi.org/10.1101/2021.04.07.21254965.

Factors associated with early postoperative exercise tolerance after living-donor liver transplantation.

BACKGROUND: Physical dysfunction, including exercise intolerance, is a major factor for delayed societal reintegration for patients who underwent living-donor liver transplantation (LDLT). However, what may contribute to early postoperative physical function is not well known. The purpose of this study is to elucidate the perioperative factors affecting early posttransplant exercise intolerance. METHODS: 103 consecutive patients who underwent LDLT were enrolled, and 68 patients were retrospectively analyzed. We examined the relationship between postoperative exercise tolerance evaluated by a 6-minute walking distance (6MWD) at discharge after surgery and demographic data, surgical information, preoperative physical function, clinical course, and the postoperative decline in physical function with univariate and multivariate analyses. RESULTS: Almost all patients were discharged within 3 months after surgery. The postoperative 6MWD was 408 ± 94 m (68 [61-84]% of the predicted value), and patients who had a low %6MWD at discharge had significantly lower preoperative physical function than patients who had a high %6MWD at discharge (grip strength: 29.8 ± 8.9 kgf vs. 23.0 ± 8.8 kgf, P < .01, knee extensor strength: 138.9 ± 59.4 Nm vs. 95.2 ± 42.1 Nm, P < .01). Multivariate analysis revealed that preoperative knee extensor strength (standardized ß = 0.35, P < .01) and first postoperative walking day (standardized ß = -0.22, P = .04) were independently associated with the postoperative %6MWD. CONCLUSION: These results suggest that maintaining preoperative muscle strength and allowing for early postoperative mobilization might help to enhance the recovery of physical function and facilitate the patient's social reintegration after LDLT.

Evaluation of indices for predicting recovery of exercise tolerance in patients surviving allogenic hematopoietic stem cell transplantation.

PURPOSE: Decline in physical function in the early stage after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a major challenge. Exercise tolerance tests, such as the 6-min walk test, are useful markers for predicting exercise tolerance and various other traits, including cardiometabolic risk and non-relapse mortality. This retrospective cohort study aimed to investigate and identify predictors of recovery of exercise tolerance in the early stage after allo-HSCT. METHODS: Ninety-eight patients were classified into recovery and non-recovery groups according to the median 6-min walk distance (6MWD) at discharge. RESULTS: Logistic regression analysis revealed that pre-post change in knee extensor strength (ΔKES) and hematopoietic cell transplantation comorbidity index were useful predictors of recovery of exercise tolerance at discharge and moderate predictors of 6MWD recovery in the early post-transplant period. Receiver operating characteristic analysis showed that pre-transplant ΔKES was an accurate predictor of 6MWD recovery in the early post-transplant period. The cutoff point for ΔKES calculated using the Youden index was - 1.17 Nm/kg. CONCLUSIONS: The results of this study emphasize the importance of the need for programs designed to prevent muscle weakness in the early period after allo-HSCT. The results from markers of recovery of exercise tolerance are promising and can be used for patient education in rehabilitation programs after allo-HSCT.

Association of Knee Extensor Muscle Strength and Cardiorespiratory Fitness With Bone Stiffness in Japanese Adults: A Cross-sectional Study.

BACKGROUND: Knee extensor muscle strength and cardiorespiratory fitness (CRF) are major components of physical fitness. Because the interactive association of knee extensor muscle strength and CRF with bone health remains unclear, we aimed to investigate such association in Japanese adults. METHODS: Altogether, 8,829 Japanese adults (3,731 men and 5,098 women) aged ≥45 years completed the maximum voluntary knee extension test, submaximal exercise test, medical examination, and a questionnaire on lifestyle habits. Using an osteo-sono assessment index, low bone stiffness tendency was defined as 80% under the young-adults mean. Multivariable odds ratios (ORs) and 95% confidence intervals (CIs) were calculated after confounder adjustment. RESULTS: Overall, 542 men (14.5%) and 978 women (19.2%) had low bone stiffness tendency. We observed an inverse association between muscle strength and low bone stiffness tendency after adjustment for CRF in both sexes (P for linear trend <0.001). Compared with the lowest CRF, the multivariable ORs for low bone stiffness tendency in the highest CRF were 0.47 (95% CI, 0.36-0.62) for men and 1.05 (95% CI, 0.82-1.35) for post-menopausal women (P < 0.001 and P = 0.704, respectively). No interactive association between muscle strength and CRF for low bone stiffness tendency existed in both sexes and irrespective of menopausal status. CONCLUSION: Knee extensor muscle strength and CRF were associated additively, not synergistically, with bone health. Maintaining high levels of both physical fitness components may improve musculoskeletal health in the cohort. The relationship between physical fitness and bone status should be longitudinally investigated in the future.

Nutritional Factors Related to Muscle Weakness 1 Year after Total Hip Arthroplasty: A Case-Control Study.

OBJECTIVES: Prolonged muscle weakness after total hip arthroplasty (THA) remains a problem. Despite increasing physical activity up to 3 years after surgery, muscle strength was decreased to 80-90% of the healthy side 2 years after THA. The objective of the present study was to identify the nutritional factors related to muscle weakness 1 year after THA. METHODS: Persons who underwent THA were divided into 2 groups according to the cutoff point of knee extensor strength that represents functional limitation: a normal-strength group of 71 persons and a muscle weakness group of 91 persons. The investigators assessed lower limb isometric strength, the 10-m timed gait test, and daily intakes of energy and nutrients from preoperative to 1 year after THA. The differences in nutrient intakes between the 2 groups (normal-strength group and muscle weakness group) were examined by multiple logistic regression analysis. RESULTS: There was a significant difference between the groups in energy intake. Daily protein intake was related to knee extension strength gain above the cutoff point 1 year after THA. CONCLUSIONS AND IMPLICATIONS: The present study suggested that to prevent prolonged muscle weakness after THA, a sufficient protein intake as well as an exercise intervention may be needed even half a year or after.

Comparison of the Acute Effects of Foam Rolling with High and Low Vibration Frequencies on Eccentrically Damaged Muscle.

Previous research has shown that vibration foam rolling (VFR) on damaged muscle shows greater improvement in muscle soreness and range of motion (ROM) compared with foam rolling (FR) without vibration. However, the effect of frequency in VFR on muscle soreness and loss of function caused by damaged muscles is unknown. The purpose of this study was to compare the acute effects of 90-s low-frequency (LF)- and high-frequency (HF)-VFR intervention on ROM, muscle soreness, muscle strength, and performance of eccentrically damaged muscle. Study participants were sedentary healthy adult volunteers (n = 28) who performed a bout of eccentric exercise of the knee extensors with the dominant leg and received 90-s LF-VFR or HF-VFR intervention of the quadriceps 48 h after the eccentric exercise. The dependent variables were measured before the eccentric exercise (baseline) and before (pre-intervention) and after VFR intervention (post-intervention) 48 h after the eccentric exercise. The results showed that both LF-VFR and HF-VFR similarly (p < 0.05) improved the knee flexion ROM (11.3 ± 7.2%), muscle soreness at palpation (-37.9 ± 17.2%), and countermovement jump height (12.4 ± 12.9%). It was concluded that it was not necessary to perform VFR with a high frequency to improve muscle soreness and function.

Nitrate-rich beetroot juice ingestion reduces skeletal muscle O2 uptake and blood flow during exercise in sedentary men.

Dietary nitrate supplementation has been shown to reduce pulmonary O2 uptake during submaximal exercise and enhance exercise performance. However, the effects of nitrate supplementation on local metabolic and haemodynamic regulation in contracting human skeletal muscle remain unclear. To address this, eight healthy young male sedentary subjects were assigned in a randomized, double-blind, crossover design to receive nitrate-rich beetroot juice (NO3, 9 mmol) and placebo (PLA) 2.5 h prior to the completion of a double-step knee-extensor exercise protocol that included a transition from unloaded to moderate-intensity exercise (MOD) followed immediately by a transition to intense exercise (HIGH). Compared with PLA, NO3 increased plasma levels of nitrate and nitrite. During MOD, leg V̇O2 and leg blood flow (LBF) were reduced to a similar extent (∼9%-15%) in NO3. During HIGH, leg V̇O2 was reduced by ∼6%-10% and LBF by ∼5%-9% (did not reach significance) in NO3. Leg V̇O2 kinetics was markedly faster in the transition from passive to MOD compared with the transition from MOD to HIGH both in NO3 and PLA with no difference between PLA and NO3. In NO3, a reduction in nitrate and nitrite concentration was detected between arterial and venous samples. No difference in the time to exhaustion was observed between conditions. In conclusion, elevation of plasma nitrate and nitrate reduces leg skeletal muscle V̇O2 and blood flow during exercise. However, nitrate supplementation does not enhance muscle V̇O2 kinetics during exercise, nor does it improve time to exhaustion when exercising with a small muscle mass. KEY POINTS: Dietary nitrate supplementation has been shown to reduce systemic O2 uptake during exercise and improve exercise performance. The effects of nitrate supplementation on local metabolism and blood flow regulation in contracting human skeletal muscle remain unclear. By using leg exercise engaging a small muscle mass, we show that O2 uptake and blood flow are similarly reduced in contracting skeletal muscle of humans during exercise. Despite slower V̇O2 kinetics in the transition from moderate to intense exercise, no effects of nitrate supplementation were observed for V̇O2 kinetics and time to exhaustion. Nitrate and nitrite concentrations are reduced across the exercising leg, suggesting that these ions are extracted from the arterial blood by contracting skeletal muscle.

Cardiac rehabilitation program improves exercise capacity in heart transplantation recipients regardless of marginal donor factors.

Cardiac rehabilitation (CR) is recommended to improve exercise capacity after heart transplantation (HTx); however, the effects of marginal donor factors are unclear. Forty-one recipients participated in a 3-month CR program early after HTx (mean age 39 ± 14 years; 88% male). Patients were divided into marginal (≥ 2 marginal donor factors; n = 24) and control groups (< 2 marginal donor factors; n = 17). We examined donor and recipient factors related to change in peak oxygen uptake (peak VO2) during the CR program using multiple linear regression analysis. Baseline characteristics were similar between groups, although the mean age was higher in the marginal group (43 ± 13 vs. 34 ± 14 years, p = 0.043). Peak VO2 and knee extensor muscular strength (KEMS) improved significantly in both groups (p < 0.05), but there were no observed inter-group differences. Multiple analysis revealed change in KEMS (ß = 0.52, 95% CI = 0.023-1.01) as an independent predictor of change in peak VO2 after adjustment for recipients' age, sex, and CR attendance frequency (adjusted R2 = 0.25, p = 0.0084), whereas marginal donor factors were not a predictor (p = 0.76). The CR program improved exercise capacity in HTx recipients regardless of marginal donor factors, suggesting that recipients of marginal donor hearts should be referred to CR programs.

Ratio of serum creatinine to cystatin C is related to leg strength in predialysis CKD patients.

BACKGROUND AND OBJECTIVES: Chronic kidney disease (CKD) patients have lower levels of physical function. Especially, leg strength is important for daily living and preventing falls. However, physical function screenings are difficult to perform at clinical sites. To find clinically useful method to evaluate physical function in predialysis CKD patients, we tried to evaluate the relationship between the ratio of serum creatinine to serum cystatin C (Cre/CysC), and knee extensor muscle strength/body weight (KEMS) which reflects their leg strength. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: We recruited 147 outpatients with CKD (87 men; mean age, 61.6 ± 9.8 years; mean eGFRcreat, 40.7 ± 12.9 mL/min/1.73m2) in this cross-sectional study. KEMS was assessed using a wire strain gauge dynamometer. Skeletal muscle mass and body fat mass were assessed by bioelectrical impedance analysis. RESULTS: The mean value of Cre/CysC was 1.01 ± 0.18. The mean value of KEMS was 1.60 ± 0.47 Nm/kg. In multivariate linear regression analysis, skeletal muscle mass (p < 0.01), body fat mass (p < 0.01), hemoglobin (p = 0.01), and Cre/CysC (p < 0.01) was independently related to KEMS. The correlation between Cre/CysC and KEMS is stronger in high quantile of Cre/CysC. CONCLUSIONS: In predialysis CKD patients, KEMS showed lower as CKD stage advanced. Cre/CysC is significantly related to KEMS independently. Cre/CysC may be an alternative marker for leg strength in CKD patients and even more valuable to utilize in cases with high Cre/CysC.

Acute effects of repetitive peripheral magnetic stimulation following low-intensity isometric exercise on muscle swelling for selective muscle in healthy young men.

Repetitive peripheral magnetic stimulation (rPMS) is a non-invasive stimulator that can induce strong muscle contraction in selective regions. This study aimed to measure acute changes in skeletal muscle thickness induced by rPMS following a low-intensity exercise. Fifteen healthy young men performed an isometric knee extensor exercise at 30% of maximum strength consisting of three sets of 10 contractions on their dominant leg. rPMS was then applied on the vastus lateralis (VL) at the maximum intensity of the rPMS device. Muscle thicknesses of the rectus femoris (RF) and VL were measured using an ultrasound device and were compared among baseline, post-exercise, and post-rPMS. There were significant increases in muscle thickness of both the RF and VL post-exercise compared with baseline values (RF: baseline; 24.7 ± 2.4, post-exercise; 25.3 ± 2.4 mm, p = .034, VL: baseline; 27.0 ± 2.8, post-exercise; 27.4 ± 2.8 mm, p = .006). Compared with post-exercise, there was a significant increase post-rPMS in only the VL (VL: post-rPMS; 28.3 ± 2.9 mm, p = .002). These findings suggest that low-intensity isometric exercise can induce acute increases in muscle thickness (muscle swelling) in synergist muscles, and rPMS following exercise can induce further acute muscle swelling via repetitive muscle contraction.

The relationship between prescribed pre-operative knee-extensor exercise dosage and effect on knee-extensor strength prior to and following total knee arthroplasty: a systematic review and meta-regression analysis of randomized controlled trials.

OBJECTIVE: The aim of this systematic review was to evaluate the relationship between prescribed knee-extensor strength exercise dosage in pre-operative exercise intervention and the effect on knee-extensor muscle strength prior to and following TKA. Additional meta-analyses report the effect of pre-habilitation on outcomes prior to and following TKA. DESIGN: A systematic literature search was performed including RCT's evaluating the effect of pre-operative exercise prior to and following TKA. Meta-regression analysis was performed to evaluate the dose-response relationship between prescribed exercise dose and the pooled effect, measured as standardized mean difference (SMD). The prescribed exercise dose was quantified using a formula accounting for as many exercise descriptors as possible. Risk of bias in the included trials was assessed using the Cochrane Risk of Bias Tool. RESULTS: Twelve trials with 616 patients were included. Meta-regression analysis showed no relationship between prescribed pre-operative knee-extensor exercise dosage and change in knee-extensor strength neither prior to (slope 0.0005 [95%CI -0.007 to 0.008]) or 3 months following TKA (slope 0.0014 [95%CI -0.006 to 0.009]). Prior to TKA, a moderate effect favoring pre-operative exercise for increase in knee-extensor strength was found (SMD 0.50 [95%CI 0.12 to 0.88]), but not at 3 months following TKA (SMD -0.01 [95%CI -0.45 to 0.43]). Risk of bias was generally assessed as unclear. CONCLUSION: Meta-regression analysis of existing trials suggests no relationship between the prescribed pre-operative knee-extensor exercise dosage and the change in knee-extensor strength observed prior to and following TKA. Pre-operative exercise including knee-extensor muscle strength exercise increased knee-extensor strength moderately prior to but not 3 months following TKA. PROTOCOL REGISTRATION: PROSPERO ID (CRD42018076308) (http://www.crd.york.ac.uk/PROSPERO/).

Effect of the severity of acute graft-versus-host disease on physical function after allogeneic hematopoietic stem cell transplantation.

PURPOSE: The purpose of this study was to retrospectively investigate the effect of the severity of acute graft-versus-host disease (GVHD) on physical function after allogeneic hematopoietic stem cell transplantation (allo-HSCT). METHODS: 76 patients were included as subjects of this study. Severity of acute GVHD was classified according to the method defined by Grucksberg. To evaluate physical function, the knee extensor strength and six-minute walk distance (6MWD) were performed. RESULTS: Among these patients, 54% developed acute GVHD; of these, 32%, 54%, and 15% of patients had grade I, grade II, and grades III-IV GVHD, respectively. In the grade I-II groups, mild acute GVHD following allo-HSCT resulted in a gradual decline in physical function, which improved at discharge. However, in cases of severe acute GVHD, physical function deteriorated, implementation of rehabilitation became difficult, and the decline in physical function persisted even at discharge. CONCLUSION: These results indicate that severe acute GVHD negatively affects physical function leading to longer hospital days because of inadequate rehabilitation interventions.