Medicine and Science in Sports and Exercise

• Physical Activity and Sedentary Behavior Differ by Sex during the First 6 Months after Anterior Cruciate Ligament Reconstruction

  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

• Influence of Running Speed and Time Postoperatively on Lower Extremity Work in Collegiate Athletes after Anterior Cruciate Ligament Reconstruction

  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 nonsurgical), time postoperatively (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−1 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 work and positive work. Results Surgical limb hip positive work was greater (0.044 J·kg−1 [95% CI = 0.015–0.074], P

• Achilles Subtendons Stiffness Differ in People with and without Achilles Tendinopathy

  Purpose Previous work showed altered mechanical properties of the Achilles tendon in the presence of tendinopathy, considering the Achilles tendon as a homogeneous structure with the gastrocnemius medialis (GM) subtendon representative of it. However, the Achilles tendon consists of three semi-independent structures: the GM, gastrocnemius lateralis (GL), and soleus (SOL) subtendons, each independently pulled by their respective muscle. The aim of this study was (i) to compare the mechanical properties of the different Achilles subtendons in humans in vivo by considering the force of each muscle within the triceps surae group and (ii) to determine whether the loss of stiffness in the presence of tendinopathy is specific to individual subtendons. We hypothesized that (i) stiffness would differ between subtendons in healthy participants and that (ii) the loss of stiffness in people with Achilles tendinopathy compared with healthy controls would not affect the three subtendons identically. Methods Fourteen participants with tendinopathy and 14 controls performed ramped isometric plantarflexions. Simultaneously, the elongation of the three subtendons was recorded, and an estimate of the force pulling on each was made (from muscle activation and volume). Stiffness was calculated from the individual muscle index of force–subtendon elongation relationships. Results Results showed that regardless of the group, SOL stiffness was significantly higher than stiffness of both gastrocnemii (muscle effect: P 0.925, d = 0.3). Conclusions This study supports the hypothesis that the biomechanical properties of the Achilles tendon differ between subtendons and further shows that the loss of stiffness in Achilles tendinopathy is specific to the GL subtendon.

• Maternal Physical Activity, Fitness, and Body Composition in Women with Gestational Diabetes: A Prospective Study

  Purpose This study aimed to 1) describe perinatal changes in physical activity (PA), physical fitness (PF), and body composition (BC) and 2) investigate prospective associations between PA and PF, and between PF and BC in metabolically high-risk women with gestational diabetes mellitus (GDM). Methods This secondary analysis of the MySweetheart trial included 211 women with GDM. Outcomes were measured at 24 to 32 wk of gestational age (GA) and at 1 yr postpartum. Physical activity was measured using accelerometer and BC with bioelectrical impedance analysis (fat mass [FM], fat-free mass [FFM]) or dual-energy X-ray absorptiometry (FM, visceral adipose tissue [VAT], lean mass [LM]; postpartum only). Regarding PF, handgrip strength and cardiorespiratory fitness (CRF) were assessed, the latter using the Chester step test to estimate the maximal oxygen uptake (V̇O2max). Models were adjusted for sociodemographic variables and BMI where applicable. Results Between pregnancy and the postpartum, sedentary time decreased (P

• Exercise Rescues Blood–Brain Barrier Structural Impairment and Enhances Mitochondrial Biogenesis in a Hypertensive Mouse Model

  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.

• Changes in V̇O2max after 6 wk of Intensity Domain-Specific Training: Role of Central and Peripheral Adaptations

  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 (V̇O2max), maximal cardiac output (Q˙max), 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). 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). 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). The results indicate that higher training intensities (i.e., HVY2 and HIIT) produce larger changes in V̇O2max, which is supported predominantly by central adaptations. In addition, results suggest that, despite nonsignificant changes, the contribution of peripheral components to changes in V̇O2max should not be dismissed.

• Peripheral and Central Hemodynamic Responses to Rhythmic Handgrip Exercise in Young, Healthy Black Women

  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.

• Oxygen Uptake Dynamics Conform to Acute Changes in Muscle Excitation and Total Hemoglobin Concentration during Constant Work Rate Exercise

  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 (V̇O2) 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. 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 the EMGRMS/[HHb] ratios were computed. Results The EMGRMS 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

• Trends, Characteristics, and Mortality of U.S. Adults Unable to Do Aerobic Leisure-Time Physical Activity: The U.S. National Health Interview Survey 1998–2018

  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.

• Cardiometabolic Benefit of Replacing Sedentary Time with Light-Intensity Physical Activity: Compositional Data Analysis of the Nijmegen Exercise Study

  Purpose The cardiometabolic benefits of replacing sedentary time with light-intensity physical activity (LIPA) are unclear. We studied the associations of hypothetically reallocating sedentary time toward LIPA with changes in cardiometabolic risk factors using thigh-worn accelerometery. We also explored whether reallocation effects differed across subgroups with low, moderate, and high sedentary time and compared proportionally similar reallocations to either LIPA or moderate-to-vigorous physical activity. Methods We assessed physical behaviors across 8 consecutive days using thigh-worn accelerometers among adults from the Nijmegen Exercise Study. Multiple cardiometabolic risk factors were assessed and categorized as 1) anthropometrics, 2) cardiovascular biomarkers, and 3) glucose metabolism. Reallocation effects were estimated for each cardiometabolic risk factor using compositional isotemporal substitution models adjusted for confounders. Analyses were repeated in sedentary time subgroups, that is, 10 h·d−1. Results We included 1041 participants (64 (standard deviation 11) yrs; 39.5% female). Reallocating sedentary time toward LIPA was associated with improvements in anthropometrics, some cardiovascular biomarkers, and glucose metabolism; for example, replacing 60 min·d−1 of sedentary time with LIPA was associated with improvements in body mass index (−0.28 (−0.42 to −0.13) kg·m−2), estimated glomerular filtration rate (0.68 (0.15 to 1.20) mL·min−1·1.73m−2), and glucose (−0.05 (−0.08 to −0.03) mmol·L−1). Trends suggested that reallocation benefits were strongest in those with >8.5 h·d−1 of sedentary time. Proportionally similar replacements of sedentary time with either LIPA or moderate-to-vigorous physical activity were associated with similar cardiometabolic benefits. Conclusions Reallocation of sedentary time to LIPA was associated with improvements in cardiometabolic risk factors, predominantly in anthropometrics and glucose metabolism, with greater benefits in the most sedentary individuals. Time reallocation from sedentary time to LIPA may be an effective and arguably feasible strategy to improve population-wide cardiometabolic health.

• BEETter AGING: Short-Term Dietary Nitrate Supplementation Enhances Muscle Contractile Properties in Older But Not in Young Adults

  Purpose Dietary nitrate (NO3−) supplementation has been shown to improve skeletal muscle contractile function and reduce fatigue, potentially due to alterations in skeletal muscle Ca2+ handling/sensitivity. Because aging muscle can have impaired Ca2+ handling, the aim of the study was to evaluate the effects of dietary NO3− supplementation on muscle contractile properties in young and older adults. Methods Eleven older (69 ± 4 yr, O) and 11 young (26 ± 2 yr, YG) adults consumed either NO3−-rich beetroot juice (BR) or placebo (PLA), for 7 d. After supplementations, plantar flexors of dominant leg were evaluated as follow: a) maximal voluntary isometric contraction (MVIC), b) potentiated single twitches (Twpot) and double twitches electrical stimulations at the frequency of 100 Hz (Db100) on the tibial posterior nerve, c) a fatigue isometric (70% of MVIC) test until exhaustion. The force–frequency relationship was assessed with trains of electrical pulses across a wide range of frequencies on the muscle belly of the nondominant leg. Results BR supplementation increased plasma [NO3−] and nitrite [NO2−] in both O and YG compared with PLA (more than sevenfold; all P ≤ 0.02). No changes were observed in MVC, Twpot, and Db100 force after BR compared with PLA in both YG and O. Only in O, Db100 area under the curve (−7 ± 6 N·s change from PLA) and half relaxation time (−0.05 ± 0.06 s change from PLA) were significantly reduced, and time to exhaustion (+32 ± 43 s change from PLA) was significantly longer (all P

• Voluntary Exercise Attenuates Tumor Growth in a Preclinical Model of Castration-Resistant Prostate Cancer

  Purpose To examine the effects of voluntary wheel running on tumor growth and explore potential intratumoral molecular pathways responsible for the beneficial effects of voluntary wheel running on tumor formation and progression in a mouse model of castration-resistant prostate cancer (CRPC). Methods Male immunodeficient mice (SCID) were castrated and subcutaneously inoculated with human CWR-22RV1 cancer cells to construct CRPC xenograft model before assigned to either voluntary wheel running (VWR) or sedentary (SED) group (n = 6/group). Tumor size was measured and calculated throughout the study. After 3 wk, tumor tissues were collected. mRNA expression of markers of DNA replication, androgen receptor (AR) signaling, and mitochondrial dynamics was determined by quantitative real-time polymerase chain reaction. Protein expression of mitochondrial dynamics was determined by Western blotting. Finally, transcriptomics analysis was performed using the tumor tissues. Results Voluntary wheel running resulted in smaller tumor volume at the initial stage and attenuated tumor progression throughout the time course (P

• In Vivo Biomechanical Interactions between Bones, Patellar Tendon, and Cartilage Surfaces at the Knee during Cycling

  Purpose Stationary cycling is essential in rehabilitation programs for various patient groups, such as knee osteoarthritis and cruciate ligament injuries and reconstruction. The study aimed to measure in vivo the 3D rigid-body and articular surface kinematics of the knee and the patellar tendon orientations during stationary cycling and isolated flexion–extension exercise in healthy young adults using a model-based tracking approach with dual-plane fluoroscopy. Methods Ten healthy left knees were imaged by computed tomography and magnetic resonance imaging to reconstruct subject-specific volumetric bone–cartilage models. The 3D rigid-body and articular surface kinematics and patellar tendon angles during stationary cycling and isolated knee flexion–extension exercise were measured in vivo using a dual-plane fluoroscopy with a voxel-based registration method, compared between tasks and between power and recovery phases. Results Significant differences in the rigid-body and surface kinematics and patellar tendon orientations were found between the power and recovery phases and between the power phase and isolated knee extension. Compared with the recovery phase, the power phase showed significantly greater external rotations, adductions, and posterior translations for flexions greater than 45° (P

• Bone Health of Female Elite Cyclists Is Characterized by Impaired Cortical and Trabecular Microarchitecture

  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 MD, 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.

• Temporal Trends and Projected Daily Step Count from 213,924 Pedometer Data in a Nationally Representative Japanese Population

  Purpose This study aimed to describe trends in the daily number of steps taken by the Japanese population from 1995 to 2019, using data from the National Health and Nutrition Survey Japan (NHNS-J), and to project step counts for 2032, the target year of the Health Japan 21 (HJ21) third term, while assessing the feasibility of national physical activity goals. Methods We analyzed individual, pedometer-based daily step count data from 213,924 participants between 1995 and 2019. Age-adjusted average daily step counts were calculated, then linear regression model was used to project daily step counts for 2032, stratified by age (20–64 yr, 65+ yr) and gender. Results The average number of steps taken by the Japanese population has shown a consistent decline since 2000. The projected daily step counts (95% confidence interval [CI]) for 2032 were as follows: 7499 (6854–8144) steps per day for men 20–64 yr old, 5038 (4091–5985) steps per day for men 65+ yr old, 6073 (5277–6869) steps per day for women 20–64 yr old, and 4620 (3749–5490) steps per day for women 65+ yr old. Significant declines were observed in women 20–64 yr old (beta = −45.8 steps per year, 95% CI = −86.4 to −15.2). The new step count targets set by HJ21 (8000 steps per day for younger adults and 6000 steps per day for older adults) are 6.1% to 26.9% higher than the projected values, particularly for women. Conclusions Daily step counts in Japan have shown a long-term decline, particularly among women. The projected decline in step counts indicates that the new step targets set by HJ21 may be challenging to achieve, particularly for women. Future public health initiatives should prioritize promoting physical activity in this population.