Medicine and Science in Sports and Exercise最新文献

Purpose: To determine 1) whether the relationship between isometric training and muscle growth depends on baseline blood flow or is mediated by a change in blood flow, and 2) whether muscle growth mediates changes in maximal isometric strength.

Methods: A total of 179 participants were randomized into low-intensity isometric handgrip exercise (LI), low-intensity isometric handgrip exercise with blood flow restriction (LI-BFR), maximal handgrip exercise (MAX), and a non-exercise control (CONTROL). Muscle thickness, strength, and resting limb blood flow were measured before and after the 6-wk intervention.

Results: Baseline blood flow did not moderate training effects on muscle thickness changes (MTHchg) ( P = 0.666), and moderated mediation tests were nonsignificant. Although the LI-BFR group showed a significant effect on MTHchg ( P = 0.018), MTHchg was not significantly related to handgrip strength change (HGchg) ( P = 0.281), suggesting no mediation of the training-to-strength effect by MTHchg. Both the LI-BFR ( P = 0.004) and MAX ( P < 0.001) groups exhibited positive direct effects on HGchg compared with CONTROL. Furthermore, there were no differences between training groups and CONTROL on blood flow change (BFchg), BFchg and MTHchg were not significantly related, and neither BFchg nor MTHchg predicted HGchg, providing no evidence for mediated pathways.

Conclusions: Muscle growth may not have occurred to an extent that would require vascular adaptation. Training maximally induced the greatest strength adaptations but was seemingly not driven by muscle growth.

Background: Reactive and external visual-cognitive demands are prevalent in sport and likely contribute to anterior cruciate ligament (ACL) injury scenarios. However, these demands are absent in common return-to-sport assessments. This disconnect leaves a blind spot for determining when an athlete can return to sport with mitigated re-injury risk.

Purpose: To characterize relationships between patient-reported outcome measures (PROMs) and cognitive-task interference (i.e., cognitive demands exacerbating neuromuscular impairments) for biomechanical predictors of second ACL injuries during jump landings that involved rapid unanticipated decision making.

Methods: Thirty-six persons following primary ACL reconstruction (ACLR; 26 females/10 males, 19.8 ± 1.8 yr; 1.71 ± 0.1 m; 69.6 ± 12.8 kg, 1.5 ± 0.6 yr post-ACLR; Tegner: 6.8 ± 1.8) participated. PROMs of ACL-RSI and the Forgotten Joint Score-12 Knee (FJS-12) were selected to assess altered psychological state (e.g., confidence, attention toward knee). Jumping tasks under anticipated and unanticipated secondary jump directions were performed. Biomechanical variables were dual-task changes (unanticipated - anticipated) in 1) uninvolved limb hip rotator impulse (DTC_Uni-HRot_Imp), 2) asymmetry of knee extensor moment at initial contact (DTC_KEM_Asym), and 3) range of involved knee abduction angle (DTC_KAbA_Range). Regression models tested for relationships between PROMs and the dual-task change in biomechanical variables.

Results: ACL-RSI (DTC_Uni-HRot_Imp ( P < 0.001)) and FJS-12 (DTC_KAbA_Range ( P = 0.001)) had significant relationships with dual-task change in the opposite direction as expected (worse PROM ➔ less dual-task change). A follow-up analysis indicated that dual-task change was inversely correlated with the baseline estimates for kinetic biomechanical variables (less risky single-task biomechanics ➔ greater dual-task change for Uni-HRot_Imp and KEM_Asym).

Conclusions: The collective results are consistent with higher functioning participants (better PROMs) who also demonstrate desirable biomechanics during single-task conditions being prone to demonstrating the greatest risk-associated DTC in unanticipated scenarios.

Purpose: Theta-burst stimulation (TBS) over the primary motor cortex modulates activity of the underlying neural tissue, but little is known about its consequence on neuromuscular fatigue and its neural correlates. This study aimed to compare the effects of facilitatory versus inhibitory TBS on the neuromuscular fatigue and excitability/inhibition of the corticospinal pathway in an unfatigued/fatigued muscle.

Methods: The effects of three TBS protocols (facilitatory/intermittent: iTBS; inhibitory/continuous: cTBS, and sham: sTBS) were tested on exercise performance, neuromuscular function, and corticospinal excitability and inhibition in 20 young healthy participants. Transcranial magnetic and peripheral electrical stimulations were used at baseline, following TBS (unfatigued state), and after a fatiguing sustained contraction (fatigued state) at 35% of the maximal voluntary isometric contraction (MVIC) of the elbow flexors.

Results: Time-to-task failure was shorter for cTBS (142 ± 51 s) and longer for iTBS (214 ± 68 s) compared with sTBS (173 ± 65 s) ( P < 0.05). In an unfatigued state, cTBS reduced MVIC and voluntary activation (VA), increased motor-evoked potential, and silent period ( P < 0.05), whereas iTBS did not cause any change. In a fatigued state, MVIC and VA decreased in all TBS sessions ( P < 0.05). However, the reduction in VA was larger after cTBS (Δ -18 ± 18%) compared with iTBS (Δ-3 ± 5%), and sTBS (Δ-9 ± 9%) ( P < 0.001). Furthermore, the increase in motor-evoked potential and silent period were greater for cTBS ( P < 0.05), compared with iTBS and sTBS ( P < 0.05).

Conclusions: Facilitatory TBS augments exercise performance that is independent of central parameters and corticospinal mechanisms, whereas inhibitory TBS attenuates exercise performance through an exacerbation in the development of central fatigue and possibly intracortical inhibition.

Purpose: This study compared the physiological effects of a moderate-intensity interval training (MIT) microcycle followed by an active recovery period (collectively termed MITblock) 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 (VO2max), 70.5 (4.6) mL·min-1·kg-1) completed both MITblock and REG. The MIT microcycle involved six interval sessions over seven days with 5-7 × 10-14 min work intervals at a perceived exertion (RPE) of 14-15 on the Borg 6-20 scale. A six-day 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 (PO15min), power output at 4 mmol·L-1 [blood lactate] (PO4mmol), 1 min peak power output during incremental testing (POVO2max), and VO2max.

Results: Although the Training Impulse (TRIMP) score was not different between MITblock and REG (1944 (436) vs. 1800 (232), respectively; p = 0.27), MITblock resulted in significantly greater improvements than REG in PO4mmol (4.0 (4.4)% vs. -1.3 (3.7)%, p < 0.01), POVO2max (2.5 (4.5)% vs. -0.7 (3.9)%, p < 0.01) and VO2max (2.0 (3.9)% vs. 0.0 (3.5)%, p = 0.05). Changes in PO15min were not statistically different between MITblock and REG (3.9 (8.3)% vs. 0.2 (6.8)%, p = 0.14). During MIT intervals, RPE was 14.4 (0.3), corresponding to 66 (5)% of POVO2max, 85 (3)% of maximal heart rate, and 2.8 (1.1) mmol·L-1 [blood lactate].

Conclusions: Six moderate-intensity interval sessions over seven days, followed by a six-day active recovery period, induce improvements in endurance performance indicators compared to a time-matched regular training period in well-trained cyclists.

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. Since 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 yrs, O) and 11 young (26 ± 2 yrs, YG) adults consumed either NO3--rich beetroot juice (BR) or placebo (PLA), for 7 days. 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 non-dominant leg.

Results: BR supplementation increased plasma [NO3-] and nitrite [NO2-] in both O and YG compared to PLA (more than 7-fold; all P ≤ 0.02). No changes were observed in MVC, Twpot, and Db100 force after BR compared to 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 < 0.02) after BR. In O, BR also significantly increased submaximal force produced by trains of electrical pulses (P < 0.001).

Conclusions: NO3- supplementation positively affects muscle contractile proprieties, submaximal electrically evoked force production and fatigue resistance in older adults while these positive results were not found in young.

Purpose: We sought to evaluate the effect of intensive physical training on left ventricular (LV) hemodynamic forces (HDF) in athletes.

Methods: Forty professional endurance athletes were evaluated at the beginning of their training cycle (off-season) and after a period of aerobic isotonic dynamic exercise (peak training period) using cardiac magnetic resonance (CMR). Images were analyzed off-line using dedicated software. LV HDF for the whole cardiac cycle and the different cardiac phases were measured. Standard statistics were used to compare off-season and peak training period values.

Results: The average sport experience was 11 ± 7 years. There were no differences in LV volumes, stroke volume, LVEF and LV mass between off-season and peak training CMR. Similarly, there were no changes induced by physical training in the strain parameters. Physical training induced a significant increase of the longitudinal HDF (18.7 vs 21.2, p = 0.023) and an increase of the transverse HDF (3.4 vs 4.0, p = 0.048) throughout the entire heartbeat. After physical training, the peak values and the hemodynamic work (expressed as AUC) of the first part of the systole were significantly higher compared to off-season values (63.9 vs 53.9, p = 0.034; 4.67 vs 3.79, p = 0.015, respectively). The difference in the elastic rebound between off-season and peak training (-0.22 vs -0.37) did not reach statistical significance (p = 0.056).

Conclusions: Intense physical training induces an increase in LV HDF of the first part of the systole and of the elastic rebound phase, independent from geometric cardiac remodeling.

Purpose: This study investigated the effects of a 6-week eccentrically-biased training intervention between Romanian deadlift (RDL) and Nordic hamstring exercises (NHE) on regional hamstring muscle architecture and morphology.

Methods: Participants were randomly allocated to an RDL or NHE intervention group and trained twice per week for 6 weeks followed by a 2-week detraining period. Biceps femoris long head (BFlh) architecture (fascicle length [FL] and pennation angle [PA]) and muscle thickness (MT) were measured using extended-field-of-view ultrasound. Anatomical cross-sectional areas (ACSA) of BFlh, semimembranosus, and semitendinosus were also assessed via ultrasound. Muscle architecture and morphology were measured proximally, in the middle, and distally along the thigh. Separate linear mixed effects models were run for each outcome.

Results: Thirty-two healthy participants (15 females, 17 males) aged 20.8 (0.9) years were enrolled and allocated to RDL (n = 16) or NHE (n = 16) groups. Following the intervention, BFlh FL increased (0.80 [0.6, 1.0] cm (9%), p < 0.001), while PA decreased uniformly across all regions (-1.2° [-1.5, -0.9] (10%), p < 0.001) and MT did not change (p = 0.29). Both BFlh FL and PA returned to baseline after detraining. No differences were observed between groups for changes in FL (p = 0.55), PA (p = 0.74), or MT (p = 0.48). Hamstrings ACSA increased after the intervention (0.78 cm2 [0.45, 1.11] (10%), p < 0.001) and remained elevated after detraining. There were no significant differences in ACSA between groups after the intervention (p = 0.60).

Conclusions: Changes in FL, PA, and ACSA are consistent between an eccentrically-biased RDL and NHE intervention. These findings provide practitioners choice in exercise selection for eliciting adaptations relevant to hamstring injury prevention.

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 towards 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 (MVPA).

Methods: We assessed physical behaviours across eight consecutive days using thigh-worn accelerometers among adults from the Nijmegen Exercise Study. Multiple cardiometabolic risk factors were assessed and categorised 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, i.e. <8.5, 8.5-10, and > 10 hours/day.

Results: We included 1,041 participants (64 (standard deviation 11) years; 39.5% female). Reallocating sedentary time towards LIPA was associated with improvements in anthropometrics, some cardiovascular biomarkers, and glucose metabolism; e.g., replacing 60 minutes/day of sedentary time with LIPA was associated with improvements in BMI (-0.28 (-0.42, -0.13) kg/m 2 ), eGFR (0.68 (0.15, 1.20) mL/min/1.73m 2 ), and glucose (-0.05 (-0.08, -0.03) mmol/L). Trends suggested that reallocation benefits were strongest in those with >8.5 hours/day of sedentary time. Proportionally similar replacements of sedentary time with either LIPA or MVPA 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.

Introduction: Subthreshold depression represents a prodromal stage of major depressive disorder and may be associated with abnormalities in brain structural and functional networks. While studies have shown that mind-body exercises such as Tai Chi can alleviate subthreshold depression, the underlying mechanisms remain unclear. Purpose: This study aimed to explore the potential mechanisms of Tai Chi for improving subthreshold depression from the perspective of structure-function coupling of brain networks.

Methods: This randomized controlled trial enrolled 112 individuals with subthreshold depression, randomly assigning them to either the Tai Chi group or a waitlist control group. Participants in the Tai Chi group received three 60-minute training sessions per week for 12 weeks. Outcome measures included assessments of negative mood symptoms, such as depression and stress, as well as structural and functional brain imaging.

Results: After accounting for the dropout of nine participants, a total of 103 individuals were included in the final statistical analysis. Compared to the control group, participants in the Tai Chi group exhibited significant reductions in depression, stress, and anxiety scores. Network analyses revealed a decrease in structure-function coupling and characteristic path length within the frontoparietal network following Tai Chi practice. Further nodal analyses indicated a significant reduction in nodal degree and efficiency in the left prefrontal cortex and posterior cingulate gyrus, while increases were observed in the right lateral prefrontal cortex. Partial correlation analysis demonstrated a significant negative correlation between right prefrontal efficiency and anxiety scores.

Conclusions: The benefits of Tai Chi on subthreshold depression may be related to modulating the structure-function coupling of the frontoparietal network and increasing nodal efficiency.