Medicine and Science in Sports and Exercise最新文献

Objective: This study aimed to identify potential changes in cardiorespiratory fitness among athletes who had previously been infected with SARS-CoV-2.

Methods: In this prospective observational multicenter hybrid study (CoSmo-S), cardiopulmonary exercise testing on treadmills or bicycle ergometers involving 2314 athletes (39.6% female) was conducted. German federal squad members (59.6%) and non-squad athletes were included in the study. 1170 (37.2% female) subjects were tested positive for SARS-CoV-2 via PCR from which we had pre-SARS-CoV-2 infection examinations available for 289 subjects. Mixed effect models were employed to analyze amongst others the following dependent variables: Power output at individual anaerobic threshold (POIAT/kg), maximal power output (POmax/kg), measured V̇O2max/kg, heart rate at individual anaerobic threshold (HRIAT) and maximal heart rate (HRmax).

Results: A SARS-CoV-2 infection was associated with a decrease in POIAT/kg (-0.123 W/kg, p < 0.001), POmax/kg (-0.099 W/kg, p = 0.002), measured V̇O2max/kg (-1.70 ml/min/kg, p = 0.050) and an increase HRIAT (2.50 b/min, p = 0.008), HRmax (2.59 b/min, p < 0.001) within the first 60 days after SARS-CoV-2 infection. Using the pandemic onset in Germany as longitudinal reference point, the healthy control group showed no change over time in these variables respectively an increase in POmax (+0.126 W/kg, p = 0.039) during the first 60 days after the reference point. Subgroup analyses showed that both squad members and endurance athletes experienced greater decreases in cardiorespiratory fitness compared to non-squad members respectively athletes from explosive power sports.

Conclusions: A SARS-CoV-2 infection is associated with a decline in cardiorespiratory fitness in athletes for approximately 60 days. Potential factors contributing to this outcome seem to be cardio-pulmonary and vascular alterations in consequence of SARS-CoV-2. A minor effect on cardiorespiratory fitness has training interruption due to acute symptoms and/or quarantine.

Objective: The primary aim of this study was to assess the efficacy of the weight, urine, thirst (WUT) framework in predicting dehydration after a body water manipulation protocol, while concurrently determining the individual and interactive contributions of the model components.

Methods: The total study sample was 93 participants (female, n = 47), recruited from two institutions. Phase 1 involved collecting daily hydration measures from free-living participants (Study 1, 58 participants for 3 days; Study 2, 35 participants for 7 days). Phase 2 entailed a two-hour passive heating protocol, where participants from Study 2 were randomly assigned to one of three groups that manipulated total body water over 24-hours using passive heating and fluid restriction. During each Phase, participants provided urine samples, underwent body mass measurements, and completed questionnaires pertaining to thirst perception. Morning and 24-hour urine samples were assessed for color, osmolality, and specific gravity. Differences between intervention groups, based on the probability of hydration status, were examined (ANOVA) and ridge regression analysis assessed the relative importance of variables within the WUT model.

Results: The study revealed significant differences among the intervention groups for predicted probability of dehydration, as determined by changes in body mass (p = 0.001), urine color (p = 0.044), and thirst perception (p < 0.001). Binomial ridge regression indicated that change in body mass (58%) and thirst perception (26%) were the most influential predictors of dehydration.

Conclusions: These data support use of an enhanced version of the WUT model, underscoring the significance of changes in body mass and thirst perception in the assessment of hydration status.

Objective: Existing literature indicates that females generally demonstrate higher fatigue resistance than males during isometric contractions. However, when it comes to single-limb dynamic exercises, the intricate interplay between performance fatigability (PF), cardiovascular responses, and muscle metabolism in relation to sex differences remains underexplored.

Purpose: This study investigates how sex affects the relationship between muscle oxidative characteristics and the development of PF during dynamic single-leg exercise.

Methods: Twenty-four young healthy participants (12 males vs. 12 females) performed a constant-load single-leg knee extension task (85% peak power output; 60 rpm) to exhaustion (TTE). Neuromuscular assessments via transcranial magnetic and peripheral stimulations were conducted pre- and post-exercise to evaluate central and peripheral factors of PF. Vastus lateralis muscle biopsies were obtained for mitochondrial respiration and immunohistochemistry analyses.

Results: Participants performed similar total work (28 ± 7 vs. 27 ± 14 kJ, p = 0.81) and TTE (371 ± 139 vs. 377 ± 158 sec, p = 0.98); after the TTE, females' maximal isometric voluntary contraction (MVIC: -36 ± 13 vs. -24 ± 9 %, p = 0.006) and resting twitch (RT: (-65 ± 9 vs. -40 ± 24 %, p = 0.004) force declined less. No differences were observed in supraspinal neuromuscular factors (p > 0.05). During exercise, the cardiovascular responses differed between sexes. Although fiber type composition was similar (type I: 47 ± 13 vs. 56 ± 14 %, p = 0.11), males had lower mitochondrial net oxidative capacity (61 ± 30 vs. 89 ± 37, p = 0.049) and higher Complex II contribution to maximal respiration (CII; 59 ± 8 vs. 48 ± 6%, p < 0.001), which correlated with the decline in MVIC (r = -0.74, p < 0.001) and RT (r = -0.60, p = 0.002).

Conclusions: Females display greater resistance to PF during dynamic contractions, likely due to their superior mitochondrial efficiency and lower dependence on mitochondrial CII activity.

Purpose: Non-steroidal anti-inflammatory drugs (NSAID) are associated with increased stress fracture risk, potentially due to inhibiting the adaptive bone formation responses to exercise. This study investigated if a single, maximal dose of three different NSAIDs alters bone formation biomarker response to strenuous exercise.

Methods: In a randomized, counter-balanced order, 12 participants (10 male, 2 female), performed four bouts of plyometric jumps, each separated by at least one week. Two hours before exercise, participants consumed either placebo (PLA) or NSAID: Ibuprofen (IBU, 800 mg), celecoxib (CEL, 200 mg), flurbiprofen (FLU, 100 mg). Blood was collected before (PRE), and at 0, 15, 60, 120, and 240 minutes post-exercise. Parathyroid hormone (PTH), ionized calcium (iCa), procollagen type 1 N-terminal propeptide (P1NP), bone alkaline phosphatase (BAP), osteocalcin (OCN), C-terminal telopeptide of type 1 collagen (CTX), tartrate resistant acid phosphatase (TRAP5b), and sclerostin (SCL) were measured. Prostaglandin E2 metabolite (PGE2M) and creatinine (Cr) were measured in urine. Data were analyzed using repeated measures ANOVA and area under the curve analysis (AUC). Data are mean ± SD.

Results: There was an exercise effect for P1NP, BAP, OCN, CTX, TRAP5b, SCL, OPG, PTH, and iCa (all p < 0.05), but no NSAID treatment effect for any biomarker (all p > 0.05). AUC analyses were not different for any biomarker (p > 0.05). PGE2M was higher during the PLA trial (322 ± 153 pg/mg Cr, p < 0.05) compared to IBU (135 ± 83 pg/mg), CEL (202 ± 107 pg/mg), and FLU (159 ± 74 pg/mg).

Conclusions: Plyometric exercise induced changes in bone metabolism, but the responses were unaltered by consuming NSAIDs two hours before exercise.

Purpose: This study compared the effects of off- and on-bike resistance training (RT) on endurance cycling performance as well as muscle strength, power and structure.

Methods: Well-trained male cyclists were randomly assigned to incorporate two sessions/week of off- (full squats, n = 12) or on-bike (all-out efforts performed against very high resistances and thus at very low cadences, n = 12) RT during 10 weeks, with all RT-related variables [number of sessions, sets, and repetitions, duration of recovery periods, and relative loads (70% of one-repetition maximum)] matched between the two groups. A third, control group (n = 13) did not receive any RT stimulus but all groups completed a cycling training regime of the same volume and intensity. Outcomes included maximum oxygen uptake (V̇O2max), off-bike muscle strength (full squat) and on-bike ('pedaling') muscle strength and peak power capacity (Wingate test), dual-energy X-ray absorptiometry-determined body composition (muscle/fat mass), and muscle structure (cross-sectional area, pennation angle).

Results: No significant within/between-group effect was found for V̇O2max. Both the off- (mean Δ = 2.6-5.8%) and on-bike (4.5-7.3%) RT groups increased squat and pedaling-specific strength parameters after the intervention compared to the control group (-5.8--3.9%) (p < 0.05) with no significant differences between them. The two RT groups also increased Wingate performance (4.1% and 4.3%, respectively, vs. -4.9% in the control group, p ≤ 0.018), with similar results for muscle cross-sectional area (2.5% and 2.2%, vs. -2.3% in the control group, p ≤ 0.008). No significant within/between-group effect was found for body composition. ConclusionsThe new proposed on-bike RT could be an effective alternative to conventional off-bike RT training for improving overall and pedaling-specific muscle strength, power, and muscle mass.

Introduction: The effect of eccentric exercise-induced muscle damage (EIMD) on cycling efficiency is unknown. The aim of the present study was to assess the effect of EIMD on gross and delta efficiency and the cardiopulmonary responses to cycle ergometry.

Methods: Twenty-one recreational athletes performed cycling at 70%, 90%, and 110% of the gas exchange threshold (GET) under control conditions (Control) and 24 h following an eccentric damaging protocol (Damage). Knee extensor isometric maximal voluntary contraction, potentiated twitch ( Qtw,pot ), and voluntary activation were assessed before Control and Damage. Gross and delta efficiency were assessed using indirect calorimetry, and cardiopulmonary responses were measured at each power output. Electromyography root-mean-square (EMG RMS ) during cycling was also determined.

Results: Maximal voluntary contraction was 25% ± 18% lower for Damage than Control ( P < 0.001). Gross efficiency was lower for Damage than Control ( P < 0.001) by 0.55% ± 0.79%, 0.59% ± 0.73%, and 0.60% ± 0.87% for 70%, 90%, and 110% GET, respectively. Delta efficiency was unchanged between conditions ( P = 0.513). Concurrently, cycling EMG RMS was higher for Damage than Control ( P = 0.004). An intensity-dependent increase in breath frequency and V̇ E /V̇CO 2 was found, which were higher for Damage only at 110% GET ( P ≤ 0.019).

Conclusions: Thus, gross efficiency is reduced following EIMD. The concurrently higher EMG RMS suggests that increases in muscle activation in the presence of EIMD might have contributed to reduced gross efficiency. The lack of change in delta efficiency might relate to its poor reliability hindering the ability to detect change. The findings also show that EIMD-associated hyperventilation is dependent on exercise intensity, which might relate to increases in central command with EIMD.

Purpose: Despite its susceptibility to muscle fatigue, combined neuromuscular electrical stimulation (NMES) and blood flow restriction (BFR) are effective regimens for managing muscle atrophy when traditional resistance exercises are not feasible. This study investigated the potential of low-level laser therapy (LLLT) in reducing muscle fatigue after the application of combined NMES and BFR.

Methods: Thirty-six healthy adults were divided into control and LLLT groups. The LLLT group received 60 J of 850-nm wavelength LLLT before a training program of combined NMES and BFR of the nondominant extensor carpi radialis longus (ECRL). The control group followed the same protocol but received sham laser therapy. Assessments included maximal voluntary contraction, ECRL mechanical properties, and isometric force tracking for wrist extension.

Results: The LLLT group exhibited a smaller normalized difference in maximal voluntary contraction decrement (-4.01 ± 4.88%) than the control group (-23.85 ± 7.12%) ( P < 0.001). The LLLT group demonstrated a smaller decrease in muscle stiffness of the ECRL compared with the control group, characterized by the smaller normalized changes in frequency ( P = 0.002), stiffness ( P = 0.002), and relaxation measures ( P = 0.011) of mechanical oscillation waves. Unlike the control group, the LLLT group exhibited a smaller posttest increase in force fluctuations during force tracking ( P = 0.014), linked to the predominant recruitment of low-threshold MU ( P < 0.001) without fatigue-related increases in the discharge variability of high-threshold MU ( P > 0.05).

Conclusions: LLLT preexposure reduces fatigue after combined NMES and BFR, preserving force generation, muscle stiffness, and force scaling. The functional benefits are achieved through fatigue-resistant activation strategies of motor unit recruitment and rate coding.

Introduction: The purpose of our report was to use a Random Forest classification approach to predict the association between transcutaneous electrical nerve stimulation (TENS) and walking kinematics at the stride level when middle-aged and older adults performed the 6-min test of walking endurance.

Methods: Data from 41 participants (aged 64.6 ± 9.7 yr) acquired in two previously published studies were analyzed with a Random Forest algorithm that focused on upper and lower limb, lumbar, and trunk kinematics. The four most predictive kinematic features were identified and utilized in separate models to distinguish between three walking conditions: burst TENS, continuous TENS, and control. SHAP analysis and linear mixed models were used to characterize the differences among these conditions.

Results: Modulation of four key kinematic features-toe-out angle, toe-off angle, and lumbar range of motion (ROM) in coronal and sagittal planes-accurately predicted walking conditions for the burst (82% accuracy) and continuous (77% accuracy) TENS conditions compared with control. Linear mixed models detected a significant difference in lumbar sagittal ROM between the TENS conditions. SHAP analysis revealed that burst TENS was positively associated with greater lumbar coronal ROM, smaller toe-off angle, and less lumbar sagittal ROM. Conversely, continuous TENS was associated with less lumbar coronal ROM and greater lumbar sagittal ROM.

Conclusions: Our approach identified four kinematic features at the stride level that could distinguish between the three walking conditions. These distinctions were not evident in average values across strides.

Purpose: Prior evidence has shown that neural factors contribute to the loss of muscle force after skeletal muscle disuse. However, little is known about the specific neural mechanisms altered by disuse. Persistent inward current (PIC) is an intrinsic property of motoneurons responsible for prolonging and amplifying the synaptic input, proportionally to the level of neuromodulation, thus influencing motoneuron discharge rate and force production. Here, we hypothesized that short-term unilateral lower limb suspension (ULLS) would reduce the neuromodulatory input associated with PIC, contributing to the reduction of force generation capacity. In addition, we tested whether physical exercise would restore the force generation capacity by reestablishing the initial level of neuromodulatory input.

Methods: In 12 young adults, we assessed maximal voluntary contraction pre- and post-10 d of ULLS and after 21 d of active recovery (AR) based on resistance exercise. PIC was estimated from high-density surface electromyograms of the vastus lateralis muscle as the delta frequency (Δ F ) of paired motor units calculated during isometric ramped contractions.

Results: The values of Δ F were reduced after 10 d of ULLS (-33%, P < 0.001), but were fully reestablished after the AR (+29.4%, P < 0.001). The changes in estimated PIC values were correlated ( r = 0.63, P = 0.004) with the reduction in maximal voluntary contraction after ULLS (-29%, P = 0.002) and its recovery after the AR (+28.5%, P = 0.003).

Conclusions: Our findings suggest that PIC estimates are reduced by muscle disuse and may contribute to the loss of force production and its recovery with exercise. Overall, this is the first study demonstrating that, in addition to peripheral neuromuscular changes, central neuromodulation is a major contributor to the loss of force generation capacity after disuse, and can be recovered after resistance exercise.

Purpose: Habitual strength and power-demanding activities of daily life may support the maintenance of adequate lower extremity functioning with aging, but this has been sparingly explored. Hence, we examined whether the characteristics of free-living sit-to-stand (STS) transitions predict a decline in lower extremity functioning over a 4-yr follow-up.

Methods: A total of 340 community-dwelling older adults (60% women; age 75, 80, or 85 yr) participated in this prospective cohort study. At baseline, a thigh-worn accelerometer was used continuously (3-7 d) to monitor the number and intensity of free-living STS transitions. A decline in lower extremity functioning was defined as a drop of ≥2 points in the Short Physical Performance Battery (SPPB) from baseline to follow-up. Maximal isometric knee extension strength was measured in the laboratory.

Results: Eighty-five participants (75% women) declined in SPPB over 4 yr. After adjusting for age, sex, and baseline SPPB points, higher free-living peak STS angular velocity (odds ratio (OR), 0.70; 95% confidence interval (CI), 0.52-0.92, per 20°·s -1 increase) protected against a future decline. When adjusting the model for maximal isometric knee extension strength, the statistical significance was attenuated (OR = 0.72; 95% CI = 0.54-0.96, per 20°·s -1 increase).

Conclusions: Performing STS transitions at higher velocities in the free-living environment can prevent a future decline in lower extremity function. This indicates that changes in daily STS behavior may be useful in the early identification of functional loss. Free-living peak STS angular velocity may be a factor underlying the longitudinal association of lower extremity strength and performance.