Search

The present study aims to investigate effects of caffeine ingestion and sex difference on muscle performance, delayed-onset muscle soreness (DOMS), and various biomarkers under exercise-induced muscle damage (EIMD). Twenty (10 male and 10 female) healthy elite college athletes were recruited. Participants ingested either caffeine (6 mg/kg) or a placebo in a randomized, double-blind, and counterbalanced fashion at 24 and 48 h following EIMD. Muscle performance, DOMS, and blood samples were taken an hour before and an hour after supplementation. Caffeine ingestion restored impaired maximal voluntary isometric contractions (MVIC: 10.2%; MVICpost: 7.2%, both P < 0.05) during EIMD across both sexes. Following caffeine ingestion during MVIC, while affected by EIMD, an interaction was found in DOMS and serum K+ (both P < 0.05), with males showing greater attenuation (21.5 and 16.9%, respectively) compared with females (4.6 and 1.3%, respectively). DOMS demonstrated an inverse correlation with MVIC after caffeine ingestion both overall and among male athletes ( r = −0.34 and −0.54, respectively; P < 0.05) but not among female athletes ( r = −0.11; P > 0.05) under EIMD. In addition, caffeine ingestion increased postexercise serum glucose and lactate concentrations across both sexes (both P < 0.05). This is the first study to show that male athletes, compared with female athletes, experience a greater reduction in DOMS during enhanced MVIC when caffeine was consumed, suggesting men might receive greater ergogenic effects from caffeine when affected by EIMD. Furthermore, caffeine ingestion was able to restore impaired muscle power among elite collegiate athletes across both sexes. NEW & NOTEWORTHY Exercise-induced muscle damage (EIMD) reduces anaerobic/aerobic performance and increases delayed-onset muscle soreness (DOMS) during exercise. We show that acute caffeine supplementation at a dosage of 6 mg/kg seems to facilitate recovery of anaerobic muscle power and attenuate DOMS after EIMD across both sexes. Furthermore, male athletes, compared with female athletes, when caffeine was prescribed, experience a greater reduction in DOMS with better restoration of impaired maximal voluntary isometric contractions. This suggests that male athletes might benefit from the ergogenic effect of acute caffeine supplementation after the onset of EIMD.

Low-intensity eccentric contractions with a load corresponding to 10% of maximal voluntary isometric contraction strength (10% EC) attenuate muscle damage in a subsequent bout of higher-intensity eccentric contractions performed within 2 weeks for the elbow flexors, knee flexors and knee extensors. However, it is not known whether this strategy could be applied to other muscles. This study investigated whether 10% EC would confer damage protective effect on high-intensity eccentric contractions (80% EC) for nine different muscle groups. Untrained young men were placed to an experimental or a control group (n = 12/group). Experimental group performed 50 eccentric contractions with a load corresponding to 10% EC at 2 days prior to 50 eccentric contractions with 80% EC for the elbow flexors and extensors, pectoralis, knee flexors and extensors, plantar flexors, latissimus, abdominis and erector spinae. Control group performed 80% EC without 10% EC. Changes in maximal voluntary isometric contraction strength (MVC) and muscle soreness, plasma creatine kinase (CK) activity and myoglobin concentration after 80% EC were compared between groups by a mixed-factor ANOVA. MVC recovered faster (e.g., 6–31% greater MVC at 5 days post-exercise), and peak muscle soreness was 36–54% lower for Experimental than Control group for the nine muscles (P

The purpose of the study was to investigate the adaptation process of hindlimb cortical bone subjected to free-fall landing training. Female Wistar rats (7 weeks old) were randomly assigned to four landing (L) groups and four age-matched control (C) groups (n = 12 per group): L1, L2, L4 L8, C1, C2, C4 and C8. Animals in the L1, L2, L4 and L8 groups were respectively subjected to 1, 2, 4 and 8 weeks of free-fall-landing training (40 cm height, 30 times/day and 5 days/week) while the C1, C2, C4 and C8 groups served as age-matched control groups. The tibiae of the L8 group were higher in cortical bone mineral content (BMC) than those in the C8 group (p < 0.05). Except for the higher bone mineralization over bone surface ratio (MS/BS, %) shown in the tibiae of the L1 group (p < 0.05), dynamic histomorphometry in the tibial and femoral cortical bone showed no difference between landing groups and their age-matched control groups. In the femora, the L1 group was lower than the C1 group in cortical bone area (Ct.Ar) and cortical thickness (Ct.Th) (p < 0.05); however, the L4 group was higher than the C4 group in Ct.Ar and Ct.Th (p

Background Whether active travel and public transportation, as opposed to private vehicle use, are related to physical activity levels and the risk of overweight in Asian countries is unclear. Thus, this study examined the associations of transportation-related physical activity involving three modes of travel and the risk of overweight among Taiwanese adults. Methods Data from 51,949 Taiwanese adults were used. The examined variables were objectively-measured height and body mass, self-reported main mode of travel (private vehicle, public transport, active travel), and time spent walking and cycling for transportation using the International Physical Activity Questionnaire-long version. Logistic regression modeling was performed. Results After adjustment for potential confounders, public transportation and active travel were found to be significantly associated with a higher probability of engaging in 150 min/wk of transportation-related physical activity (odds ratio (OR)=2.35, 95% confidence interval (CI): 2.21, 2.49; OR=6.31, 95% CI: 5.95, 6.69) and a lower risk of overweight (OR=0.84, 95% CI: 0.79, 0.90; OR=0.83, 95% CI: 0.78, 0.88) compared with traveling by private motor vehicle. Similar patterns were observed in men and women. Conclusions Using public transport might be as effective as active transportation to accumulate transport-related physical activity to achieve health-enhancing level and to be associated with lower odds of being overweight in Taiwanese adults. Encouraging public transportation use could promote physical activity and be considered a promising method of preventing overweight in both men and women.

This study compared nine resistance eccentric exercises targeting arm, leg, and trunk muscles in one session for changes in maximal voluntary isometric contraction strength (MVC), delayed onset muscle soreness (DOMS), plasma creatine kinase (CK) activity, and myoglobin (Mb) concentration after the first and second bouts. Fifteen sedentary men (20-25 years) performed 5 sets of 10 eccentric contractions with 80% of MVC load for the elbow flexors (EF), elbow extensors (EE), pectoralis, knee extensors (KE), knee flexors (KF), plantar flexors (PF), latissimus, abdominis, and erector spinae (ES) in a randomized order and repeated the same exercises 2 weeks later. MVC decreased at 1 (16%-57%) to 4 (13%-49%) days, DOMS developed (peak: 43-70 mm), and CK activity (peak: 23 238-207 304 IU/L) and Mb concentration showed large increases after the first bout. The magnitude of decrease in MVC was greater (P < 0.05) for EF, EE, and PEC than others and for KF than KE, PF, and ES. DOMS was greater (P < 0.05) for EF, EE, and ES than others. Changes in all measures were smaller (P < 0.05) after the second than the first bout, and the magnitude of the repeated bout effect was similar among the muscles. Plasma CK activity and Mb concentration did not increase significantly after the second exercise bout. It was concluded that muscle damage was greater for arm than leg muscles, and muscle proteins in the blood increased to a critical level after unaccustomed whole-body resistance exercises, but the magnitude of damage was largely attenuated for all muscles similarly after the second bout.

Although the time spent sitting in motorized vehicles has been determined to be adversely associated with cardiometabolic health, its association with other health indicators remains unclear. This study examined associations between traveling by private motorized vehicle and 4 indicators of physical fitness in adults. Data from 52,114 Taiwanese adults aged 20 to 65 years who participated in the 2013 National Adults Fitness Survey were used. The examined variables were height, body mass, and performance in modified sit-and-reach (flexibility), bent-leg sit-up (abdominal muscular strength and endurance), and a 3-min step test (cardiorespiratory endurance). Participants were asked on how many days they had used a private car or motorcycle for traveling from place to place and categorized as non-, occasional, and daily private motorized vehicle travelers. Logistic and linear regression models were used to examine associations between the categories of using private motorized vehicles to travel and physical fitness performance. After an adjustment for potential demographic and behavioral confounders, daily traveling by private motorized vehicle was associated with a higher probability of overweight (odds ratio = 1.18), lower performance of abdominal muscular strength and endurance (−0.37 times/min), and lower cardiorespiratory fitness (−0.60 physical fitness index) than was traveling that did not involve private motorized vehicles. The results suggest that in addition to unfavorable cardiorespiratory fitness and a risk of overweight, daily traveling by private motorized vehicle is associated with poor performance in abdominal muscular strength and endurance.

The purpose of the study was to investigate the adaptation process of hindlimb cortical bone subjected to free-fall landing training. Female Wistar rats (7 weeks old) were randomly assigned to four landing (L) groups and four age-matched control (C) groups (n = 12 per group): L1, L2, L4 L8, C1, C2, C4 and C8. Animals in the L1, L2, L4 and L8 groups were respectively subjected to 1, 2, 4 and 8 weeks of free-fall-landing training (40 cm height, 30 times/day and 5 days/week) while the C1, C2, C4 and C8 groups served as age-matched control groups. The tibiae of the L8 group were higher in cortical bone mineral content (BMC) than those in the C8 group (p < 0.05). Except for the higher bone mineralization over bone surface ratio (MS/BS, %) shown in the tibiae of the L1 group (p < 0.05), dynamic histomorphometry in the tibial and femoral cortical bone showed no difference between landing groups and their age-matched control groups. In the femora, the L1 group was lower than the C1 group in cortical bone area (Ct.Ar) and cortical thickness (Ct.Th) (p < 0.05); however, the L4 group was higher than the C4 group in Ct.Ar and Ct.Th (p

Previous studies have consistently reported a positive effect of acute exercise on cognition, particularly on executive function. However, most studies have focused on aerobic and resistant forms of exercise. The purpose of this study was to compare the effect of &lsquo, open-skill&rsquo, with &lsquo, closed-skill&rsquo, exercise (defined in terms of the predictability of the performing environment) on brain-derived neurotrophic factor (BDNF) production and task switching performance. Twenty young adult males participated in both closed (running) and open (badminton) skill exercise sessions in a counterbalanced order on separate days. The exercise sessions consisted of 5 min of warm up exercises followed by 30 min of running or badminton. The exercise intensity was set at 60% (&plusmn, 5%) of the heart rate reserve level (HRR) with HR being monitored by a wireless heart rate monitor. Blood samples were taken and participation in a task-switching paradigm occurred before and after each exercise session. Results showed no differences in serum BDNF or task-switching performance at the pre-test stage, however, badminton exercise resulted in significantly higher serum BDNF levels (a proxy for levels of BDNF in the brain) and near significant smaller global switching costs relative to running. This study has provided preliminary evidence in support the relative benefits of open-skills exercises on BDNF and executive function.

The primary purpose of this study was to investigate the effects of gender difference and caffeine supplementation to maximal voluntary isometric contractions (MVIC) and submaximal voluntary isometric contractions (T lim ). 10 male (age: 20.10 ± 2.18 years, BMI: 22.23±1.96 kg/m2) and 10 female (age: 19.90±0.99 years, BMI: 21.76±2.65 kg/m2) elite collegiate athletes were recruited. Subjects ingested caffeine (6 mg/kg) or a placebo in a randomized, double-blind, placebo-control, and counter-balanced fashion. MVIC and T lim were measured after supplementations. T lim result was calculated based on the time to exhaustion of isometric contraction with 50% MVIC. Fatigue index (FI%) referred to the MVIC tested 20 s after the cessation of T lim test, and was indexed by the percentage of MVIC decline. No significant interaction effect was found between the gender factor and the supplementation factor for all dependent variables. Compared to the placebo, caffeine supplementation significantly increased MVIC (5.9%) and T lim (15.5%) (p

The purpose of this study was to determine the effects of a mechanical loading course (short-term free-fall landing) on femoral geometry and biomechanical properties in growing rats. Thirty-two female Wistar rats (7-week-old) were randomly assigned to three groups: L30 (n = 11), L10 (n = 11) and CON (n = 10) groups. Animals in the L10 and L30 groups were subjected to a 5-day free-fall landing program in which animals were dropped from a height of 40cm 10 and 30 times per day, respectively. Landing ground reaction force (GRF) was measured on the 1(st) and 5(th) days of landing training. All animals were subjected to two fluorescent labeling injections on the days before and after the 5-day landing training. Three days after the last labeling injection, animals were sacrificed under deep anesthesia. Methods of dynamic histomorphometry, tissue geometry and tissue biomechanical measurements were used to investigate the response in femora. A significant decrease in peak GRF in the hind-limb was shown from day 1 to day 5. No significant difference was shown among groups in dynamic histomorphometry. Biomechanical property analyses showed significantly lower maximal energy and post-yield energy in the L10 and L30 groups as compared to the CON group (p0.05). Moreover, geometric measurements revealed that cross-sectional cortical areas and thicknesses were significantly lower in landing groups than in the CON group. Short-term (5-day) free-fall landing training resulted in minor compromised long bone tissue, as shown by reduced bending energy and cortical bone area but not in other mechanical properties or tissue measurements (e.g. weights and length) of growing female rats. Further studies would be valuable to investigate whether this compromised bone material represents the existence of a latency period in the adaptation of bone material to external mechanical loading. Key pointsShort-term free-fall landing causes compromised bone material as shown by reduced post-yield energy in long bones of rodents.The results of the current study suggest the existence of unsettled bone material after a short-term mechanical loading regime.The connection of the present animal study to the stress fractures occurring in young athletes needs to be clarified.

The purpose of this study is to investigate the effects of one- and four-week mechanical loading on the bones in young female rats. Seven-week-old female SD rats (n = 40) were randomly assigned into four groups, which were the 1WCON, 1WLAND, 4WCON, and 4WLAND groups (n = 10 for each). Animals of the 1WLAND and 4WLAND groups were respectively subjected to 1- and 4-week free-fall landing program, in which animals were free-fallen from a height of 40 cm for 10 times per day; 5 days per week. The 1WCON and 4WCON groups served as the time-matched control groups. Methods of histomorphometry, tissue geometry, and tissue weight were performed on the animals' femora and tibiae. Two-way (landing × time) ANOVA was used for statistical analysis (α = .05). In the histomorphometric analysis, the landing animals showed significantly higher bone volume ratio (BV/TV, %) and trabecular thickness (Tb. Th, μm). The effect of time was also evident in the bone tissue wet weight (WW) and fat-free dry weight (FFDW), while the landing showed no effects on the WW and the FFDW. Our study preliminarily showed that 1- and 4-week landing training was beneficial on the trabecular structure of the proximal tibia in female rats. Further study would be valuable to investigate related cellular response as well as tissue material properties of the spongy bone in free-fall landing rats.