Medicine and Science in Sports and Exercise最新文献

Purpose: Doxorubicin (DOX) is a potent chemotherapeutic agent whose clinical use is limited due to cardiorespiratory muscle toxicity. The objective of this study was to evaluate sex differences in the severity of DOX myotoxicity and to determine the effectiveness of preconditioning exercise to confer protection.

Methods: Adult male and female Sprague-Dawley rats remained sedentary (Sed) or performed 2 wk of exercise preconditioning (5 d·wk -1 , 60 min·d -1 , 30 m·min -1 ) (Ex). Twenty-four hours after the final exercise bout, rats received saline (Sal) or DOX (20 mg·kg -1 IP). Forty-eight hours later, cardiac and respiratory muscle functions were assessed and tissues were collected.

Results: Exercise preconditioning increased exercise tolerance in both male and female Sal- and DOX-treated rats compared with their Sed counterpart (male: Sed-DOX = 26.89 ± 2.30 min vs Ex-DOX = 39.01 ± 2.76 min; female: Sed-DOX = 24.65 ± 1 .81 min vs Ex-DOX = 45.14 ± 3.72 min). DOX reduced left ventricle fractional shortening (FS%) and maximal diaphragm muscle force production compared with Sal-treated rats in males and females, which were only prevented with exercise in female DOX-treated rats (FS% male: Sed-DOX = 35.57 ± 1.59% vs Ex-DOX = 35.12 ± 0.67%; female: Sed-DOX = 36.84 ± 1.11% vs Ex-DOX = 43.99 ± 2.56% and force male: Sed-DOX = 17.93 ± 1.13 N·cm -2 vs Ex-DOX = 20.91 ± 1.01 N·cm -2 ; female: Sed-DOX = 19.71 ± 0.68 N·cm -2 vs Ex-DOX = 22.00 ± 1.47 N·cm -2 ). These effects were associated with sex-specific differences in circulating hormones, muscle DOX accumulation, and gene expression.Conclusions: Cardiorespiratory muscle toxicity occurred after acute DOX exposure in male and female rats. Although, exercise preconditioning elicited a robust increase in cardiorespiratory endurance in both sexes, the beneficial effects of exercise on cardiac and diaphragm muscle function occurred exclusively in female rats.

Introduction: Running economy (RE) deteriorates during prolonged running (i.e., RE durability), although it is unknown if runners' training characteristics influence RE durability. Furthermore, the extent of the decrement in neuromuscular capabilities after running could also contribute to differences in RE durability. Therefore, this study aimed to compare RE durability during a 90-min run and the decrements in neuromuscular capabilities, between athletes who did or did not practice regular long runs, while pair-matched for performance status.

Methods: Two groups of 13 male runners were recruited as long (LDT; regular long runs ≥90 min) or short distance training runners (SDT; all runs <70 min) and matched for 10-km performance (39:10 vs 39:00 min:s; maximal oxygen uptake 56.6 vs 58.9 mL·kg -1 ·min -1 ). Participants completed preliminary assessments to determine lactate threshold and maximal oxygen uptake, and then on a separate occasion, a 90-min run at lactate threshold. Respiratory gases were collected every 15 min, and isometric squat peak force and countermovement jump were assessed before and after the run.

Results: Changes in RE occurred earlier and were larger for SDT than LDT, reaching +6.0% versus +3.1% at 90 min, respectively ( P < 0.001). Isometric squat force (-19.4% vs -12.2%; P = 0.002) and countermovement jump mean power (-6.6% vs +2.2%; P = 0.011) decreased more in SDT than LDT runners; however, these changes were not correlated with RE durability, whereas correlations were found between RE durability and the weekly longest run ( r = -0.67; P < 0.001) and training volume ( r = -0.48; P = 0.038).

Conclusions: This study is the first to demonstrate that the presence of long runs and higher training volumes positively affects RE durability and decrements in neuromuscular capability in performance-matched runners. These results provide important insights into how training characteristics may help explain differences in durability, although intervention studies are needed to confirm these cross-sectional findings.

Purpose: Aberrant lower limb biomechanics of young females contribute to elevated knee loads and a susceptibility to non-contact anterior cruciate ligament (ACL) injury. Specific design features of athletic footwear may alter impact-related loads transferred up the kinetic chain to the knee. This cross-sectional biomechanical study examined the effects of modifiable footwear design features (heel height/pitch and medial arch support) on ACL force-time parameters of females during single-limb landing.

Methods: Fifty-two healthy late/post-pubertal females (Tanner stage IV-V) performed a single-limb drop-lateral-jump (DLJ) task in nine footwear conditions, with different combinations of shoe pitch (4 mm, 7 mm and 10 mm) and medial arch support (no support, low support and high support). Using three-dimensional joint kinematics, ground-reaction forces, and electromyography (EMG) data, an EMG-informed neuromusculoskeletal computational model predicted ACL force during the weight-acceptance phase of the DLJ task. A mixed effects linear regression model was used to compare the magnitude and temporal characteristics of ACL force between footwear conditions. Tukey's post-hoc comparisons were conducted for significant (p<0.05) main effects or interactions.

Results: For peak ACL force, no significant main effect or interaction was found. A significant main effect of shoe pitch was found for time-to-peak ACL force (p<0.001), where the 4mm shoe pitch delayed time-to-peak by 3.23ms and 4.28ms compared to the 7mm (p<0.001) and 10mm (p<0.001) conditions, respectively.

Conclusion: Although a delayed time-to-peak ACL force was observed with the 4mm shoe pitch condition, the relatively small temporal differences observed, and the fact that peak ACL force did not differ across pitch variants, suggest that these findings may have few real-world implications.

Purpose: Running economy (RE) improvements in advanced footwear technologies (AFTs) have been investigated during short running bouts, whereas performance-enhancing effects may be greater over longer distances. Therefore, the aim was to compare RE and biomechanics during a 90-min run between AFTs and traditional shoes in highly trained distance runners.

Methods: Nine highly trained distance runners (five females) visited our laboratory on two separate sessions within 14 d. In each session, they performed a submaximal threshold assessment treadmill test, followed by a 90-min treadmill run. We used linear mixed effects models (with random intercepts for participants) to examine the effects of time, shoe condition, and their interaction on energetic cost of transport (ECOT) and biomechanical measures.

Results: Participants (age: 32.4 ± 8.4 yr, body mass index: 20.8 ± 1.2 kg·m -2 ) had a mean maximal World Athletics score of 930 ± 84 points, corresponding to 10 km times (min:s) of 30:17 and 36:09 for males and females. ECOT was different between AFT and non-AFT ( β = 0.57 (0.41-0.72), P = 0.009) throughout 15 to 90 min. On average, ECOT was 3.18% (95% confidence interval, 2.14-4.22) lower in the AFTs compared with the non-AFT condition. Over time, ECOT ( β = 0.30 (0.19-0.41), P < 0.001) increased by 5.63% (95% confidence interval, 3.00-8.27) across both shoe conditions, but was not shoe-dependent (ECOT: P = 0.553). With AFTs, step rate was lower ( β = 0.13 (0.04 to 0.21), P = 0.030), flight time longer ( β = -0.08 (-0.14 to -0.03), P < 0.001), and contact time ( β = 0.05 (-0.00 to 0.11), P = 0.001) shorter than with non-AFTs, but differences disappeared over time.

Conclusions: There were no differences between shoe conditions in deterioration of RE during the 90-min run, but AFTs maintained their beneficial properties in RE over time and therefore are probably a good choice for long distances.

Background: Transitioning to retirement may change physical activity, sedentary behavior, and sleep, i.e., 24-h movement behaviors, but it is unknown whether these changes are linked to cognitive function. This study investigates the longitudinal associations between changes in 24-h movement behaviors and cognitive function during the retirement transition.

Methods: Study population consisted of public sector workers ( n = 146; mean age, 63.3 yr; SD, 1.0) from the Finnish Retirement and Aging study. A thigh-worn Axivity accelerometer was used to estimate daily time in sleep, sedentary behavior (SED), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA) before and after retirement (1 yr in between). Similarly, computerized Cambridge Neuropsychological Test Automated Battery was conducted repeatedly to evaluate six cognitive domains: learning and memory, working memory, sustained attention and information processing, executive function and cognitive flexibility, and reaction time. Associations between changes in 24-h movement behaviors and cognitive function were analyzed using compositional linear regression and isotemporal substitution analyses.

Results: An increase in active (LPA and MVPA) relative to passive behaviors (sleep and SED) and SED relative to sleep were associated with improvement in reaction time (β ilr = 0.21, P = 0.04, β ilr = 0.55, P = 0.02). Especially reallocating time from sleep to other behaviors showed positive associations. For instance, reallocating 30 min from sleep to other behaviors was associated with 0.05 standardized unit improvement in reaction time. No associations between changes in movement behaviors and changes in any other cognitive domain were observed.

Conclusions: Reallocating time from sleep to other behaviors during retirement transition was associated with improvement in reaction time. Further studies are needed to examine long-term consequences of changes in 24-h movement behaviors for cognitive function.

Introduction: Sprint performance is a priority for coaches and athletes. Several kinematic variables, including horizontal touchdown distance (HTD) and inter-knee touchdown distance (IKTD), are targeted by coaches to increase top sprinting speed. However, the results of past research are conflicting, potentially due to the use of experimental inter-athlete study designs where it is not possible to establish cause-effect relationships.

Methods: In this study, we used a predictive simulation approach to assess cause-effect relationships between HTD and IKTD and sprinting speed. We scaled a three-dimensional musculoskeletal model to match the anthropometry of an international caliber male sprinter and generated predictive simulations of a single symmetric step of top-speed sprinting using a direct collocation optimal control framework. We first used our simulation framework to establish the model's top speed with minimal constraints on touchdown kinematics (the optimal simulation). Then, in additional simulations, we enforced specific HTD or IKTD values (±2, 4, and 6 cm compared with optimal).

Results: The model achieved a top speed of 11.85 m·s -1 in the optimal simulation. Shortening HTD by 6 cm reduced speed by 7.3%, whereas lengthening HTD by 6 cm had a smaller impact on speed, with a 1.6% reduction. Speed in the simulation was insensitive to the IKTD changes we tested.

Conclusions: The results of our simulations indicate that there is an optimal HTD to maximize sprinting speed, providing support for coaches and athletes to adjust this technique variable. Conversely, our results do not provide evidence to support utilizing IKTD as a key technique variable for speed enhancement. We share the simulation framework so researchers can explore the effects of additional modifications on sprinting performance ( https://github.com/nicos1993/Pred_Sim_Sprinting ).

Abstract: This Consensus statement provides an update to the 1996 American College of Sports Medicine Position Stand: The Use of Blood Doping as an Ergogenic Aid. Red blood cell (RBC) mass directly influences exercise performance because RBCs are critical to the transport of oxygen to skeletal muscle, as well as their role in maintaining acid-base status and regulating blood flow. Blood doping is defined as the practice of artificially increasing RBC volume for the purpose of improving exercise performance. Blood doping methods have classically included reinfusion of stored blood as well as administration of pharmaceutical agents such as recombinant human erythropoietin, hypoxia-inducible factor stabilizers or nonpharmaceutical substances, like cobalt or xenon, which stimulate the erythropoietic pathway. It is clear through scientific consensus that other methods to naturally increase hemoglobin, such as hypoxic or hyperoxic exposure, are not considered blood doping. More recently, emerging blood doping threats through gene manipulation have received new attention. In the last 25 yr, the science and technology surrounding oxygen sensing and erythropoiesis, pharmacological intervention, and doping detection has advanced substantially, dictating this updated review. It is the position of the American College of Sports Medicine that any blood doping procedure used with the actual or potential to improve athletic performance is unethical and unfair and exposes the athlete to unwarranted and potentially serious health risks.

Background: Few studies have examined the longitudinal associations of accelerometer-based measures of sedentary and physical activity behaviors with subclinical heart failure (HF) in midlife. This is a key gap given an improved understanding of modifiable factors associated with HF risk may better inform prevention strategies. We hypothesize that more time in light intensity physical activity (LIPA) and/or moderate or vigorous intensity physical activity (MVPA) and less sedentary time will be related to lower levels of HF biomarkers [N-terminal pro B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hscTnT)] across midlife.

Methods: Data are from 2,494 Coronary Artery Risk Development in Young Adults (CARDIA) participants without clinical HF [58.9% women, 45.7% Black persons, mean (± SD) aged 51.1 ± 7.2 years at the baseline contributing exam] with at least one occurrence of concurrent valid accelerometer (ActiGraph 7164/GT3X; Ametris; Pensacola, FL) wear and HF biomarkers at the CARDIA Year 20, 30 and/or Year 35 follow-up examinations. Adjusted linear mixed effects models were used to estimate the associations. Heterogeneity in the associations by the four race-sex groups represented in CARDIA was also examined.

Results: In the fully adjusted models, every 5-minute higher MVPA was associated with -0.05 (95% CI: -0.09 to -0.01, p = 0.022) lower hscTnT. The associations of sedentary and LIPA with hscTnT and associations of any accelerometer estimate with NT-proBNP were not statistically supported (all p>0.05). Findings were similar when clinically relevant categories of HF biomarker outcomes were used in the analysis.

Conclusions: Findings address research gaps in the literature and demonstrate the importance of MVPA during the midlife transition for HF prevention before the onset of overt signs or symptoms.

Purpose: Although most patients recover well from COVID-19 infection, this may not be the case of those who experienced severe dysfunction after being admitted to intensive care unit (ICU). This study aimed to assess the recovery of patients who experienced severe multiple dysfunctions after being admitted to ICU for COVID-19 infection.

Methods: Forty-seven patients hospitalized and mechanically ventilated in ICU for SARS-CoV-2 infection underwent evaluations at 4 to 8 wk (T1) and 6 months (T2) post-ICU discharge. Evaluations included questionnaires, lung function tests, incremental cardiopulmonary exercise testing, and neuromuscular function tests.

Results: From T1 to T2, the percentage of patients classified as fatigued decreased from 56% to 21% whereas forced vital capacity and the forced expiratory volume in 1 s increased by 13% and 8% ( P < 0.05) to reach 93% and 95% of predicted values at T2, respectively. Peak work rate also increased from 97 to 135 W (+35 ± 32%, P < 0.001). Likewise, V̇O 2peak increased from 18.3 to 21.6 mL·min -1 ·kg -1 (+18 ± 27%, P < 0.001) to reach 72% of predicted values. Maximal strength and the number of contractions during the fatigability test increased between T1 and T2 by 41% and 39%, respectively (both P < 0.001).

Conclusions: Six months of recovery improved patients' physical function and reduced fatigue.

Purpose: We aimed to investigate whether the addition of carbohydrates (sucrose [Suc] or isomaltulose [Iso]) to a beverage containing glycerol (Gly) and sodium (Na) would enhance fluid balance, thermoregulatory response, and high-intensity exercise capacity during exercise in hot environments.

Methods: In a randomized, double-blinded, and crossover study, 13 healthy men consumed 1 L of beverage containing 1) 7% Gly + 0.5% Na (Gly + Na), 2) Gly + Na with 7% Suc (Gly + Na + Suc), 3) Gly + Na with 7% Iso (Gly + Na + Iso), or 4) water (CON) over 40 min in a hot environment (32°C, 50% relative humidity). Participants then completed three 30-min cycling bouts at 50% peak oxygen consumption (V̇O 2peak ), followed by a time-to-exhaustion (TTE) trial at 80% V̇O 2peak . Fluid balance and thermoregulatory response were assessed throughout the experiment.

Results: Compared with CON, beverages containing Gly and Na attenuated the total urine volume (all P < 0.001), and the addition of Iso (331 ± 84 g) further encouraged this response compared with Gly + Na and Gly + Na + Suc (429 ± 68 and 445 ± 133 g, respectively, both P ≤ 0.030). Compared with CON, the plasma volume increased with Gly + Na + Suc during the first exercise bout (-2.2% ± 6.7% and 4.3% ± 5.4%, respectively, P = 0.048) and with Gly + Na + Iso during the TTE (-9.1% ± 4.4% and -4.1% ± 4.0%, respectively, P = 0.025). The rectal temperature increased whereas local sweating responses were reduced more with Gly- and Na-containing beverages than with CON (all P ≤ 0.028). No differences were found in TTE among the beverages ( P = 0.159).

Conclusions: Adding Suc or Iso to Gly- and Na-contained beverages partially improves fluid balance but does not improve thermoregulatory responses and performance during moderate-intensity exercise in hot environments.