Comparison of whole egg v. egg white ingestion during 12 weeks of resistance training on skeletal muscle regulatory markers in resistance-trained men.

Eggs are considered a high-quality protein source for their complete amino acid profile and digestibility. Therefore, this study aimed to compare the effects of whole egg (WE) v. egg white (EW) ingestion during 12 weeks of resistance training (RT) on the skeletal muscle regulatory markers and body composition in resistance-trained men. Thirty resistance-trained men (mean age 24·6 (sd 2·7) years) were randomly assigned into the WE + RT (WER, n 15) or EW + RT (EWR, n 15) group. The WER group ingested three WE, while the EWR group ingested an isonitrogenous quantity of six EW per d immediately after the RT session. Serum concentrations of regulatory markers and body composition were measured at baseline and after 12 weeks. Significant main effects of time were observed for body weight (WER 1·7, EWR 1·8 kg), skeletal muscle mass (WER 2·9, EWR 2·7 kg), fibroblast growth factor-2 (WER 116·1, EWR 83·2 pg/ml) and follistatin (WER 0·05, EWR 0·04 ng/ml), which significantly increased (P < 0·05), and for fat mass (WER -1·9, EWR -1·1 kg), transforming growth factor-ß1 (WER -0·5, EWR -0·1 ng/ml), activin A (WER -6·2, EWR -4·5 pg/ml) and myostatin (WER -0·1, EWR -0·06 ng/ml), which significantly decreased (P < 0·05) in both WER and EWR groups. The consumption of eggs absent of yolk during chronic RT resulted in similar body composition and functional outcomes as WE of equal protein value. EW or WE may be used interchangeably for the dietary support of RT-induced muscular hypertrophy when protein intake is maintained.

The Effects of Multi-Day vs. Single Pre-exercise Nitrate Supplement Dosing on Simulated Cycling Time Trial Performance and Skeletal Muscle Oxygenation.

Jo, E, Fischer, M, Auslander, AT, Beigarten, A, Daggy, B, Hansen, K, Kessler, L, Osmond, A, Wang, H, and Wes, R. The effects of multiday vs. single pre-exercise nitrate supplement dosing on simulated cycling time trial performance and skeletal muscle oxygenation. J Strength Cond Res 33(1): 217-224, 2019-A transient augmentation in the metabolic efficiency of skeletal muscle is the purported basis for dietary nitrate supplementation amongst competitive and recreational athletes alike. Previous studies support the ergogenic effects of nitrate supplementation, as findings indicated improved microvascular blood flow, exercise economy, and performance with relatively short-term supplementation. As with most ergogenic aids, the optimum duration of supplementation before performance or competition, i.e., loading phase, is a critical determinant for efficacy. Therefore, the purpose of this study was to investigate the effects of long-term vs. single dosing nitrate supplementation on skeletal muscle oxygenation and cycling performance. In a randomized, placebo controlled, double blind, parallel design study, healthy, recreationally active men (n = 15) and women (n = 14) subjects (age = 18-29 years) completed an 8 km (5 mi) simulated cycling time trial before and after a 14-day supplementation period with either a nitrate supplement (Multi-Day Dosing Group) (n = 14) or placebo (Single Pre-Exercise Dosing Group; SD) (n = 15). Both groups consumed a single dose of the nitrate supplement 2 hours before the post-treatment time trial. In addition, skeletal muscle oxygenation was measured via near-infrared spectroscopy during each time trial. Multiday nitrate supplementation significantly decreased time to completion (p = 0.01) and increased average power (p = 0.04) and speed (p = 0.02) from pre-to post-treatment, while a single dosing produced no significant changes to these measures. There were no significant differences over time and across treatments for any other measures including muscle oxygenation variables. Overall, long-term nitrate supplementation appears to have an advantage over a single pre-exercise dosing on cycling performance and metabolic efficiency as indicated by an increase in power output with no change in oxygenation.

Muscle health and performance in monozygotic twins with 30 years of discordant exercise habits.

INTRODUCTION: Physical health and function depend upon both genetic inheritance and environmental factors (e.g., exercise training). PURPOSE: To enhance the understanding of heritability/adaptability, we explored the skeletal muscle health and physiological performance of monozygotic (MZ) twins with > 30 years of chronic endurance training vs. no specific/consistent exercise. METHODS: One pair of male MZ twins (age = 52 years; Trained Twin, TT; Untrained Twin, UT) underwent analyses of: (1) anthropometric characteristics and blood profiles, (2) markers of cardiovascular and pulmonary health, and (3) skeletal muscle size, strength, and power and molecular markers of muscle health. RESULTS: This case study represents the most comprehensive physiological comparison of MZ twins with this length and magnitude of differing exercise history. TT exhibited: (1) lower body mass, body fat%, resting heart rate, blood pressure, cholesterol, triglycerides, and plasma glucose, (2) greater relative cycling power, anaerobic endurance, and aerobic capacity (VO2max), but lower muscle size/strength and poorer muscle quality, (3) more MHC I (slow-twitch) and fewer MHC IIa (fast-twitch) fibers, (4) greater AMPK protein expression, and (5) greater PAX7, IGF1Ec, IGF1Ea, and FN14 mRNA expression than UT. CONCLUSIONS: Several measured differences are the largest reported between MZ twins (TT expressed 55% more MHC I fibers, 12.4 ml/kg/min greater VO2max, and 8.6% lower body fat% vs. UT). These data collectively (a) support utilizing chronic endurance training to improve body composition and cardiovascular health and (b) suggest the cardiovascular and skeletal muscle systems exhibit greater plasticity than previously thought, further highlighting the importance of studying MZ twins with large (long-term) differences in exposomes.

Effect of conjugated linoleic acids and omega-3 fatty acids with or without resistance training on muscle mass in high-fat diet-fed middle-aged mice.

NEW FINDINGS: What is the central question of this study? This study examined the effects of 20 weeks of administration of conjugated linoleic acids/omega-3 fatty acids with or without programed resistance exercise training on body composition, skeletal muscle properties and functional capacity in middle-aged mice fed a high-fat diet. What is the main finding and its importance? Chronic daily administration of conjugated linoleic acids/omega-3 fatty acids with resistance exercise training can help to blunt fat gain, alleviate loss of myogenic capacity and sensorimotor function and lower tissue inflammation in middle-aged mice during chronic high-fat diet-induced catabolism. This study investigated the effects of 20 weeks of combined conjugated linoleic acid (CLA)/omega-3 fatty acid (n-3) administration independently or combined with resistance exercise training (RET) on skeletal muscle in middle-aged mice consuming a high-fat diet (HFD). Nine-month-old C57BL/6 mice were randomly assigned into four experimental groups (H, high-fat diet; HE, H + RET; HCN, H + CLA/n-3; and HECN, H + CLA/n3 + RET). Body composition and functional capacity were assessed pre- and post-intervention. Muscle tissues were collected at 14 months of age. ANOVA was used, with significance set at P ≤ 0.05. Fat mass significantly increased in H (+74%), HE (+142%) and HECN (+43%) but not in HCN. Muscle wet weights were significantly lower in H and HCN than in HE and HECN. Grip strength substantially declined in H (-15%) and HCN (-17%), whereas sensorimotor function significantly declined only in H (-11%). HECN exhibited improvement in strength (+22%) and sensorimotor coordination (+17%). In comparison to H, muscle tumour necrosis factor-α mRNA expression was significantly lower in HE (-39%), HCN (-24%) and HECN (-21%), respectively. Mean myofibre cross-sectional areas were markedly lower in H and HCN than in HE and HECN. H showed significantly lower satellite cell abundance and numbers of myonuclei than all other groups. Our findings suggest that long-term daily CLA/n-3 intake with resistance training improved sensorimotor function, ameliorated fat gain and prevented loss of myogenic capacity while lowering tumour necrosis factor-α expression during chronic HFD.

Dietary Caffeine and Polyphenol Supplementation Enhances Overall Metabolic Rate and Lipid Oxidation at Rest and After a Bout of Sprint Interval Exercise.

Jo, E, Lewis, KL, Higuera, D, Hernandez, J, Osmond, AD, Directo, DJ, and Wong, M. Dietary caffeine and polyphenol supplementation enhances overall metabolic rate and lipid oxidation at rest and after a bout of sprint interval exercise. J Strength Cond Res 30(7): 1871-1879, 2016-The purpose of this study was to investigate the effects of a caffeine-polyphenolic supplement on (a) metabolic rate and fat oxidation at rest and after a bout of sprint interval exercise (SIE) and (b) SIE performance. In a double-blind, randomized, placebo-controlled, crossover study and after an initial familiarization visit, 12 subjects (male: n = 11; female: n = 1) (body mass = 76.1 ± 2.2 kg; height = 169.8 ± 1.6 cm; body mass index = 22.7 ± 3.0 kg·m; body fat % = 21.6 ± 2.0%) underwent 2 testing sessions during which time they consumed either a caffeine-polyphenol supplement or placebo. After supplementation, resting energy expenditure, heart rate (HR), and blood pressure (BP) were assessed. Subsequently, subjects performed 30 minutes of SIE while researchers collected performance data. Subjects were then tested for post-SIE energy expenditure, HR, and BP. The caffeine-polyphenol treatment resulted in significantly (p ≤ 0.05) greater energy expenditure (+7.99% rest; +10.16% post-SIE), V[Combining Dot Above]O2 (+9.64% rest; +12.10% post-SIE), and fat oxidation rate (+10.60% rest; +9.76% post-SIE) vs. placebo at rest and post-SIE. No significant differences were detected for peak and average power at all sprint intervals between treatments. Post-SIE HR was significantly (p ≤ 0.05) greater with caffeine-polyphenol supplementation vs. placebo (90.8 ± 3.5 vs. 85.1 ± 3.6 b·min). There were no significant between-treatment differences for BP. It may be concluded that the observed thermogenic response after SIE was directly attributable to caffeine-polyphenol supplementation as opposed to an indirect manifestation of enhanced performance and work output. Collectively, these results corroborate the use of dietary caffeine and polyphenols to support efforts to reduce adiposity and improve overall body composition especially in conjunction with SIE.

Modified Daily Undulating Periodization Model Produces Greater Performance Than a Traditional Configuration in Powerlifters.

The primary aim of this study was to compare 2 daily undulating periodization (DUP) models on one-repetition maximum (1RM) strength in the squat, bench press, deadlift, total volume (TV) lifted, and temporal hormone response. Eighteen male, college-aged (21.1 ± 1.9 years) powerlifters participated in this study and were assigned to one of 2 groups: (a) traditional DUP training with a weekly training order: hypertrophy-specific, strength-specific, and power-specific training (HSP, n = 9) or (b) modified DUP training with a weekly training order: hypertrophy-specific, power-specific, and strength-specific training (HPS, n = 9). Both groups trained 3 nonconsecutive days per week for 6 weeks and performed the squat, bench press, and deadlift exercises. During hypertrophy and power sessions, subjects performed a fixed number of sets and repetitions but performed repetitions until failure at a given percentage during strength sessions to compare TV. Testosterone and cortisol were measured at pretesting and posttesting and before each strength-specific day. Hypertrophy, power, and strength produced greater TV in squat and bench press (p ≤ 0.05) than HSP, but not for deadlift (p > 0.05). For squat and deadlift, there was no difference between groups for 1RM (p > 0.05); however, HPS exhibited greater increases in 1RM bench press than HSP (p ≤ 0.05). Effect sizes (ES) showed meaningful differences (ES > 0.50) in favor of HPS for squat and bench press 1RM. Testosterone decreased (p ≤ 0.05) at weeks 5 and 6 and cortisol decline at weeks 3 and 4. However, neither hormone was different at posttesting compared with pretesting (p > 0.05). Our findings suggest that an HPS configuration of DUP has enhanced performance benefits compared with HSP.

Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve.

The primary aim of this study was to compare rating of perceived exertion (RPE) values measuring repetitions in reserve (RIR) at particular intensities of 1 repetition maximum (RM) in experienced (ES) and novice squatters (NS). Furthermore, this investigation compared average velocity between ES and NS at the same intensities. Twenty-nine individuals (24.0 ± 3.4 years) performed a 1RM squat followed by a single repetition with loads corresponding to 60, 75, and 90% of 1RM and an 8-repetition set at 70% 1RM. Average velocity was recorded at 60, 75, and 90% 1RM and on the first and last repetitions of the 8-repetition set. Subjects reported an RPE value that corresponded to an RIR value (RPE-10 = 0-RIR, RPE-9 = 1-RIR, and so forth). Subjects were assigned to one of the 2 groups: (a) ES (n = 15, training age: 5.2 ± 3.5 years) and (b) NS (n = 14, training age: 0.4 ± 0.6 years). The mean of the average velocities for ES was slower (p ≤ 0.05) than NS at 100% and 90% 1RM. However, there were no differences (p > 0.05) between groups at 60, 75%, or for the first and eighth repetitions at 70% 1RM. In addition, ES recorded greater RPE at 1RM than NS (p = 0.023). In ES, there was a strong inverse relationship between average velocity and RPE at all percentages (r = -0.88, p < 0.001), and a strong inverse correlation in NS between average velocity and RPE at all intensities (r = -0.77, p = 0.001). Our findings demonstrate an inverse relationship between average velocity and RPE/RIR. Experienced squatter group exhibited slower average velocity and higher RPE at 1RM than NS, signaling greater efficiency at high intensities. The RIR-based RPE scale is a practical method to regulate daily training load and provide feedback during a 1RM test.

Validation of Biofeedback Wearables for Photoplethysmographic Heart Rate Tracking.

The purpose of this study was to examine the validity of HR measurements by two commercial-use activity trackers in comparison to ECG. Twenty-four healthy participants underwent the same 77-minute protocol during a single visit. Each participant completed an initial rest period of 15 minutes followed by 5 minute periods of each of the following activities: 60W and 120W cycling, walking, jogging, running, resisted arm raises, resisted lunges, and isometric plank. In between each exercise task was a 5-minute rest period. Each subject wore a Basis Peak (BPk) on one wrist and a Fitbit Charge HR (FB) on the opposite wrist. Criterion measurement of HR was administered by 12-lead ECG. Time synced data from each device and ECG were concurrently and electronically acquired throughout the entire 77-minute protocol. When examining data in aggregate, there was a strong correlation between BPk and ECG for HR (r = 0.92, p < 0.001) with a mean bias of -2.5 bpm (95% LoA 19.3, -24.4). The FB demonstrated a moderately strong correlation with ECG for HR (r = 0.83, p < 0.001) with an average mean bias of -8.8 bpm (95% LoA 24.2, -41.8). During physical efforts eliciting ECG HR > 116 bpm, the BPk demonstrated an r = 0.77 and mean bias = -4.9 bpm (95% LoA 21.3, -31.0) while the FB demonstrated an r = 0.58 and mean bias = -12.7 bpm (95% LoA 28.6, -54.0). The BPk satisfied validity criteria for HR monitors, however showed a marginal decline in accuracy with increasing physical effort (ECG HR > 116 bpm). The FB failed to satisfy validity criteria and demonstrated a substantial decrease in accuracy during higher exercise intensities.

Effects of chronic high-fat feeding on skeletal muscle mass and function in middle-aged mice.

BACKGROUND AND AIMS: Increased adipose tissue may promote catabolic events in skeletal muscle. The aim of this study was to test whether high-fat diet (HFD)-induced obesity would accelerate the onset of muscle wasting in middle-aged mice. METHODS: Muscle was collected from C57BL/6 mice at 9 months of age (baseline) and 14 months of age after consuming a control (C) or HFD. Mice in C and HFD were also subjected to evaluations of body composition and function before and after their respective diets. RESULTS: HFD demonstrated significant (p < 0.05) losses of grip strength (-15 %) and sensorimotor coordination (-11 %), whereas C did not. Lean mass decreased to a greater degree in HFD although not significantly (C: -20.69 ± 7.94 vs. HFD: -31.14 ± 5.49 %, p > 0.05). Gastrocnemius, quadriceps, and hamstrings mass in C and HFD were significantly reduced from baseline (-27 to 43 and -39 to 47 %, respectively, p < 0.05) with no differences between the two; however, soleus mass was lower only in HFD (-24 %, p = 0.03). Myofiber area, satellite cells, and myonuclei of the gastrocnemius were lower only in HFD (-23, -19, and -16 %, respectively, p < 0.05) compared to baseline. CONCLUSIONS: HFD-induced obesity adversely affected function in middle-aged mice. Atrophy of the soleus in HFD but not C suggests sensitivity of oxidative muscle to HFD-dependent catabolism more so than aging. In the muscles containing fast/mixed fibers, aging effects may have concealed the catabolic nature of HFD; however, morphological changes in the gastrocnemius including decreased fiber area, satellite cells, and myonuclei are consistent with an atrophic phenotype related to HFD.

Repeated Bout Effect in Muscle-Specific Exercise Variations.

A single bout of unaccustomed exercise confers protective effect against muscle damage from a subsequent bout of similar activity, that is, repeated bout effect (RBE). It remains unknown whether varying muscle-specific exercise between sessions alters the magnitude of the RBE. This study examined the effects of muscle-specific exercise variation between consecutive sessions on the RBE. Twenty untrained males (21 ± 2 years) were assigned to one of 2 groups (n = 10 per group): (a) 2 sessions of incline curls, Fixed Exercise or (b) 1 session of incline curls followed by 1 session of preacher curls, Varied Exercise, with 7 days between sessions. Subjects performed 5 sets of 6 repetitions at ∼50% of maximal isometric elbow flexor strength during each session. Changes in maximal voluntary isometric and isokinetic torque, range of motion, muscle soreness, and serum creatine kinase were measured before, immediately after, and 24, 48, 72, and 96 hours after each exercise session, and the changes were compared between bouts and between groups. There were significant time effects (p < 0.05) for isometric maximal voluntary contraction, concentric maximal voluntary contraction, range of motion, and muscle soreness during sessions 1 and 2 with no between-group differences. Both groups demonstrated a significantly faster recovery of range of motion and soreness to baseline levels after session 2 compared with session 1. Overall, our findings suggest that incline curls conferred a protective effect during subsequent preacher curls in a similar way to repeating incline curls; therefore, the RBE was not exercise specific.

Influence of physical activity and nutrition on obesity-related immune function.

Research examining immune function during obesity suggests that excessive adiposity is linked to impaired immune responses leading to pathology. The deleterious effects of obesity on immunity have been associated with the systemic proinflammatory profile generated by the secretory molecules derived from adipose cells. These include inflammatory peptides, such as TNF- α , CRP, and IL-6. Consequently, obesity is now characterized as a state of chronic low-grade systemic inflammation, a condition considerably linked to the development of comorbidity. Given the critical role of adipose tissue in the inflammatory process, especially in obese individuals, it becomes an important clinical objective to identify lifestyle factors that may affect the obesity-immune system relationship. For instance, stress, physical activity, and nutrition have each shown to be a significant lifestyle factor influencing the inflammatory profile associated with the state of obesity. Therefore, the purpose of this review is to comprehensively evaluate the impact of lifestyle factors, in particular psychological stress, physical activity, and nutrition, on obesity-related immune function with specific focus on inflammation.

Meta-analysis of postactivation potentiation and power: effects of conditioning activity, volume, gender, rest periods, and training status.

There is no clear agreement regarding the ideal combination of factors needed to optimize postactivation potentiation (PAP) after a conditioning activity. Therefore, a meta-analysis was conducted to evaluate the effects of training status, volume, rest period length, conditioning activity, and gender on power augmentation due to PAP. A total of 141 effect sizes (ESs) for muscular power were obtained from a total of 32 primary studies, which met our criteria of investigating the effects of a heavy preconditioning activity on power in randomized human trials. The mean overall ES for muscle power was 0.38 after a conditioning activity (p < 0.05). Significant differences were found between moderate intensity (60-84%) 1.06 and heavy intensity (>85%) 0.31 (p < 0.05). There were overall significant differences found between single sets 0.24 and multiple sets 0.66 (p < 0.05). Rest periods of 7-10 minutes (0.7) after a conditioning activity resulted in greater ES than 3-7 minutes (0.54), which was greater than rest periods of >10 minutes (0.02) (p < 0.05). Significant differences were found between untrained 0.14 and athletes 0.81 and between trained 0.29 and athletes. The primary findings of this study were that a conditioning activity augmented power output, and these effects increased with training experience, but did not differ significantly between genders. Moreover, potentiation was optimal after multiple (vs. single) sets, performed at moderate intensities, and using moderate rest periods lengths (7-10 minutes).

Potential mechanisms underlying the role of chronic inflammation in age-related muscle wasting.

Sarcopenia, an age-related condition characterized by progressive skeletal muscle degeneration, might exist as one of the primary clinical conditions underlying severe functional impairment as well as increased risk of co-morbidities in the elderly. Although the etiology of sarcopenia remains multifaceted, age-related chronic inflammation has been strongly implicated in muscle wasting and related sequelae during advanced age. Recent evidence suggests that aberrant, unresolved alterations in regular inflammatory processes during advanced age might ultimately operate as the link that drives skeletal muscle to become more degenerative and dysfunctional in nature. Such negative atrophic muscular outcomes might result from inflammation-induced disruption of central mechanisms regulating skeletal muscle morphology and remodeling. In addition, recent findings demonstrate an adverse confluence between sarcopenia and excessive adiposity (i.e. sarcopenic obesity), as the co-existence of such adverse alterations in body composition may exacerbate systemic inflammation and muscle wasting in the elderly. The following evidence-based review serves to examine sarcopenia from a mechanistic perspective with emphasis on chronic inflammation.

The effects of endurance, strength, and power training on muscle fiber type shifting.

Muscle fibers are generally fractionated into type I, IIA, and IIX fibers. Type I fibers specialize in long duration contractile activities and are found in abundance in elite endurance athletes. Conversely type IIA and IIX fibers facilitate short-duration anaerobic activities and are proportionally higher in elite strength and power athletes. A central area of interest concerns the capacity of training to increase or decrease fiber types to enhance high-performance activities. Although interconversions between type IIA and IIX are well recognized in the literature, there are conflicting studies regarding the capacity of type I and II fibers to interconvert. Therefore, the purpose of this article is to analyze the effects of various forms of exercise on type I and type II interconversions. Possible variables that may increase type II fibers and decrease type I fibers are discussed, and these include high velocity isokinetic contractions; ballistic movements such as bench press throws and sprints. Conversely, a shift from type II to type I fibers may occur under longer duration, higher volume endurance type events. Special care is taken to provide practical applications for both the scientist and the athlete.

Electromyographic Examination of Hip and Knee Extension Hex Bar Exercises Varied by Starting Knee and Torso Angles.

Variations of the deadlift can be executed using the hexagonal (hex) bar by altering, for instance, the knee and torso angles while maintaining a constant hip angle at the start position. PURPOSE: To examine muscle activation patterns of the biceps femoris, rectus femoris, and erector spinae during three deadlift variations using the hex bar. METHODS: Twenty resistance-trained male and female subjects performed hex bar deadlift variations in three different starting knee flexion positions: 128.4 ± 8.5°, 111.9 ± 8.7°, and 98.3 ± 6.5°. Subjects performed three repetitions at 75% of their three-repetition maximum. Electromyography sensors were placed on the dominant biceps femoris, rectus femoris, and lumbar erector spinae. A one-way repeated measures ANOVA was used to detect differences in mean and peak EMG values normalized to maximum voluntary isometric contraction (MVIC) (p < 0.05). RESULTS: As knee flexion increased at the starting position, mean activation of the rectus femoris increased (24.7 ± 21.5 → 35.5 ± 25.4 → 62.1 ± 31.3% MVIC, p < 0.001), while biceps femoris (40.6 ± 17.9 → 34.0 ± 16.4 → 28.1 ± 14.5% MVIC, p = 0.003) and erector spinae (73.0 ± 27.6 → 65.9 ± 34.4 → 54.9 ± 32.5% MVIC, p = 0.009) activation decreased. Peak activation of the rectus femoris increased (46.9 ± 33.0 → 60.9 ± 38.7 → 99.3 ± 41.6% MVIC, p < 0.001) while decreasing in the erector spinae (118.6 ± 47.1 → 105.9 ± 49.4 → 89.1 ± 40.1% MVIC, p = 0.008). The rectus femoris experienced the greatest mean differences of the three muscles. CONCLUSIONS: Practitioners should consider the muscular goals when adjusting the starting position of a hex bar deadlift as posterior chain recruitment diminished and quadriceps activation increased as knee flexion increased.

The Effects of 10-Day Exogenous Ketone Consumption on Repeated Time Trial Running Performances: A Randomized-Control Trial.

INTRODUCTION: The effects of ketone salt supplementation on repeated short-distance running time trial (TT) performance in well-trained subjects remain unknown. PURPOSE: To determine the effects of 10-day exogenous ketone salt supplementation on two consecutive 800 m running TTs in endurance-trained subjects. METHODS: Male and female subjects were randomly allocated to one of the following groups: Ketone (KET) (n = 16) or placebo (CON) (n = 16) (8 m, 8f per group). Subjects underwent two consecutive 800 m TTs before and after a 10-day treatment on a self-propelled treadmill. Time-to-completion of the first (TT1) and second (TT2) TT, the average time-to-completion (TTAVG), and blood lactate response during each TT was measured pre-post-treatment. Changes in blood ketone levels in response to a single dosing were measured pre- and post-treatment. Data was analyzed with a mixed factorial ANOVA with significance set to p < 0.05. RESULTS: KET demonstrated a faster TTAVG from pre- to post-treatment (-6.1 ± 8.9 s; p = 0.02) while CON showed no change. At pre- and post-treatment, CON showed no acute changes in blood ketones after a single-dosing while KET demonstrated a significant increases (Pretreatment = +0.4 ± 0.3 mmol/L; p < 0.001; Post-Treatment = +0.4 ± 0.4 mmol/L; p < 0.001). These acute single-dosing responses in blood ketone levels for KET did not change between pre- and post-treatment. There were no interactions for blood lactate response to exercise or fatigue index. CONCLUSIONS: In trained subjects, 10 days of ketone salt supplementation does not affect performance in an initial bout of short-distance running, such as during TT1. However, ergogenic effects may be observed under fatigue conditions for example during a repeated running bout.

Evidence for Involvement of GIP and GLP-1 Receptors and the Gut-Gonadal Axis in Regulating Female Reproductive Function in Mice.

Substantial evidence suggests crosstalk between reproductive and gut-axis but mechanisms linking metabolism and reproduction are still unclear. The present study evaluated the possible role of glucose-dependent-insulinotropic-polypeptide (GIP) and glucagon-like-peptide-1 (GLP-1) in reproductive function by examining receptor distribution and the effects of global GIPR and GLP-1R deletion on estrous cycling and reproductive outcomes in mice. GIPR and GLP-1R gene expression were readily detected by PCR in female reproductive tissues including pituitary, ovaries and uterine horn. Protein expression was confirmed with histological visualisation of incretin receptors using GIPR-Cre and GLP1R-Cre mice in which the incretin receptor expressing cells were fluorescently tagged. Functional studies revealed that female GIPR-/- and GLP-1R-/- null mice exhibited significantly (p < 0.05 and p < 0.01) deranged estrous cycling compared to wild-type controls, indicative of reduced fertility. Furthermore, only 50% and 16% of female GIPR-/- and GLP-1R-/- mice, respectively produced litters with wild-type males across three breeding cycles. Consistent with a physiological role of incretin receptors in pregnancy outcome, litter size was significantly (p < 0.001-p < 0.05) decreased in GIPR-/- and GLP-1R-/- mice. Treatment with oral metformin (300 mg/kg body-weight), an agent used clinically for treatment of PCOS, for a further two breeding periods showed no amelioration of pregnancy outcome except that litter size in the GIPR-/- group was approximately 2 times greater in the second breeding cycle. These data highlight the significance of incretin receptors in modulation of female reproductive function which may provide future targets for pharmacological intervention in reproductive disorders.

Influence of recovery duration after a potentiating stimulus on muscular power in recreationally trained individuals.

Research examining postactivation potentiation (PAP) in recreationally trained individuals (RTI) shows mixed results. Because the balance of PAP and fatigue after heavy-load exercise influences performance outcomes, recovery duration after the stimulus might explain inconsistent results noted in RTI. The purpose of this study was to investigate the effect of recovery duration after a potentiating stimulus on muscular power in RTI. Twelve healthy RTI males (age = 23 +/- 1 yr, height = 174.6 +/- 2.5 cm, mass = 86.3 +/- 6.6 kg, 1 repetition maximum [1RM]:mass = 1.4 +/- 0.1, body fat = 15.1 +/- 2.5 %) minimally possessing 1 year of back squat experience participated. A control session assessed baseline measures on a 30-second Wingate Test. During experimental sessions, subjects performed a back squat exercise (1 set of 5 repetitions at 85% 1RM), rested for 5, 10, 15, or 20 minutes, and performed the Wingate Test. No significant differences existed among control and experimental conditions in all outcome variables; however, maximal values (regardless of rest duration) for absolute peak power (APpwr) (+7.1%), relative peak power (RPpwr) (+7.1%), and fatigue index (FI) (+8.9%) significantly differed from respective control values. The rest duration eliciting maximal PAP significantly correlated (r = -0.771) with relative 1RM. Although recovery duration failed to influence performance after a heavy-load exercise in RTI, discrepancies in individual strength might have influenced the time subjects potentiated. These results suggest stronger subjects might potentiate with less rest after a stimulus (5-10 min), whereas weaker subjects require longer rest durations (15-20 min).