Greggory R. Davis

Effect of 12 Weeks of Periodized Resistance Training Upon Total Plasma Adiponectin Concentration in Healthy Young Men.

Abstract Davis, GR, Stephens, JM, and Nelson, AG. Effect of 12 weeks of periodized resistance training upon total plasma adiponectin concentration in healthy young men. J Strength Cond Res 29(11): 3097–3104, 2015—The effects of resistance training on adiponectin have thus far yielded equivocal results. However, the effect of periodized resistance training on plasma adiponectin in offspring of type 2 diabetic and nondiabetic (ND) parents (first-degree family history) has yet to be determined. Untrained healthy young men with and without a first-degree family history of type 2 diabetes were assigned to an exercise intervention group (E) or an active control group (C). The E group performed a 12-week periodized resistance training program, whereas the C group did not participate in any structured exercise program. Fasting plasma samples were obtained pre- and posttraining. Total plasma adiponectin changed significantly in the E group (33.7 ± 14.7%, p = 0.025) but not in the C group (10.8 ± 19.2%). Offspring of type 2 diabetic parents subjects had significantly greater improvements in plasma adiponectin (69.3 ± 34.8%) compared with ND subjects (−3.2 ± 29.9%, p = 0.046). Regular aerobic exercise was significantly correlated with average plasma adiponectin (r = 0.32), whereas first-degree family history of type 2 diabetes (r = −0.58) and decreases in body fat percentage (r = −0.77) were inversely correlated with average plasma adiponectin. Periodized high-intensity resistance training seems to increase plasma adiponectin, particularly in individuals with a first-degree family history of type 2 diabetes or those who experience a significant loss of fat mass. The direct correlation between regular aerobic exercise and adiponectin further suggests that a combination of aerobic and resistance training yields greater improvements in plasma adiponectin compared with resistance training alone.

Prolonged sleep deprivation and continuous exercise: effects on melatonin, tympanic temperature, and cognitive function.

The purpose of this study was to examine tympanic temperature, melatonin, and cognitive function during a 36-hour endurance event. Nine male and three female participants took part in a 36-hour sustained endurance event without sleep (N = 12, mean age = 31.8 ± 5.0 yrs). Participants were stopped for data collection at checkpoints throughout the 36-hour event. Tympanic temperature was assessed, a psychomotor vigilance test (PVT) was administered, and saliva samples were collected. Salivary melatonin was determined via immunoassay. During the 36 hours of competition, melatonin levels were negatively correlated with the day of the race (rs = −0.277, P = 0.039) and positively associated with nighttime (rs = 0.316, P = 0.021). Significant main effects of tympanic temperature (P < 0.001), day of the competition (P = 0.018), and a tympanic temperature ∗ day of competition interaction (P < 0.001) were used to predict minor lapses in attention. No associations between melatonin levels and cognitive function were observed (P > 0.05). During the event tympanic temperature declined and was associated with an increase in lapses in attention. With sustained endurance events becoming more popular future research is warranted to evaluate the physiological impact of participation.

Relationship between family history of type 2 diabetes and serum FGF21

Determining predictive markers for the development of type 2 diabetes (T2D), particularly in young individuals, offers immense potential benefits in preventative medicine. Previous research examining serum fibroblast growth factor 21 (FGF21) in humans has revealed equivocal relationships with clinical markers of metabolic dysfunction. However, it is unknown to what extent, if any, first‐degree family history of T2D (mother or father of the participant diagnosed with T2D) level affects serum FGF21 levels. The aim of this study was to determine whether in healthy individuals with FH+ (n = 18) and without FH‐ (n = 17) a family history of T2D affects serum FGF21.

Description and Predictive Value of a Novel Method for Determining the Respiratory Compensation Point Using Standard Scores

Abstract Bellar, DM, Judge, LW, and Davis, GR. Description and predictive value of a novel method for determining the respiratory compensation point using standard scores. J Strength Cond Res 29(5): 1433–1438, 2015—The ability to use data from tests of maximum aerobic capacity to estimate the ventilatory threshold and point of respiratory compensation (RCP) is useful for coaches and practitioners in the development of training schemes. Current methods for determining the RCP generally involve identifying deflections in respiratory variables when examined alongside minute ventilation. This investigation describes a novel mathematical method for determining RCP using standard scores (Z-scores) for minute ventilation (VE) and oxygen consumption ( ). This method allows for the point where ventilation becomes disproportionate to oxygen consumption to be quantified as an intersection between 2 lines of best fit. This novel Z-score method was compared with a well-described determination of RCP and was found to be highly correlated (r = 0.926, p ⩽ 0.001). The Z-score method was also found to be related to 10-km road race performance using regression analysis (R 2 = 0.824, p ⩽ 0.001) in a group of 18 athletes and recreational runners. Based on the evidence from this study, the Z-score method of RCP determination is highly correlated to previous methods and endurance performance. This method potentially offers further benefits as it is not reliant on visual determination of changes in slope in variables of interest but rather on the mathematical solution to the intersection of 2 regression lines.

Cognitive Function and Salivary DHEA Levels in Physically Active Elderly African American Women

Serum and plasma dehydroepiandrosterone sulfate (DHEAS) concentration has been associated with several health parameters associated with aging including cognitive function, bone mineral density, and muscular strength. However, the effectiveness of salivary DHEA for the prediction of cognitive function, bone mineral density, and muscular strength in older adults is currently unknown. Thirty elderly African American females provided early morning salivary samples and DHEA levels were determined using a commercially available immunoassay. Participants completed testing for psychomotor and executive function via Trail Making Tests (TMT) A and B, respectively. Bone ultrasound attenuation (BUA) was used to bone density and an isometric mid-thigh pull (IMTP) was used to determine isometric strength. Age significantly correlated with time on TMT A (r=0.328) and B (r=0.615) but was not related to DHEA, BUA, or IMTP outcomes. Elevated DHEA was associated with longer time to completion for TMT A (χ 2 = 5.14) but not to TMT B. DHEA levels were not associated with BUA or IMTP outcomes. While elevated levels of DHEA were correlated with impaired psychomotor function, salivary DHEA is not associated with executive function, bone mineral density, or isometric strength in elderly African American women.

The Effects of a 36-Hour Mixed Task Ultraendurance Race on Mucosal Immunity Markers and Pulmonary Function

OBJECTIVE The present study was conducted to assess the changes in mucosal immunity and pulmonary function among participants in a 36-hour mixed task ultraendurance race. METHODS Thirteen of the 20 race participants volunteered for the investigation (age 34±5 y). The event consisted of a mixture of aerobic, strong man, and military-style exercise. Participants had a pulmonary function test and gave a finger stick capillary blood sample and unstimulated saliva samples both before the event and upon dropout or completion. The blood sample was analyzed for hematocrit, and the saliva sample was analyzed for salivary flow rate, salivary alpha amylase, salivary immunoglobulin A (IgA), and IgA type 1. RESULTS Significant differences were noted among the finishers and those who dropped out in salivary flow rate (P = .026), salivary IgA (P = .017), and peak expiratory flow (P = .05) measurements. Salivary flow rate and IgA for the race finishers were reduced from pre- to postrace, whereas the nonfinishers showed no change or small increases. No significant differences emerged for other variables. CONCLUSIONS Based on the results of the present investigation, finishing a 36-hour mixed task ultra-endurance event results in a decline in both pulmonary function and mucosal immunity compared with competitors who do not finish.

Effects of an Elastic Hamstring Assistance Device During Downhill Running

Abstract The purpose of this study was to determine the appropriateness of using an elastic hamstring assistance device to reduce perceived levels of soreness, increase isometric strength, increase passive range of motion, and decrease biomarkers of muscle damage after eccentric exercise, specifically, downhill running This study was conducted in a university exercise physiology laboratory placing sixteen apparently healthy males (X = 21.6 ± 2.5 years) into two groups using a pre-test/post-test design. Pre-intervention measures taken included participants’ body height, body mass, body fat, capillary blood samples, VO2max, isometric hamstring strength at 45 and 90 degrees of flexion and passive hamstring range of motion. Post-intervention measures included blood biomarkers, passive range of motion, the perceived level of soreness and isometric strength. An analysis of normality of data was initially conducted followed by multivariate analysis of variance (MANOVA) of hamstring strength at 45 and 90 degrees of flexion, blood myoglobin and passive range of motion of the hamstrings. Statistically significant changes were noted in subject-perceived muscle soreness and isometric strength at 90 degrees at the 24-hour post-exercise trial measure between the two groups. Results would suggest the findings could be explained by the decrease in muscle soreness from utilizing the device during the exercise trial. Further research should be conducted to address sample size issues and to determine if the results are comparable on different surfaces.

The Efficacy of a Pre-Workout Vegan Supplement on High-Intensity Cycling Performance in Healthy College-Aged Males

ABSTRACT There is a limited supply of sport nutrition supplements currently available for vegan or vegetarian athletes. In addition, the efficacy of a vegan or vegetarian pre-workout supplement that does not contain any processed ingredients or stimulants is currently unknown. The purpose of the current study was to examine the effects of an unprocessed vegan pre-workout supplement on high-intensity cycling performance. Participants completed three separate cycling trials following the consumption of a vegan pre-workout supplement, an isocaloric processed supplement, or a zero-calorie placebo supplement. Each supplement was consumed 30 minutes prior to each trial, and each cycling trial was separated by a minimum of 72 hours. Supplements were administered using a randomized, double-blind cross-over design. Each cycling trial was performed at a workload equal to 80% VO2peak until exhaustion. The average time in seconds (s) until exhaustion values for the vegan, isocaloric, and zero-calorie supplements were 482 ± 163, 480 ± 157, and 496 ± 238, respectively. Consumption of the vegan supplement did not significantly improve performance compared to an isocaloric and zero-calorie supplement (F = 0.12, p =.89). The results of this study indicate that individuals who choose a vegan pre-workout supplement (over an isocaloric or zero-calorie product) will not experience any acute decrements or ergogenic benefits in cycling performance. Although the present study does not support performance benefits of the tested vegan pre-workout supplement before cycling, additional research examining various exercise intensities and modalities is warranted.