Medicine & Science in Sports & Exercise

Persistent Impairment in Cardiopulmonary Fitness after Breast Cancer Chemotherapy Purpose Anthracycline chemotherapy (AC) is associated with acute reductions in cardiopulmonary fitness (V˙O2peak). We sought to determine whether changes in V˙O2peak and cardiac function persisted at 12 months post-AC completion, and whether changes in cardiac function explain the heightened long-term heart failure risk. Methods Women with breast cancer scheduled for AC (n = 28) who participated in a nonrandomized trial of exercise training (ET; n = 14) or usual care (UC; n = 14) during AC completed a follow-up evaluation 12 months post-AC completion (16 months from baseline). At baseline, 4 months, and 16 months, participants underwent a resting echocardiogram (left ventricular ejection fraction; global longitudinal strain), a blood sample (troponin; B-type natriuretic peptide), a cardiopulmonary exercise test, and cardiac MRI measures of stroke volume (SV), heart rate, and cardiac output (Qc) at rest and during intense exercise. Results Seventeen women (UC, n = 8; ET, n = 9) completed evaluation at baseline, 4 months, and 16 months. At 4 months, AC was associated with 18% and 6% reductions in V˙O2peak in the UC and ET groups, respectively, which persisted at 16 months (UC, −16%; ET, −7%) and was not attenuated by ET (interaction, P = 0.10). Exercise Qc was lower at 16 months compared with baseline and 4 months (P < 0.001), which was due to a blunted augmentation of SV during exercise (P = 0.032; a 14% reduction in peak SV), with no changes in heart rate response. There was a small reduction in resting left ventricular ejection fraction (baseline to 4 months) and global longitudinal strain (between 4 and 16 months) and an increase in troponin (baseline to 4 months), but only exercise Qc was associated with V˙O2peak (R2 = 0.47, P < 0.01). Conclusion Marked reductions in V˙O2peak persisted 12 months after anthracycline-based chemotherapy, which was associated with impaired exercise cardiac function. Clinical Trial Registration: ACTRN12616001602415.

Effect of Creatine Supplementation on the Airways of Youth Elite Soccer Players Introduction Owing to its well-established ergogenic potential, creatine is a highly popular food supplement in sports. As an oral supplement, creatine is considered safe and ethical. However, no data exist on the safety of creatine on lung function in athletes. The aim of this project was to evaluate the effects of a standard course of creatine on the airways of youth elite athletes. Methods Nineteen elite soccer players, 16–21 yr old, completed a stratified, randomized, double-blind, placebo-controlled, parallel-group trial. The creatine group (n = 9) ingested 0.3 g·kg−1⋅d−1 of creatine monohydrate (CM) for 1 wk (loading phase) and 5 g·d−1 for 7 wk (maintenance phase), and the placebo group (n = 10) received the same dosages of maltodextrin. Airway inflammation (assessed by exhaled nitric oxide, FENO) and airway responsiveness (to dry air hyperpnoea) were measured pre- and postsupplementation. Results Mild, unfavorable changes in FENO were noticed by trend over the supplementation period in the CM group only (P = 0.056 for interaction, η2 = 0.199), with a mean group change of 9 ± 13 ppb in the CM group versus −5 ± 16 ppb in the placebo group (P = 0.056, d = 0.695). Further, the maximum fall in forced expiratory volume in 1 s after dry air hyperpnoea was larger by trend postsupplementation in the CM group compared with the placebo group: 9.7% ± 7.5% vs 4.4% ± 1.4%, respectively (P = 0.070, d = 0.975). These adverse effects were more pronounced when atopic players only (n = 15) were considered. Conclusion On the basis of the observed trends and medium to large effect sizes, we cannot exclude that creatine supplementation has an adverse effect on the airways of elite athletes, particularly in those with allergic sensitization. Further safety profiling of the ergogenic food supplement is warranted.

Testosterone and Resistance Training Improve Muscle Quality in Spinal Cord Injury Purpose Spinal cord injury (SCI) negatively impacts muscle quality and testosterone levels. Resistance training (RT) has been shown to increase muscle cross-sectional area (CSA) after SCI, whereas testosterone replacement therapy (TRT) has been shown to improve muscle quality in other populations. The purpose of this pilot study was to examine if the combined effects of these interventions, TRT + RT, may maximize the beneficial effects on muscle quality after SCI. Methods Twenty-two SCI subjects randomized into either a TRT + RT (n = 11) or TRT (n = 11) intervention for 16 wk. Muscle quality measured by peak torque (PT) at speeds of 0°·s−1 (PT-0°), 60°·s−1 (PT-60°), 90°·s−1 (PT-90°), and 180°·s−1 (PT-180°), knee extensor CSA, specific tension, and contractile speed (rise time [RTi], and half-time to relaxation [½TiR]) was assessed for each limb at baseline and postintervention using 2 × 2 mixed models. Results After 16 wk, subjects in the TRT + RT group increased PT-0° (48.4%, P = 0.017), knee extensor CSA (30.8%, P < 0.0001), and RTi (17.7%, P = 0.012); with no significant changes observed in the TRT group. Regardless of the intervention, changes to PT-60° (28.4%, P = 0.020), PT-90° (26.1%, P = 0.055), and PT-180° (20.6%, P = 0.09) for each group were similar. Conclusions The addition of mechanical stress via RT to TRT maximizes improvements to muscle quality after complete SCI when compared with TRT administered alone. Our evidence shows that this intervention increases muscle size and strength while also improving muscle contractile properties.

Bone Biomarker Response to Walking under Different Thermal Conditions in Older Adults Endurance exercise can cause a decrease in serum ionized calcium (iCa) and increases in parathyroid hormone (PTH) and c-terminal telopeptide of type I collagen (CTX), which may be due to Ca loss in sweat. Purpose This study aimed to determine whether exercise in a warm environment exaggerates the decrease in iCa and increases in PTH and CTX compared with a cool environment in older adults. Methods Twelve women and men 61–78 yr old performed two identical 60-min treadmill bouts at ~75% of maximal heart rate under warm and cool conditions. Serum iCa, PTH, and CTX were measured every 15 min starting 15 min before and continuing for 60 min after exercise. Sweat Ca loss was estimated from sweat volume and sweat Ca concentration. Results Sweat volume was low and variable; there were no differences in sweat volume or Ca concentration between conditions. iCa decreased after 15 min of exercise, and the change was similar in both conditions. Increases in PTH (warm: 16.4, 95% confidence interval [CI] = 6.2, 26.5 pg·mL−1; cool: 17.3, 95% CI = 8.1, 26.4 pg·mL−1) and CTX (warm: 0.08, 95% CI = 0.05, 0.11 ng·mL−1; cool: 0.08, 95% CI = 0.01, 0.16 ng·mL−1) from before to immediately after exercise were statistically significant and similar between conditions. Adjusting for plasma volume shifts did not change the results. Conclusion The increases in PTH and CTX, despite the low sweat volume, suggest that dermal Ca loss is not a major factor in the decrease in iCa and increases in PTH and CTX observed during exercise in older adults.

Objectively Measured Physical Activity Is Associated with Vertebral Size in Midlife Background Vertebral fractures reduce the quality of life and are a major burden to the health care sector. Small vertebral size is associated with increased vertebral fracture risk. Previous studies have investigated the relationship between physical activity (PA) and vertebral size, but their results seem somewhat contradictory. In this population-based birth cohort study, we aimed to evaluate the relationship between objectively measured PA and vertebral size. Methods The study population consisted of 1202 cohort participants who underwent PA and vertebral size measurements at the age of 46 to 48 yr. Moderate-to-vigorous PA (MVPA, ≥3.5 METs) was measured by a wrist-worn accelerometer (Polar Active; Polar Electro, Finland) for 14 d. The vertebral axial cross-sectional area (CSA) of the L4 vertebra was measured and calculated from lumbar magnetic resonance imaging scans at 46 to 48 yr. We analyzed the association between the daily amount of MVPA (min·d−1) and vertebral CSA using multivariable linear regression analysis. Results The daily amount of MVPA was significantly and positively associated with CSA in both sexes. For every minute per day of MVPA, men had 0.71 mm2 (95% confidence interval, 0.36–1.06) and women 0.90 mm2 (95% confidence interval, 0.58–1.21) larger CSA. Conclusions Physical activity of at least moderate intensity is positively associated with vertebral size and may thus prevent future vertebral fractures.

Sedentary Time and White Matter Hyperintensity Volume in Older Adults Purpose Cerebrovascular disease in the form of white matter hyperintensities (WMH) increases with age and is associated separately with sedentary time and reduced kidney function. A better understanding of the relationships among these variables would help clarify whether sedentary time should be considered more closely in older adults at particular levels of kidney function to reduce the risk of WMH. Methods We analyzed information from 94 healthy community-dwelling older adults to determine the association of sedentary time and WMH in nondemented, nondepressed older adults, and whether level of kidney function was an effect modifier of the relationship between sedentary time and WMH. Sedentary behavior was measured using the Sedentary Behavior Questionnaire. White matter hyperintensity was assessed using whole-brain 3T magnetic resonance imaging T1- and T2-weighted images. Kidney function was calculated by the epi-chronic kidney disease formula for estimated glomerular filtration rate (eGFR). Exposures or predictors were sedentary time, age, sex, education in years, Framingham stroke risk 10-yr prediction score, and eGFR. The analytical approach was multiple linear regression. Results Adjusting for age, sex, education in years, Framingham stroke risk 10-yr prediction score, greater sedentary time was associated with greater WMH but this effect was dependent on level of eGFR (sedentary time–eGFR interaction b = −0.0005, P = 0.022). At eGFR values of 69, 81, and 93 mL·min−1 per 1.73 m2 (the 25th, 50th, and 75th percentiles), sedentary time b coefficients were b = 0.021 (95% confidence interval [CI], 0.011–0.031), b = 0.015 (95% CI, 0.008–0.022), and b = 0.009 (95% CI, 0.003–0.016). The effect weakened linearly as eGFR increased, with no significant association at eGFR ≥97 mL·min−1 per 1.73 m2. Conclusions Findings suggest that sedentary time is associated with WMH in persons with an eGFR ≤96 mL·min−1 per 1.73 m2 and that this association is stronger with lower levels of kidney function.

Shared Neuromuscular Performance Traits in Military Personnel with Prior Concussion Concussions are common in military personnel and may result in increased risk of musculoskeletal injury. One plausible explanation for this risk could be that neuromotor deficiencies enhance injury risk after a concussion through altered muscular activation/contraction timing. Purpose To compare military personnel with at least one concussion during the past 1 month to 2 yr (CONCUSSED) to military branch-matched, age-matched, and Special Operations Forces group–matched controls (CONTROL) on physiological, musculoskeletal, and biomechanical performance. Methods A total of 48 (24 CONCUSSED, 24 CONTROL) male Air Force and Naval Special Warfare Operators age 19 to 34 yr participated in the study. Participants self-reported demographics/injury history and completed the following assessments: 1) physiological—body composition, anaerobic power and capacity, aerobic capacity and lactate threshold; 2) musculoskeletal—lower extremity isokinetic strength testing, including time to peak torque; and 3) biomechanical—single-leg jump and landing task, including landing kinematics of the hip, knee and ankle. A machine learning decision tree algorithm (C5.0) and one-way ANOVA were used to compare the two groups on these outcomes. Results Despite nonsignificant differences using ANOVA, the C5.0 algorithm revealed CONCUSSED demonstrated quicker time to peak knee flexion angle during the single-leg landing task (≤0.170 s; CONCUSSED: n = 22 vs CONTROL: n = 14), longer time to peak torque in knee extension isokinetic strength testing (>500 ms; CONCUSSED: n = 18 vs CONTROL: n = 4) and larger knee flexion angle at initial contact (>7.7°; CONCUSSED: n = 18 vs CONTROL: n = 2). Conclusion The findings supported the hypothesis that CONCUSSED military personnel would demonstrate altered neuromuscular control in landing strategies and muscular activation. Future research should assess prospectively neuromuscular changes after a concussion and determine if these changes increase risk of subsequent musculoskeletal injuries.

Loading Behaviors Do Not Match Loading Abilities Postanterior Cruciate Ligament Reconstruction Purpose Strategies that underload the surgical limb after anterior cruciate ligament reconstruction (ACLr) are observed in submaximal tasks. It is not known what underlies these strategies in early rehabilitation. The purpose of this study was to determine if underloading can be attributed to the inability to meet task demands with and without attention to limb loading or learned behavior. Methods Twenty individuals (110.6 [18.1] days) post-ACLr and 20 healthy individuals (CTRL) participated in this study. Participants performed standing, sit-to-stand, and squat tasks under natural, instructed, and feedback conditions. Limb-loading symmetry was calculated as the between-limb ratio of vertical ground reaction force impulse during each task. General Linear Model repeated-measures analysis, 2 (group) × 3 (condition), determined the effects of group and condition on limb-loading symmetry for each task. Results Significant interactions were observed for each task (all P < 0.001). Compared with CTRL, ACLr exhibited greater asymmetry during natural (deficits: standing, 10%, P = 0.001; sit-to-stand, 25%, P < 0.001; squat, 15%, P < 0.001) and instructed (deficits: sit-to-stand, 13%, P = 0.001; squat, 8%, P = 0.04), but not feedback conditions. The CTRL maintained symmetry across conditions and tasks. Anterior cruciate ligament reconstruction exhibited greater asymmetry in natural compared with instructed (deficits: standing, 11%, P < 0.001; sit-to-stand, 14%, P < 0.001; squat, 8%, P = 0.001) and feedback (deficits: standing, 10%, P = 0.001; sit-to-stand, 21%, P < 0.001; squat, 15%, P < 0.001) conditions. Conclusions The presence of loading asymmetries in natural but not feedback conditions indicates that individuals 3 months post-ACLr shift loading away from surgical limb despite the ability to meet task demands which may be suggestive of nonuse behavior. Even when instructed to load symmetrically, individuals continued to exhibit some degree of asymmetry.

Effects of Exercise on Stress-induced Attenuation of Vaccination Responses in Mice Studies suggest that exercise can improve vaccination responses in humans. Chronic stress can lead to immunosuppression, and there may be a role for exercise in augmenting immune responses. Purpose To investigate the effects of acute eccentric exercise (ECC) and voluntary wheel exercise training (VWR) on antibody and cell-mediated immune responses to vaccination in chronically stressed mice. We hypothesized that both ECC and VWR would attenuate chronic stress-induced reductions in vaccination responses. Methods Mice were randomized into four groups: control (CON), stress (S)-ECC, S-VWR, and S-sedentary (SED). Stressed groups received chronic restraint stress for 6 h·d−1, 5 d·wk−1 for 3 wk. After the first week of stress, S-ECC were exercised at 17 m·min−1 speed at −20% grade for 45 min on a treadmill and then intramuscularly injected with 100 μg of ovalbumin (OVA) and 200 μg of alum adjuvant. All other groups were also vaccinated at this time. Stress-VWR mice voluntarily ran on a wheel for the entire experiment. Plasma was collected before, and at 1, 2, and 4 wk postvaccination. Enzyme-linked immunosorbent assay was performed to analyze anti-OVA IgG and IgM antibodies. After 3 wk of chronic stress, all mice were injected with OVA into the ear to determine the delayed-type hypersensitivity. Results We found that chronic restraint stress significantly reduced body weight and caused adrenal hypertrophy. We also found both S-ECC and S-VWR groups had significantly elevated anti-OVA IgG (P < 0.05), whereas no significant differences between the two exercise groups. Neither S-ECC nor S-VWR altered anti-OVA IgM or delayed-type hypersensitivity responses compared with S-SED group. Conclusions Acute eccentric exercise and voluntary exercise training alleviated the chronic stress-induced anti-OVA IgG reductions in vaccination responses.

Neuromuscular Fatigue and Metabolism during High-Intensity Intermittent Exercise Purpose To examine the degree of neuromuscular fatigue development along with changes in muscle metabolism during two work-matched high-intensity intermittent exercise protocols in trained individuals. Methods In a randomized, counter-balanced, crossover design, 11 endurance-trained men performed high-intensity intermittent cycle exercise protocols matched for total work and including either multiple short-duration (18 × 5 s; SS) or long-duration (6 × 20 s; LS) sprints. Neuromuscular fatigue was determined by preexercise to postexercise changes in maximal voluntary contraction force, voluntary activation level and contractile properties of the quadriceps muscle. Metabolites and pH were measured in vastus lateralis muscle biopsies taken before and after the first and last sprint of each exercise protocol. Results Peak power output (11% ± 2% vs 16% ± 8%, P < 0.01), maximal voluntary contraction (10% ± 5% vs 25% ± 6%, P < 0.05), and peak twitch force (34% ± 5% vs 67% ± 5%, P < 0.01) declined to a lesser extent in SS than LS, whereas voluntary activation level decreased similarly in SS and LS (10% ± 2% vs 11% ± 4%). Muscle [phosphocreatine] before the last sprint was 1.5-fold lower in SS than LS (P < 0.001). Preexercise to postexercise intramuscular accumulation of lactate and H+ was twofold and threefold lower, respectively, in SS than LS (P < 0.001), whereas muscle glycogen depletion was similar in SS and LS. Rate of muscle glycolysis was similar in SS and LS during the first sprint, but twofold higher in SS than LS during the last sprint (P < 0.05). Conclusions These findings indicate that, in endurance-trained individuals, multiple long-sprints induce larger impairments in performance along with greater degrees of peripheral fatigue compared to work-matched multiple short-sprints, with these differences being possibly attributed to more extensive intramuscular accumulation of lactate/H+ and to lower rates of glycolysis during multiple long-sprint exercise.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
Crete.Greece.72100
2841026182

6948891480

alsfakia@gmail.com