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 with 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 -1 ·100 mm Hg -1 in NHW women vs 56 ± 14 mL·min -1 ·100 mm Hg -1 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 -1 ·100 mm Hg -1 , NHB: 351 ± 121 mL·min -1 ·100 mm Hg -1 , interaction P = 0.257). MAP responses during exercise were also not different between groups (e.g., ΔMAP at 45% MVC; NHW: 7 ± 6 mm Hg, NHB:8 ± 6 mm Hg, P = 0.553). In addition, 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 aimed to examine central and peripheral physiological adaptations contributing to increases in maximal oxygen uptake (V̇O 2max ) following a 12-wk vigorous endurance exercise program in healthy, older and young adults.

Methods: Fourteen participants (7 older: 68 ± 7 yr and 7 young: 26 ± 7 yr; 9 males and 5 females) engaged in a cycling training program three times a week for 45 min at ~70%V̇O 2max . Changes in V̇O 2max , cardiac function, V̇O 2 extraction, muscle capillarization, and mitochondrial content from pre- to post-training were examined.

Results: The increase in V̇O 2max from pre- to post-training for all participants (20% ± 8%) was accompanied by increases in maximal cardiac output (Q˙ max ; 15% ± 11%), maximal stroke volume (SVmax; 14% ± 12%), muscle fiber cross-sectional area (CSA; 17% ± 21%) and perimeter (P; 7% ± 9%), citrate synthase (CS) activity (144% ± 175%), individual capillary-to-fiber ratio (C:Fi; 32% ± 17%), capillary-to-fiber perimeter exchange index (CPFE: 30% ± 15%), capillary contact (CC; 38% ± 20%), capillary density (CD; 22% ± 17%), and arteriovenous O 2 difference (a-vO 2 diff; 4% ± 6%) ( P < 0.05 for all). No training-related variation existed for maximal heart rate (HRmax; -1% ± 4%; P = 0.448). Changes in V̇O 2max were positively correlated with Q˙ max ( r = 0.830: P < 0.001), SVmax ( r = 0.655; P = 0.011), CD ( r = 0.546; P = 0.043), and CS activity ( r = 0.630; P = 0.021). No significant correlations were found for changes in V̇O 2max and changes in HRmax, a-vO 2 diff, muscle fiber CSA and P, CC, C:Fi, and CPFE ( P > 0.05 for all).

Conclusions: Cardiorespiratory fitness improvements were primarily determined by enhancement in central (i.e., cardiac function) and peripheral (i.e., vascularization) adaptations within the V̇O 2 transport system as well as the upregulation of mitochondrial aerobic enzymatic activity (i.e., CS activity) at the intracellular level.

Introduction/purpose: Females have lower physical activity (PA) levels and inferior outcomes compared with males following formal rehabilitation after anterior cruciate ligament (ACL) reconstruction. This observational study aimed to determine if PA levels and sedentary behavior change and vary by sex during the time before and 6 months after ACL reconstruction.

Methods: PA and sedentary behavior were measured in an observational cohort of 30 participants (19.6 ± 4.9 yr old, 66.7% female) using a three-axis accelerometer before (preoperative) and at 2, 4, and 6 months after ACL reconstruction. Daily steps, daily minutes of moderate to vigorous PA (MVPA), and percentage of wake time in sedentary behavior (%SED) were measured. Two-by-four (sex-time) repeated measures analyses of variance were used to test changes in PA and %SED.

Results: In females and males, daily steps and MVPA increased from 2 to 4 months after ACL reconstruction (all P < 0.05) but not between other consecutive time points. %SED did not change between any consecutive time points. At 6 months, females walked fewer daily steps ( P = 0.002; females: 7003 ± 2068; males: 10,406 ± 3277), spent fewer minutes in MVPA ( P = 0.010; females: 31.3 ± 14.6; males: 54.9 ± 32.4), and spent more time in %SED ( P = 0.003; females: 67.9 ± 7.4; males: 57.5 ± 9.5).

Conclusions: PA levels increased in females and males from 2 to 4 months after ACL reconstruction but not between other consecutive time points from before through 6 months after surgery. Females completed less PA and spent more time in sedentary behavior than males and may require greater monitoring to improve PA after ACL reconstruction. The disparity in PA and sedentary behavior across sex follows consistent previous findings that outcomes after ACL reconstruction are poorer in females compared with males.

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-intensity (MOD), 2) lower heavy-intensity (HVY1), and 3) upper heavy-intensity (HVY2) domain; interval cycling in the 4) severe-intensity domain (i.e., high-intensity interval training (HIIT), and 5) extreme-intensity domain (i.e., sprint-interval training (SIT)); or 6) control (CON). Two 3-wk phases of training (three sessions per week) were performed. All training protocols, except SIT, were work matched.

Results: Maximal oxygen uptake (V̇O 2max ), maximal cardiac output (Q˙ max ), derived maximal arterial-venous oxygen difference (a-vO 2diff ), 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 V̇O 2max 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 Q˙ max 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 and 302 ± 38 mL) and PV (198 ± 92 and 158 ± 51 mL), respectively ( P < 0.05), whereas other groups did not.

Conclusions: No significant peripheral adaptations (i.e., τOxCap and a-vO 2diff ) were observed in any group ( P > 0.05). The results indicate that higher training intensities (i.e., HVY2 and HIIT) produce larger changes in V̇O 2max , which is supported predominantly by central adaptations. In addition, results suggest that, despite nonsignificant changes, the contribution of peripheral components to changes in V̇O 2max should not be dismissed.

Purpose: This study compared the physiological effects of a moderate-intensity interval training (MIT) microcycle followed by an active recovery period (collectively termed MIT block ) with a time-matched regular training period (REG) during the general preparation phase in well-trained cyclists.

Methods: Using a randomized crossover design, 30 well-trained male cyclists (maximal oxygen consumption (V̇O 2max ), 70.5 (4.6) mL·min -1 ·kg -1 ) completed both MIT block and REG. The MIT microcycle involved six interval sessions over 7 d with 5-7 × 10-14-min work intervals at a rating of perceived exertion (RPE) of 14-15 on the Borg 6-20 scale. A 6-d active recovery period followed before physiological testing. During REG, cyclists performed their regular preparatory-phase training routine, which primarily involved low-intensity exercise. Specific guidelines included completing either two MIT sessions or one MIT session and one high-intensity interval session per week. Endurance performance indicators assessed included changes in 15-min maximal average power output (PO 15min ), power output at 4 mmol·L -1 [blood lactate] (PO 4mmol ), 1-min peak power output during incremental testing (PO V̇O2max ), and V̇O 2max .

Results: Although the Training Impulse (TRIMP) score was not different between MIT block and REG (1944 (436) vs 1800 (232), respectively; P = 0.27), MIT block resulted in significantly greater improvements than REG in PO 4mmol (4.0% (4.4%) vs -1.3% (3.7%), P < 0.01), PO V̇O2max (2.5% (4.5%) vs -0.7% (3.9%), P < 0.01), and V̇O 2max (2.0% (3.9%) vs 0.0% (3.5%), P = 0.05). Changes in PO 15min were not statistically different between MIT block and REG (3.9% (8.3%) vs 0.2% (6.8%), P = 0.14). During MIT intervals, rating of perceived exertion was 14.4 (0.3), corresponding to 66% (5%) of PO V̇O2max , 85% (3%) of maximal heart rate, and 2.8 (1.1) mmol·L -1 [blood lactate].

Conclusions: Six moderate-intensity interval sessions over 7 d, followed by a 6-d active recovery period, induce improvements in endurance performance indicators compared with a time-matched regular training period in well-trained cyclists.

Purpose: Many elite road-race cyclists have low areal bone mineral density (aBMD) as previously shown by dual-energy x-ray absorptiometry (DXA). However, aBMD provides limited insight into bone quality. Therefore, this cross-sectional study aimed to assess volumetric BMD (vBMD), bone microarchitecture, and bone strength in elite road-race cyclists using high-resolution peripheral computed tomography (HR-pQCT), along with aBMD measured by DXA.

Methods: Twenty female elite (Tier 3/4) road-race cyclists (21 ± 2 yr; body mass index, 20.8 ± 1.6 kg·m -2 ) had DXA scans at the hip, lumbar spine, and total body to assess aBMD, and HR-pQCT scans at the distal radius and tibia to assess vBMD, bone microarchitecture, and failure load. Z -scores were calculated for all outcomes, with Z -scores <-1 considered as low or impaired. The risk of low energy availability was assessed using the Low Energy Availability in Females Questionnaire.

Results: Low aBMD was observed in 20%, 25%, 35%, and 10% of the participants at the hip, femoral neck, lumbar spine, and total body, respectively. Low total vBMD was present in 45% and 40% at the distal radius and tibia, respectively. With regard to bone microarchitecture, the tibial cortical area and tibial cortical thickness were low in 40% and 60% of the participants, respectively, and number and thickness of trabeculae at the tibia were low in 40% and 30% of the participants. The impairments were less pronounced at the distal radius. Failure load was low in 15% (radius) and 20% (tibia) of the participants.

Conclusions: Along with low aBMD, a substantial proportion of female elite cyclists had impaired bone microarchitecture, mainly characterized by a low cortical area and thickness and low trabecular number and thickness, especially at the distal tibia.

Purpose: The aim of this study is to propose muscular strength normative data tables for the cancer population and observe the effects of exercise training on categorical placement.

Methods: Data from cancer survivors ( n = 659) encompassing various cancer types across all cancer stages were used for this study. Participants completed assessments to estimate one-repetition maximum (1RM) for both chest press and leg press, in addition to a test of maximum effort dominant handgrip strength. Strength-to-weight ratio (SWR) and handgrip strength values were divided into categories by sex and age and compared with normative values from the apparently healthy population as reported by the American College of Sports Medicine.

Results: Comparison of mean SWR and handgrip strength values for the cancer population to the apparently healthy normative data resulted in each age/sex group being classified as "average" or lower. Of the 30 age/sex classification groups for the cancer population, 23 demonstrated mean strength values in the lowest category of their respective assessment.

Conclusions: Normative data derived from the apparently healthy population may not be an appropriate comparison for the cancer population and may not be sensitive enough to detect categorical improvements in muscular strength resulting from exercise training. We provide an initial data set that could serve as a first step in the development of normative strength data for this population.

Purpose: This study aimed to investigate whether muscle excitation during constant-work rate (WR) cycling is connected with total[Hb + Mb] and whether they interact with the oxygen uptake (V̇O 2 ) dynamics.

Methods: In experiment 1, 10 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. In experiment 2, nine participants performed a double-constant-WR (dCWR) consisting of a 21-min exercise bout, a short 20-s break, and a second bout of 21 min within the heavy domain. V̇O 2 , EMG root-mean-square (EMG RMS ), total[Hb + Mb], and deoxygenated hemoglobin ([HHb]) were collected from the vastus lateralis. The EMG RMS /total[Hb + Mb] and the EMG RMS /[HHb] ratios were computed.

Results: The EMG RMS was lower at minutes 1 and 7 and total[Hb + Mb] higher at minute 1 during the rCWR compared with the CWR condition (all P < 0.05). EMG RMS displayed an overshoot at minute 1, which was different from minute 21 during the CWR condition ( P < 0.05). EMG RMS did not display an overshoot after the 20-s break during the dCWR condition. The EMG RMS /total[Hb + Mb] inverted ratio was not different from V̇O 2 (%). 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 EMG RMS -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 V̇O 2 .

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. After 3 wk of hypertension induction, mice underwent moderate-intensity treadmill exercise for 5 wk. 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 colocalization 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: The aim of the study was to describe trends, characteristics, and mortality associations of U.S. adults unable to do aerobic leisure-time physical activity (LTPA) from 1998 to 2018.

Methods: We used data from 21 U.S. National Health Interview Survey annual updates. Logistic binary regressions were used to estimate odds ratios (OR) and Cox proportional regression models to estimate hazard ratios (HR). People unable to do aerobic LTPA was self-reported.

Results: From a total of 621,499 participants pooled, 10,554 (1.70%) were unable to do PA. Adults who were older than 65 yr (OR = 14.37, 95% confidence interval [CI] = 12.69-16.28), unemployed (OR = 15.61, 95% CI = 14.20-17.17), reported a bad self-rated health (OR = 45.69, 95% CI = 39.52-52.83), and had limitations with instrumental activities of the daily living (OR = 16.51, 95% CI = 15.68-17.38) had a higher risk of being unable to do aerobic LTPA. During a mean follow-up time of 10.36 yr, 5137 participants (50.44%) who were unable to do aerobic LTPA died. They had a higher mortality risk for all-cause (HR = 1.23, 95% CI = 1.18-1.28) mortality compared with the participants who were able to do aerobic LTPA. Adults unable to do aerobic LTPA had an increased risk of all-cause mortality (HR = 1.13, 95% CI = 1.09-1.19) than those who were able but did not perform aerobic LTPA.

Conclusions: U.S. adults unable to perform aerobic LTPA showed a higher risk of all-cause mortality compared with adults who were able to perform aerobic LTPA, and even compared with those who were physically inactive.