Medicine and Science in Sports and Exercise最新文献

Purpose: Non-Hispanic Black (NHB) women in the United States exhibit higher prevalence and mortality rates from cardiovascular diseases compared to non-Hispanic White (NHW) women. Previous studies in NHB men have demonstrated impaired vascular function at rest and during exercise; however, to date, no studies have investigated the hyperemic responses during exercise in NHB women. Therefore, we tested the hypothesis that, compared with NHW women, NHB women would present an attenuated increase in forearm blood flow (FBF) and forearm vascular conductance (FVC) during steady-state rhythmic handgrip exercise.

Methods: FBF (duplex Doppler ultrasound) and central hemodynamics including mean arterial pressure (MAP; finger photoplethysmography) were measured in healthy young NHW (n = 16) and NHB (n = 14) women during rhythmic handgrip exercise performed at 15%, 30% and 45% of maximal voluntary contraction (MVC).

Results: FVC (calculated as FBF/MAP), FBF, and MAP were not different between groups at rest (FVC: 52 ± 13 ml/min/100 mmHg in NHW women vs. 56 ± 14 ml/min/100 mmHg in NHB women; P = 0.43). There was an intensity-dependent increase in FBF and FVC during exercise in both groups, but there was no difference between the groups (e.g., FVC at 45% MVC; NHW: 304 ± 55 ml/min/100 mmHg, NHB: 351 ± 121 ml/min/100 mmHg, interaction P = 0.257). MAP responses during exercise were also not different between groups (e.g., ΔMAP at 45% MVC; NHW: 7 ± 6 mmHg, NHB:8 ± 6 mmHg, P = 0.553). Additionally, all central hemodynamics during exercise, and flow-mediated dilation were comparable between the groups.

Conclusions: Collectively, these findings indicate that the hyperemic responses to rhythmic handgrip exercise are not different between young, healthy NHB and NHW women.

Purpose: This study characterized central and peripheral adaptations to domain-specific endurance exercise training.

Methods: Eighty-four young healthy participants were randomly assigned to age- and sex-matched groups of: continuous cycling in the 1) moderate (MOD)-, 2) lower heavy (HVY1)-, and 3) upper heavy-intensity (HVY2)- domain; interval cycling in the 4) severe-intensity domain (i.e., high-intensity interval training (HIIT), or 5) extreme-intensity domain (i.e., sprint-interval training (SIT)); or 6) control (CON). Two 3-week phases of training (three sessions per week) were performed. All training protocols, except SIT, were work-matched.

Results: Maximal oxygen uptake (V̇O2max), maximal cardiac output (Q̇max), derived maximal arterial-venous oxygen difference (a-vO2diff), blood volume (BV), plasma volume (PV), and near-infrared spectroscopy (NIRS)-derived muscle oxidative capacity (τOxCap) were measured and compared at PRE and POST. The largest change in V̇O2max occurred in HIIT (0.43 ± 0.20 L·min-1), which was greater than CON (0.02 ± 0.08 L·min-1), MOD (0.11 ± 0.19 L·min-1), HVY1 (0.24 ± 0.18 L·min-1) and SIT (0.28 ± 0.21 L·min-1) (p < 0.05) but not HVY2 (0.36 ± 0.14 L·min-1) (p > 0.05). Changes in Q̇max were observed in HVY1 (1.6 ± 0.5 L·min-1), HVY2 (3.0 ± 0.6 L·min-1), HIIT (2.9 ± 1.2 L·min-1) and SIT (1.8 ± 1.4 L·min-1) (p < 0.05) but not in MOD (1.2 ± 0.3 L·min-1) and CON (0.1 ± -0.5 L·min-1) (p > 0.05). HVY2 and HIIT produced significant changes in BV ((438 ± 101 mL, and 302 ± 38 mL) and PV (198 ± 92 mL, and 158 ± 51 mL), respectively (p < 0.05) whereas other groups did not.

Conclusions: No significant peripheral adaptations (i.e., τOxCap and a-vO2diff) were observed in any group (p > 0.05). The results indicate that higher training intensities (i.e., HVY2 and HIIT) produces larger changes in V̇O2max which is supported predominantly by central adaptations. Additionally, results suggest that, despite non-significant changes, the contribution of peripheral components to changes in V̇O2max should not be dismissed.

Purpose: to investigate whether muscle excitation during constant-work rate (WR) cycling is connected with total[Hb + Mb] and interact with oxygen uptake (V̇O2) dynamics.

Methods: Experiment 1: ten participants performed a 21-min constant-WR (CWR) within the heavy-intensity domain (i.e., 75% of the difference between the gas exchange threshold and the maximal metabolic steady state), and a ramp-to-constant-WR (rCWR) to the same WR. CWR and rCWR were repeated twice and allocated in random order. Experiment 2: nine participants performed a double-constant-WR (dCWR) consisting of a 21-min exercise bout, a short 20-sec break, and a second bout of 21 min within the heavy domain. V̇O2, EMG root mean square (EMGRMS), total[Hb + Mb] and deoxygenated hemoglobin ([HHb]) were collected from the vastus lateralis. The EMGRMS/total[Hb + Mb] and EMGRMS/[HHb] ratios were computed.

Results: The EMGRMS was lower at min 1 and 7 and total[Hb + Mb] higher at min 1 during the rCWR compared to the CWR condition (all P < 0.05). EMGRMS displayed an overshoot at min 1 which was different from min 21 during the CWR condition (P < 0.05). EMGRMS did not display an overshoot following the 20 sec break during the dCWR condition. The EMGRMS/total[Hb + Mb] inverted ratio was not different from V̇O2 (%). The EMG magnitude of frequencies ranging from ~30-to-90 Hz was initially higher and decreased over time (P < 0.05).

Conclusions: This study demonstrated that EMGRMS-derived muscle excitation can be reduced by exercise protocols that promote higher total[Hb + Mb]. Furthermore, the interaction between muscle excitation and total[Hb + Mb] matched with systemic V̇O2.

Purpose: Following anterior cruciate ligament reconstruction (ACLR), individuals present with significant and persistent deficits in surgical knee biomechanics during running. Little is known regarding the role of the hip and ankle in compensating for these knee-specific deficits. The purpose of this study was to characterize how limb (surgical and non-surgical), time post-operatively (3.5-7 months [EARLY], 8-13 months [LATE]), and running speed influence lower extremity joint-specific and total work during running post-ACLR.

Methods: Fifty-six Division I collegiate athletes post-ACLR (EARLY: n = 41, LATE: n = 42, Both: n = 27) completed running analyses at 2.68, 2.95, 3.35, 3.80 and 4.47 m/s or up to their maximum comfortable speed. Linear mixed effects models assessed the influence of limb, speed, time post-ACLR, and their interactions on hip, knee, ankle, and total negative and positive work.

Results: Surgical limb hip positive work was greater (0.044 J/kg [0.015, 0.074], p < 0.001) than the non-surgical limb EARLY. Surgical limb ankle negative (-0.054 J/kg [-0.093, -0.015], p = 0.003) and positive work (-0.115 J/kg [-0.168, -0.063], p < 0.001) were less than the non-surgical limb EARLY. Surgical limb knee negative (EARLY: -0.339 J/kg [-0.382, -0.296], p < 0.001; LATE: -0.222 J/kg [-0.265, -0.180], p < 0.001) and positive work (EARLY: -0.214 J/kg [-0.246, -0.182], p < 0.001; LATE: -0.142 J/kg [-0.174, -0.110], p < 0.001) were less than the non-surgical limb. Total negative and positive work followed the same pattern as the knee. Conclusions: Athletes post-ACLR exhibited greater hip positive work and lesser ankle positive and negative work during running of the surgical limb EARLY, that resolved LATE. Both knee and total negative and positive work of the surgical limb were substantially less than the non-surgical limb, which improved from EARLY to LATE, but between-limb asymmetries remained.

Abstract: Purpose. Blood-brain barrier (BBB) dysfunction is implicated in various neurodegenerative diseases, including Alzheimer's disease and frontotemporal dementia. Over the past decades, numerous studies have suggested that exercise can mitigate neurodegenerative processes by improving mitochondrial function. Recently, we demonstrated that exercise could reverse hippocampus-associated memory deficits and reduce BBB leakage in a modified two-kidney, one-clip (2K1C) hypertensive animal model. Based on these findings, we hypothesize that exercise restores BBB integrity in hypertensive animal models. Methods. Hypertension was induced in C57BL/6 mice via 2K1C surgery. Following three weeks of hypertension induction, mice underwent moderate-intensity treadmill exercise for five weeks. Subsequently, brain tissues were collected for immunofluorescence staining and immunoblotting analyses to assess changes in BBB structure and mitochondria-related protein expression. Results. Exercise restored hypertension-induced reductions in blood vessel density within the hippocampus. Additionally, it repaired BBB structural impairments, as evidenced by increased levels of Claudin-5 co-localization with blood vessels, enhanced perivascular astrocyte levels, and improved perivascular AQP-4 protein expression. An immunoblotting analysis revealed that exercise upregulated the PGC-1α/Nrf1/UCP-2 pathway in the 2K1C hypertensive model. However, exercise did not significantly affect Drp-1 expression. Conclusions. Exercise alleviates BBB leakage by restoring structural integrity to the BBB. These improvements may be mediated through the enhancement of mitochondrial biogenesis.

Purpose: Locomotor high-intensity interval training (HIIT) has been shown to improve walking capacity (speed and endurance) more than moderate-intensity aerobic training (MAT) after stroke, but it is unclear which training parameter(s) should be prioritized (e.g. speed, heart rate, blood lactate, step count) and to what extent walking capacity gains are the result of gait changes versus cardiorespiratory adaptations. This study aimed to assess which training parameters and longitudinal adaptations most strongly mediate 6-minute walk distance (6MWD) gains from post-stroke HIIT.

Methods: The HIT-Stroke Trial randomized 55 persons with chronic stroke and walking limitations to HIIT or MAT; each involving overground and treadmill walking, 45 minutes, 3 times/week for 12 weeks. HIIT used short maximum speed intervals, targeting >60% heart rate reserve (HRR). MAT targeted 40-60% HRR. Blinded outcomes included 6MWD, short-distance gait function (e.g. fastest 10-meter gait speed) and aerobic capacity (e.g. ventilatory threshold). This ancillary analysis used structural equation models to compare mediating effects of different training parameters and longitudinal adaptations on 6MWD changes.

Results: Net gains in 6MWD from HIIT versus MAT were primarily mediated by faster training speeds (+57 meters, p < .0001) and longitudinal gait adaptations (+37 meters, p = .0005). Training step count was also positively associated with 6MWD gains, but was lower with HIIT versus MAT, which decreased the net 6MWD gain from HIIT (-14 meters, p = .02). HIIT generated higher training heart rate and lactate than MAT, but aerobic capacity gains were similar between groups, and 6MWD changes were not associated with training heart rate, training lactate, or aerobic adaptations.

Conclusions: To increase walking capacity with post-stroke HIIT, training speed and step count appear to be the most important parameters to prioritize.

Purpose: Although physical activity (PA) has the potential to prevent iatrogenic disability, it is rarely integrated into usual care. We evaluated whether MATCH, a pragmatic unsupervised exercise intervention, could help prevent physical and functional decline in hospitalized older adults.

Methods: A quasi-randomized trial (ClinicalTrials #NCT04078334) was conducted involving 100 hospitalized patients, who were allocated to either the usual care + MATCH group (MG; n = 62) or the usual care only group (CG; n = 38). MATCH is an unsupervised PA program guided by a decision tree (3 exercises/session; 3x/day). Outcomes were assessed at admission and discharge: 1) primary outcome: functional capacities (Short Physical Performance Battery (SPPB)); 2) secondary outcomes: handgrip strength, walking speed, functional mobility (3-metre Timed-Up-and-Go (TUG)), leg muscle power (30-second chair-test), need for home care support, and functional autonomy in both instrumental and basic activities of daily living (ADL).

Results: At admission, groups were similar, except for nutritional status (p = 0.047). There were no significant differences between groups for the primary outcome (SPPB: MG:+1.5 ± 1.9 vs. CG:+1.0 ± 1.4/12pts, p = 0.25). However, the MG showed greater improvements in handgrip strength (MG:+1.7 ± 3.9 vs. CG:-0.15 ± 3.0 kg, p = 0.02) and had a lower need for home care support at discharge (MG:44.3% vs. CG:65.8%, p = 0.041). A higher proportion of MG participants improved to being at no risk of falling (TUG<14 sec), achieved good functional capacity (SPPB ≥10/12: +6.6%), increased leg muscle power (Women:<2.1/Men:<2.6(W/kgBW): -15.1%), and improved walking speed (<0.6 m/s: -30.6%) compared to the CG. Clinically meaningful improvements in ADL (+82.7%) were observed only in the MG.

Conclusions: Combining usual care with the MATCH intervention appears more effective that usual care alone in preventing physical and functional decline and reducing the need for home care support at discharge. Larger-scale efficacy studies are needed to confirm these promising results.

Purpose: Burn survivors have an increased risk for heat related illnesses, and a heightened perceptual strain during exercise (thereby impeding physical activity), both due to impaired body temperature regulation. We developed and validated a freely deployed online model that burn survivors can use to estimate their heat risk during physical activity.

Methods: Model inputs included environmental conditions, physical activity intensity and duration, body size, clothing, and burn injury size. The developed model predicts heat risk categorized as either low to moderate (change in core temperature < 1.7 °C) or high to extreme (change in core temperature ≥ 1.7 °C). We compared the core temperature responses and predicted heat risk from laboratory trials conducted in adults aged 19 to 61 years with well healed burn injuries (n = 134) or simulated burn injuries (n = 157). Burn injury sizes ranged from 20 to 80% of body surface area. Trials were conducted in our laboratory across a variety of environmental conditions (25 to 39 °C and 20 to 40 % relative humidity) and exercise intensities (46 to 357 W/m2).

Results: With heat risk as a binary outcome, the predictive accuracy of the model was 85%. The specificity of the model was 85% and the sensitivity of the model was 79%. The positive predictive value was 27% and the negative predictive value was 98%.

Conclusions: The developed model (www.bsrcalculator.org) predicts heat-risk across a variety of environmental conditions and exercise intensities. We anticipate that this tool will inform individuals of their potential risk (or lack thereof) associated with performing physical activity in the heat while also promoting a physically active lifestyle in burn survivors.

Purpose: To investigate associations between hormonal contraceptive use and physical performance, body composition, and musculoskeletal injuries in basic military training.

Methods: Female British Army recruits ( n = 450) were grouped as nonusers ( n = 182), combined oral contraceptive users (COCP; n = 184), or progestin-only users (POC; n = 144). Physical performance (2.4-km run, lift strength, leg power), body composition, iron and vitamin D status, and bone metabolism were measured at the start (week 1) and end (week 13) of training. Lower body musculoskeletal injuries were recorded from medical records.

Results: Training decreased 2.4-km run time (-3.7%) and fat mass (-9.6%), and increased lift strength (4.5%), leg power (1.5%), lean mass (5.4%), and whole-body (0.9%), arms (1.8%), and legs (1.4%) areal bone mineral density ( P ≤ 0.015); the training response was not different between groups ( P ≥ 0.173). Lift strength was lower in COCP users than nonusers ( P = 0.044). Whole-body, trunk, and leg areal bone mineral densities were lower in POC users than nonusers and/or COCP users ( P ≤ 0.041). There were no associations between hormonal contraceptive use and musculoskeletal or bone stress injury ( P ≥ 0.429). Training did not change ferritin ( P = 0.968), but decreased hemoglobin and total 25-hydroxyvitamin-D, and increased parathyroid hormone, c-telopeptide cross-links of type 1 collagen (βCTX), and procollagen type 1 N-terminal propeptide (PINP; P ≤ 0.005); the training response was not different between groups ( P ≥ 0.368). Total 25-hydroxyvitamin-D was higher, and βCTX and PINP were lower, in COCP users than nonusers and POC users; parathyroid hormone was lower in COCP users than nonusers; and βCTX and PINP were higher in POC users than nonusers ( P ≤ 0.017).

Conclusions: Hormonal contraceptive use was not associated with performance or injury outcomes in military training.

Purpose: Motion capture technology is quickly evolving, providing researchers, clinicians, and coaches with more access to biomechanics data. Markerless motion capture and inertial measurement units (IMUs) are continually developing biomechanics tools that need validation for dynamic movements before widespread use in applied settings. This study evaluated the validity of a markerless motion capture, IMU, and red, green, blue, and depth (RGBD) camera system as compared with marker-based motion capture during countermovement jumps, overhead squats, lunges, and runs with cuts.

Methods: Thirty adults were recruited for this study (sex: 18 females, 12 males; age: 25.4 ± 8.6 yrs; height: 1.71 ± 0.08 m; weight: 71.6 ± 11.5 kg). Data were collected simultaneously with four motion capture technologies (i.e., Vicon, marker-based; Theia/Optitrack, markerless; APDM Opals, IMUs; and Vald HumanTrak, RGBD camera). System validity for lower and upper body joint angles was evaluated using bias, root mean squared error (RMSE), precision, maximum absolute error, and intraclass correlation coefficients. System usability was descriptively analyzed.

Results: Overall, markerless motion capture had the highest validity (sagittal plane RMSE: 3.20°-15.66°; frontal plane RMSE: 2.12°-9.14°; transverse plane RMSE: 3.160°-56.61°), followed by the IMU system (sagittal plane RMSE: 8.11°-28.37°; frontal plane RMSE: 3.26°-16.98°; transverse plane RMSE: 5.08°-116.75°), and lastly the RGBD system (sagittal plane bias: 0.55°-129.48°; frontal plane bias: 1.35°-52.06°).

Conclusions: Markerless motion capture and IMUs have moderate validity for joint kinematics, whereas the RGBD system did not have adequate validity. Markerless systems have lower data processing time, require moderate technical expertise, but have high data storage size. IMUs are easier to use, can collect data in any location, but require participant set-up. Overall, individuals using motion capture should consider the specific movements, testing locations, and technical expertise available before selecting a system.