The Effect of a Moderately-low and High Carbohydrate Intake on Crossfit Performance

International Journal of Exercise Science 9(4): 460-470, 2016. CrossFit is a metabolically demanding strength and conditioning method which performance may benefit from a carbohydrate (CHO)-rich diet. This study investigated the effect of three consecutive days of high CHO intake on CrossFit performance and corresponding metabolically -related variables in strength trained individuals. Eighteen subjects with a CHO intake of \u3c6 g/kg/day were randomly assigned into a CHO (n = 9) or control (C) group (n =9) and underwent a 9-day training protocol. During days 1, 5, and 9, performance was measured as repetitions completed during a 12 minute CrossFit workout. Oxygen consumption (VO2), respiratory exchange ratio (RER), and blood lactate (BL) were also measured. Days 6-8, the CHO group increased CHO intake from \u3c6 g/kg/day to 6-8 g/kg/day; the C group maintained their current intake of \u3c6 g/kg/day. On days 6 and 7 both groups performed CrossFit workouts followed by a day of rest prior to day 9. There was a significant increase in repetitions completed in both groups in day 9 (vs. means score of day 1 + 5) (p = 0.002), but no differences between C and CHO groups (p = 0.111). However, the CHO group displayed a 15.2 repetition increase (+10.9%) in day 9, compared to 5.7 (+4.2%) by the C group. VO2, RER, and BL were not influenced by the experimental intervention. Our results suggest that the CrossFit-embraced practice of moderately-low CHO diets may be adequate in CHO during short periods of training, however, given the noted trend, extended training periods may be effected

Influence of Sport Specialization on Athletic Performance and Injury Risk in Collegiate Swimmers

To assess the effect of swimming specialization on performance and injury risk in collegiate swimmers, thirty collegiate swimmers (20.1 ± 0.9 years [18.5 – 22.3 years]) were asked to complete an anonymous survey to provide information regarding their sports participation history, success in swimming, and the occurrence and quantity of swimming-related injuries. Specialization status was determined by the swimmer claiming they had specialized and by the number of months (≥ 8 months) they participated in swimming each year. Correlation analysis revealed several significant (p \u3c 0.05) relationships between all determinants of specialization, swimming success, and swimming injuries. Stepwise regression analysis revealed that the age which an athlete specialized was the best predictor of the occurrence of a swimming- related injury (R2 = 0.34, p = 0.004) and the number of injuries sustained (R2 = 0.25, p = 0.019). Years of competitive swimming experience was the best predictor (p \u3c 0.008) of performance in the freestyle stroke at 50-yards (R2 = 0.47), 100-yards (R2 = 0.53), and 500-yards (R2 = 0.43), the back stroke at 200-yards (R2 = 0.41), and the 100-yard butterfly (R2 = 0.55). The age in which the athlete specialized in swimming was the best predictor of the 200-yard individual medley (R2 = 0.30, p = 0.037). Our data suggests that swimming specialization may be beneficial for success in select swimming events but is not as important as years of competitive experience and may also lead to a greater number of swimming-related injuries

Time-restricted Feeding Plus Resistance Training in Active Females: A Randomized Trial

Background A very limited amount of research has examined intermittent fasting (IF) programs, such as time-restricted feeding (TRF), in active populations. Objective Our objective was to examine the effects of TRF, with or without β-hydroxy β-methylbutyrate (HMB) supplementation, during resistance training (RT). Methods This study employed a randomized, placebo-controlled, reduced factorial design and was double-blind with respect to supplementation in TRF groups. Resistance-trained females were randomly assigned to a control diet (CD), TRF, or TRF plus 3 g/d HMB (TRFHMB). TRF groups consumed all calories between 1200 h and 2000 h, whereas the CD group ate regularly from breakfast until the end of the day. All groups completed 8 wk of supervised RT and consumed supplemental whey protein. Body composition, muscular performance, dietary intake, physical activity, and physiological variables were assessed. Data were analyzed prior to unblinding using mixed models and both intention-to-treat (ITT) and per protocol (PP) frameworks. Results Forty participants were included in ITT, and 24 were included in PP. Energy and protein intake (1.6 g/kg/d) did not differ between groups despite different feeding durations (TRF and TRFHMB: ∼7.5 h/d; CD: ∼13 h/d). Comparable fat-free mass (FFM) accretion (+2% to 3% relative to baseline) and skeletal muscle hypertrophy occurred in all groups. Differential effects on fat mass (CD: +2%; TRF: −2% to −4%; TRFHMB: −4% to −7%) were statistically significant in the PP analysis, but not ITT. Muscular performance improved without differences between groups. No changes in physiological variables occurred in any group, and minimal side effects were reported. Conclusions IF, in the form of TRF, did not attenuate RT adaptations in resistance-trained females. Similar FFM accretion, skeletal muscle hypertrophy, and muscular performance improvements can be achieved with dramatically different feeding programs that contain similar energy and protein content during RT. Supplemental HMB during fasting periods of TRF did not definitively improve outcomes. This study was prospectively registered at clinicaltrials.gov as NCT03404271

The Effect of Quercetin on Bone Turnover Markers, Inflammatory Markers, and Bone Mineral Density in Postmenopausal Women: A Double-Blind Placebo-Controlled Investigation

Maintaining optimal bone health prevents major bone disorders (e.g., osteoporosis) and prolongs longevity. Quercetin is a plant-based flavonoid that is suggested to have anti-inflammatory effects and may improve bone health. PURPOSE: To investigate the effects of quercetin supplementation over 90-days on prominent bone turnover markers (BTMs), inflammatory markers, bone mineral density (BMD), body composition, and physical functioning in postmenopausal women. METHODS: Thirty-three healthy, nonosteoporotic, postmenopausal women (59.2±7.0 years) participated in a double-blind, placebo-controlled investigation. Participants were randomized into one of two supplement groups: 1) 500 mg of quercetin (QUE) once daily or 2) 500 mg of methylcellulose (placebo; PLB) once daily. Pre- and post-testing visits included assessments of BTMs (i.e., osteocalcin [OC], procollagen type-I N-terminal propeptide [PINP], and type-I collagen cross-linked C-terminal telopeptide [CTX]), inflammatory markers (i.e., interleukin [IL]-6, tumor necrosis factor-alpha [TNF-a], and C-reactive protein [CRP]), BMD measurements, body composition measurements (i.e., body fat percentage), and physical function. RESULTS: The QUE group increased OC (p=0.016; d=0.89), PINP (p=0.030; d=0.64), and CTX (p=0.023; d=0.91) levels and decreased IL-6 (p=0.045; d=0.73) and TNF-a (p=0.021; d=0.90) levels compared to PLB. CRP (p=0.448; d=0.34), BMD, body composition, and physical function remained unchanged. CONCLUSION: The results indicate that QUE may maintain optimal bone health by mediating bone formation and decreasing pro-inflammatory cytokines

Sex Differences in Plantar Flexor Strength and Contractile Properties after Isometric and Dynamic Fatigue

Purpose: To determine sex differences in strength and contractile properties after isometric and dynamic fatiguing exercise of the plantar flexors. Methods: Recreationally active males (n=13, age=22.4±2.2 yrs) and females (n=15, age=20.9±2.4 yrs) performed a maximal isometric (2 min) and isotonic (120 reps at 30% peak torque) fatigue task on 2 separate visits. Before and after each fatigue task, participants performed a 3 sec maximal voluntary isometric contraction (MVIC) with tibial nerve stimulation being delivered during and immediately after the MVIC. Peak torque (PT; highest 250 ms) was obtained during the voluntary phase of the MVIC. Peak twitch torque (TTQ), rate of torque development (RTD; Δtorque/Δtime), and half relaxation time (HRT; time for TTQto decrease from peak to 50%) were calculated from the resting twitch after the MVIC. Voluntary activation (VA%; ability of the muscle to be fully activated) was calculated using a corrected interpolated twitch formula. Three-way (condition × sex × time) repeated measures ANOVAs were used for analysis. Results: Regardless of sex or condition, TTQ(-23.1%), RTD (-12.6%), HRT (+22.9%) were changed after fatigue (p\u3c0.05), while VA% remained unchanged (p\u3e0.05). Regardless of condition, PT was more reduced in males (-22.5%) compared to females (-19.2%)(p=0.017). Conclusions: Our findings indicate that the fatigue-induced decrease in strength was greater in males than females. While our findings do not identify the contributing physiological mechanism(s), changes at the peripheral level may be responsible

Oregano (Origanum vulgare) Consumption Reduces Oxidative Stress and Markers of Muscle Damage after Combat Readiness Tests in Soldiers

Military activities often involve high-intensity exercise that can disrupt antioxidant capacity. We investigated the effects of oregano supplementation on muscle damage, oxidative stress, and plasma antioxidant markers of soldiers performing the army combat readiness test (ACRT). Twenty-four healthy male soldiers (age: 24 ± 3 years, height: 167 ± 14 cm, mass: 66 ± 3 kg) were randomized into a placebo group (n = 12) or an oregano supplementation group (n = 12). The participants consumed a capsule containing 500 mg Origanum vulgare immediately after completing the ACRT. Blood sampling was taken before exercise, immediately after exercise, and 60 and 120 min after oregano consumption. Plasma levels of creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant capacity (TAC), and glutathione peroxidase (GPX) were measured at the four time points. The time × group interactions were found for CK (p < 0.0001, d = 3.64), LDH (p < 0.0001, d = 1.64), MDA (p < 0.0001, d = 9.94), SOD (p < 0.0001, d = 1.88), TAC (p < 0.0001, d = 5.68) and GPX (p < 0.0001, d = 2.38). In all variables, the difference between placebo and oregano groups were significant at 60 (p < 0.0001) and 120 (p < 0.0001) minutes after ACRT test. The main effect of time was also significant for all the variables (p < 0.0001). Our results suggest that oregano supplementation has the potential to reduce muscle damage and increase oxidative capacity following ACRT. Supplementation with oregano may serve as a dietary strategy to increase preparedness and promote recovery in military recruits

Effects of Exercise Training on Bone Health Parameters in Individuals With Obesity:A Systematic Review and Meta-Analysis

International audienceBackground: Osteoporosis causes bone fragility, increasing the risk of fractures. Evidence suggests a strong correlation between obesity and fracture risk. Physical training is known to enhance bone resistance and protect from fracture; however, its osteogenic effect in the presence of obesity remains unknown.and nbsp;Objective: We sought to evaluate the influence of exercise training on bone health indices in individuals with obesity.and nbsp;Methods: This systematic literature search was conducted using common electronic databases from inception - December 2019. The following key terms (and synonyms searched for by the MeSH database) were included and combined using the operators &quot;AND, &quot; &quot;OR, &quot; &quot;NOT &quot;: [( &quot;body mass index &quot; OR obesity OR obese OR overweight OR fat mass) AND ( &quot;bone mineral density &quot; OR &quot;bone mineral content &quot; OR &quot;peak bone mass &quot; OR &quot;mechanical loading &quot; OR &quot;Osteoporosis &quot; OR &quot;bone geometry &quot; OR &quot;bone resistance &quot;) AND ( &quot;exercise training &quot; OR &quot;physical training &quot; OR &quot;strength training, &quot; OR &quot;resistance training &quot; OR &quot;aerobic training &quot; OR &quot;combined training &quot;)].and nbsp;Results: After screening, 10 studies (889 initial records) were included in the final analysis (8 different countries, 263 participants). Two studies investigated males, six females, and two, both sexes. The training duration was at least eight weeks with 2-3 sessions/week. Physical training displayed a significant trivial impact on the whole body (WB) BMD (0.13 SMD; 95% CI [0.00, 0.26], p = 0.046). Subgroup analyses indicated a significant small increase in the WB BMD (0.27 SMD; 95% CI [0.00, 0.53], p = 0.048) in the endurance training group, a non-significant trivial increase in the WB BMD (0.11 SMD; 95% CI [-0.06, 0.29], p = 0.203) in the resistance group, and a non-significant trivial increase in the WB BMD (0.03 SMD; 95% CI [-0.26, 0.32], p = 0.86) in the combined training group. In addition, a significant small decrease was found in the weight of trained subjects (-0.24 SMD; 95% CI [-0.42, -0.05], p = 0.011).and nbsp;Conclusion: Physical training has little to no effect on the WB BMD in subjects with overweight/obesity. Currently, insufficient evidence to advocate for any specific type of exercise for enhancing bone health exists for overweight/obese individuals. Investigations examining the impact of varying types of physical exercise on WB BMD of obese individuals are needed

Effect of Branched-Chain Amino Acid Supplementation on Recovery Following Acute Eccentric Exercise

This study investigated the effect of branched-chain amino acid (BCAA) supplementation on recovery from eccentric exercise. Twenty males ingested either a BCAA supplement or placebo (PLCB) prior to and following eccentric exercise. Creatine kinase (CK), vertical jump (VJ), maximal voluntary isometric contraction (MVIC), jump squat (JS) and perceived soreness were assessed. No significant (p \u3e 0.05) group by time interaction effects were observed for CK, soreness, MVIC, VJ, or JS. CK concentrations were elevated above baseline (p \u3c 0.001) in both groups at 4, 24, 48 and 72 hr, while CK was lower (p = 0.02) in the BCAA group at 48 hr compared to PLCB. Soreness increased significantly from baseline (p \u3c 0.01) in both groups at all time-points; however, BCAA supplemented individuals reported less soreness (p \u3c 0.01) at the 48 and 72 hr time-points. MVIC force output returned to baseline levels (p \u3e 0.05) at 24, 48 and 72 hr for BCAA individuals. No significant difference between groups (p \u3e 0.05) was detected for VJ or JS. BCAA supplementation may mitigate muscle soreness following muscle-damaging exercise. However, when consumed with a diet consisting of ~1.2 g/kg/day protein, the attenuation of muscular performance decrements or corresponding plasma CK levels are likely negligible

Effect of Intensity on Changes in Cardiac Autonomic Control of Heart Rate and Arterial Stiffness After Equated Continuous Running Training Programs

[EN] Background: It is well known that exercise training has positive effects on both cardiac autonomic function and arterial stiffness (AS). However, it is not clear that which exercise training variables, intensity or volume, or both, play a crucial role in this regard. This study investigates the chronic effects of high-volume moderate-intensity training (HVMIT) and low-volume high-intensity training (LVHIT) on heart rate variability (HRV) and AS in sedentary adult men. Materials and Methods: Notably, 45 males (age: 42 ± 5.7 years) were randomly assigned to a control (n = 15), HVMIT (n = 15), or LVHIT (n = 15). The HVMIT group ran three times per week on a treadmill at 50–60% of VO2max for 45–60 min, while the LVHIT trained at 70–85% of VO2max for 25–40 min. Both training protocols were equated by caloric expenditure. HRV, pulse wave velocity (PWV), hemodynamic variables, and body composition were measured before and after 12 weeks. Results: Both protocols (i.e., HVMIT and LVHIT) significantly increased the SD of normal sinus beat intervals (SDNN) and high-frequency (HF) bands (p < 0.05) after 12 weeks. Whereas the low-frequency (LF)-HF ratio decreased significantly in both training protocols (p < 0.05); however, these changes were significantly greater in the LVHIT protocol (p < 0.05). Furthermore, the root mean square of successive RR interval differences (RMSSD) significantly increased only in the LVHIT (p < 0.05). Moreover, a significant decrease in LF and PWV was only observed following the LVHIT protocol (p < 0.05). Some measures of HRV and PWV were significantly correlated (r = 0.275–0.559; p < 0.05). Conclusion: These results show that the LVHIT protocol was more efficient for improving HRV variables and PWV than the HVMIT protocol after 12 weeks of continuous running training. Interestingly, changes in some HRV parameters were related to changes in PWV. Further studies should elaborate on the link between central and peripheral cardiovascular adaptations after continuous and intermittent training regimens differing in intensity

Reply to “Programming may matter most.” Response to “Metabolic effects of two high-intensity circuit training protocols: Does sequence matter?”

We appreciate the interest that our study elicited and the comments from a reader. We commend the reader of our paper for critically evaluating the protocol and results of the study. Here, we would like to respond to the statement made in the letter. Indeed, the rest intervals were longer and time at VO2max was lower in our study than recommended by Bucheit and Larsen.1 However, because the reader is interested in the practical implications of our study, we ask that they consider the following