Search

In habitats where stressors are frequent or persistent, it can become increasingly difficult for wildlife to appropriately match their endocrine responses to these more challenging environments. The dynamic regulation of glucocorticoid (GC) hormones plays a crucial role in determining how well individuals cope with environmental changes. Amphibians exposed to agricultural stressors can dampen aspects of their GC profile (baseline, agitation, recovery, stress responsiveness, and negative feedback) to cope in these stressful environments, but this dampening can lead to reductions in an individual's reactive scope and a loss of endocrine flexibility. Organic agriculture could potentially limit some of these effects, however, little is known about how amphibians respond physiologically to organic agricultural environments. We compared GC profiles of Hyla versicolor tadpoles from three treatments: natural ponds (<5% agriculture within 500m), ponds near organic farms, and ponds near conventional farms. We hypothesized that tadpoles would cope with agricultural habitats by dampening stress responsiveness and exhibiting more efficient negative feedback and that the magnitude of these changes in response would differ based on agricultural method. We found that tadpoles from conventional and organic ponds were less likely to downregulate GCs via negative feedback after stressor exposure than tadpoles from natural ponds. For agricultural tadpoles that did downregulate GCs after the stressor, we found lower stress responsiveness and faster downregulation to baseline corticosterone than tadpoles from natural ponds. These results point to an accumulation of wear-and-tear, leading to an overall reduction in reactive scope and limited GC flexibility in our agricultural tadpoles. Regardless of agricultural method used, agricultural tadpoles exhibited the same patterns of GC response, indicating that current efforts to incentivize farmers to switch to organic farming methods may not be sufficient to address negative agricultural impacts on amphibians., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Amanda R. Bryant reports financial support was provided by Texas State University. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Abstract: Waldman, HS, Bryant, AR, Parten, AL, Grozier, CD, and McAllister, MJ. Astaxanthin supplementation does not affect markers of muscle damage or inflammation after an exercise-induced muscle damage protocol in resistance-trained males. J Strength Cond Res 37(7): e413-e421, 2023-It is well documented that exercise-induced muscle damage (EIMD) decreases exercise performance by elevated inflammation and subjective discomfort. Due to its potent antioxidative properties, astaxanthin (AX) may serve as a potential dietary supplement strategy for mitigating delayed-onset muscle soreness (DOMS) and enhancing recovery and performance. This study aimed to investigate the effects of AX on markers of muscle damage, inflammation, DOMS, and anaerobic performance and substrate metabolism. Thirteen resistance-trained men (mean ± SD , age, 23.4 ± 2.1 years) completed a double-blind, counterbalanced, and crossover design with a 1-week washout period between 2, 4-week supplementation periods at 12 mg·d -1 of AX or placebo. After each supplementation period, subjects completed 2 trials, with trial 1 including a graded exercise test (GXT) and a 30-second Wingate and trial 2 including an EIMD protocol followed by the collection of fasting blood samples (pre-post) to measure creatine kinase, advanced oxidative protein products, C-reactive protein, interleukin-6, insulin, and cortisol. Astaxanthin supplementation had no statistical effects on markers of substrate metabolism during the GXT, Wingate variables, or markers of muscle damage, inflammation, or DOMS when compared with placebo (all p > 0.05). However, 4 weeks of AX supplementation did significantly lower oxygen consumption during the final stage of the GXT (12%, p = 0.02), as well as lowered systolic blood pressure (∼7%, p = 0.04), and significantly lowered baseline insulin values (∼24%, p = 0.05) when compared with placebo. Collectively, these data suggest that 4 weeks of AX supplementation at 12 mg·d -1 did not affect markers of muscle damage, inflammation, or DOMS after an EIMD protocol in a resistance-trained male cohort., (Copyright © 2022 National Strength and Conditioning Association.)

Abstract: Waldman, HS, Bryant, AR, Knight, SN, Killen, LG, Davis, BA, Robinson, MA, and O'Neal, EK. Assessment of metabolic flexibility by substrate oxidation responses and blood lactate in women expressing varying levels of aerobic fitness and body fat. J Strength Cond Res 37(3): 581-588, 2023-Collection of substrate oxidation responses during exercise is proposed as a noninvasive means for assessing metabolic flexibility in male subjects. However, because of hormonal and metabolic differences between sexes, this method may not be applicable to female subjects. This study assessed metabolic flexibility through indirect calorimetry across female subjects with different maximal oxidative capacities. Thirty-eight (18-45 years) eumenorrheic female subjects were stratified ( p < 0.05) based on V̇ o2 peak (mL·kg -1 ·min -1 ) into (1) endurance-trained (ET, n = 12, 42.6 ± 5.3), (2) recreationally active (RA, n = 13, 32.3 ± 1.6), or (3) overweight female subjects (OW, n = 13, 21.0 ± 4.0). Subjects completed the same 5-stage graded exercise test with intensities of 30, 45, 60, 75, and 90 W. Lactate [La - ], carbohydrate (CHOox), and fat (FATox) oxidation rates were assessed during the last min of each 5-minute stage. Subjects then cycled to exhaustion to determine V̇ o2 peak. Endurance-trained and RA female subjects expressed significantly ( p ≤ 0.05) higher absolute rates and rates scaled to fat-free mass of CHOox and FATox compared with OW female subjects during multiple stages. [La - ] failed to consistently differentiate the 3 groups with higher [La - ] for OW only found during stage 4; however, RER differed by 0.09 units or more at each stage for OW vs. ET. It seems that RER was more sensitive to cohort characteristics than [La - ] contrasting recent findings in male cohorts. In conclusion, indirect calorimetry is a practical and noninvasive method for assessing metabolic flexibility in eumenorrheic female subjects of varying aerobic fitness levels., (Copyright © 2022 National Strength and Conditioning Association.)

Betaine (BET) has shown to be effective in improving body composition and performance, although research in women is lacking. This study investigated the effects of BET supplementation on markers of metabolic flexibility, body composition, and anaerobic performance in college females. Twenty-three active subjects with 21.8 ± 3.0 years of age, 66.6 ± 8.8 kg body mass, 1.6 ± 0.1 m height, and 23.2 ± 5.3% body fat performed a graded exercise test on a cycle ergometer consisting of 4 incremental, 3 min stages for collection of fat and carbohydrate oxidation rates. Three 10 s sprint tests were then completed against a resistance of 7.5% of body mass, separated by 2.5 min of recovery. The study comprised 3 phases: (a) pre-supplementation, (b) randomization to supplement for 2-weeks with either 2.4 g/day BET or placebo (parallel design), and (c) post-supplementation. Repeated-measures analysis of variance were conducted to determine interactions or main effects. There were no group differences for substrate oxidation rates ( p  > 0.05). Although body composition improved pre-post for both groups ( p  < 0.05), only the BET group experienced a significant increase in fat free mass ( p  < 0.01; ∼3%). Further, only the BET group experienced improvements to performance such as a higher mean power output during the final sprint ( p  = 0.02; ∼3%) and a lower RPE during the final stage of the graded exercise test ( p  = 0.02). Results from this study suggest BET supplementation may improve body composition and some markers of performance during exercise in collegiate women.

Invasive fish predators are an important factor causing amphibian declines and may have direct and indirect effects on amphibian survival. For example, early non-lethal exposure to these stressors may reduce survival in later life stages, especially in biphasic species. In amphibians, the glucocorticoid hormone corticosterone is released by the hypothalamo-pituitary-interrenal axis (HPI), as an adaptive physiological response to environmental stressors. The corticosterone response (baseline and response to acute stressors) is highly flexible and context dependent, and this variation can allow individuals to alter their phenotype and behavior with environmental changes, ultimately increasing survival. We sampled larvae of the spring salamander ( Gyrinophilus porphyriticus ) from two streams that each contained predatory brook trout ( Slavelinus fontinalis ) in the lower reaches and no predatory brook trout in the upper reaches. We measured baseline and stress-induced corticosterone release rates of larvae from the lower and upper reaches using a non-invasive water-borne hormone assay. We hypothesized that corticosterone release rates would differ between larvae from fish-present reaches and larvae from fish-free reaches. We found that baseline and stressor-induced corticosterone release rates were downregulated in larvae from reaches with fish predators. These results indicate that individuals from reaches with predatory trout are responding to fish predators by downregulating corticosterone while maintaining an active HPI axis. This may allow larvae more time to grow before metamorphosing, while also allowing them to physiologically respond to novel stressors. However, prolonged downregulation of corticosterone release rates can impact growth in post-metamorphic individuals.

Abstract: Waldman, HS, Bryant, AR, Shepherd, BD, Egan, B, and McAllister, MJ. No effect of a ketone monoester on markers of stress and performance in a live-burn search and rescue in firefighters. J Strength Cond Res 36(3): 763-771, 2022-Firefighters experience a range of stressors that impair performance and elevate the risk for developing cardiometabolic diseases. β-Hydroxybutyrate (βHB) has been shown to mitigate markers of oxidative stress and inflammation and serve as an alternative fuel with implications to physical performance. On 2 occasions in a double-blind, counterbalanced, and crossover design, 14 professional firefighters performed a live-burn, search and rescue (S&R) 30 minutes after ingestion of a ketone monoester (KME; 0.5 g·kg-1) or a placebo (PLA). Dependent variables collected before and after the S&R included salivary markers of stress and inflammation (cortisol, α-amylase, interleukin-1 beta, uric acid), perceptual markers (profile of mood state [POMS]), gastrointestinal distress (GI), rating of perceived exertion [RPE]), time to completion, and capillary blood measurement of βHB and glucose. KME resulted in capillary βHB concentrations of approximately 2.1-3.2 mM throughout the protocol. Capillary glucose concentrations were lower for the KME compared with PLA (∼7%) (interaction effect, p < 0.001). Salivary markers of stress, GI, and time to complete the S&R (∼10 minutes) did not differ between trials, although KME ingestion resulted in significantly higher RPE after the live-burn S&R (KME,6 ± 1; PLA, 4 ± 1). However, POMS data showed the KME also lowered subjective states of nervousness (KME, 0.0 ± 0.0; PLA, 0.6 ± 0.8) and anxiety (KME, 0.0 ± 0.0; PLA, 0.6 ± 0.7) before the S&R (all p < 0.05; large effect sizes). Compared with PLA, ingestion of a KME by firefighters did not mitigate the rise in various markers of salivary stress or impact physical performance during a live-burn S&R. However, differences in RPE and POMS variables were observed, suggesting a possible cognitive role for βHB., (Copyright © 2022 National Strength and Conditioning Association.)