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Evaluating the Clinical Utility of Daily Heart Rate Variability Assessment for Classifying Meaningful Change in Testosterone-to-Cortisol Ratio: A Preliminary Study.
DeBlauw, JA, Crawford, DA, Kurtz, BK, Drake, NB, Heinrich, KM
International journal of exercise science. 2021;14(3):260-273
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Exercise-induced hormonal responses are controlled by the hypothalamic-pituitary adrenal axis, a key regulator of homeostasis, which responds to stress by triggering a series of endocrine changes resulting in the release of testosterone (T) and cortisol (C). The aim of this study was to determine the relationship between daily resting heart rate variability (HRV) and pre-exercise T:C ratio and evaluate the clinical utility (i.e., diagnostic validity and reliability) of daily HRV assessment in classifying atypical T:C ratio changes throughout a nine-week high-intensity functional training (HIFT) intervention. This study is a secondary analysis of a subset of participants from a larger study. Eight recreationally active men and women ages 18-35 were recruited for participation. Following 14 days of baseline HRV assessments, participants were randomized to either the treatment or control condition. Results show a statistically significant negative relationship between HRVdaily and the T:C ratio throughout 9-weeks of HIFT. Additionally, there was no significant relationship found between C and HRVdaily and neither sex nor group were significant factors. Authors conclude that their findings emphasize the potential of HRV for the guidance of training, however, as hormonal responses to training are highly individual, the creation of individual autonomic nervous systems and hormonal profiles would increase the accuracy of training stress modulation.
Abstract
The study purpose was to determine the relationship of resting heart rate variability (HRV) and testosterone to cortisol (T:C) ratio, along with the diagnostic ability of HRV to assess changes in T:C ratio during a 9-week high-intensity functional training intervention. Eight recreationally-active men (n = 4, age 24.25 ± 1.75 yrs, height 181.25 ± 3.86 cm, weight 79.68 ± 11.66 kg) and women (n = 4, age 26 ± 3.6 yrs, height 164.25 ± 3.3, weight 73.4 ± 8.42) completed daily HRV measurements (HRVdaily) using photoplethysmography via a commercially-available smartphone application along with weekly saliva samples. Saliva samples were analyzed for concentrations of testosterone (T) and cortisol (C) via enzyme-linked immunosorbent assays. Upon study completion 72 data points were available, due to participant compliance and inadequate saliva sample, 67 matched pairs of HRV and T:C ratio were analyzed. A statistically significant negative relationship (n = 67, r = -.315, p < 0.05) was found between HRVdaily and saliva T:C ratio concentrations within aggregate data. Individual participant relationships showed considerable variability (r = -0.101 - 0.665, p = 0.103 to 0.829 The model which best explained the data resulted in AIC = 130.247 with factors HRVdaily (β = -0.218, 95%CI = -0.391, -0.044, t = -2.46, p < 0.05), Sex (β = 0.450, 95%CI = -0.214, 1.114, t = 1.113, p = 0.242), and Group (β = -0.394, 95%CI = -1.089, 0.302, t = -1.11, p = 0.311). Diagnostically, HRVdaily demonstrates excellent sensitivity (95%), but poor specificity (5%) for detecting meaningful changes in T:C ratio. Assessment of HRVdaily may be a clinically valid proxy measure for monitoring hormonal changes throughout a training intervention.
2.
Short-Term Exercise Training Inconsistently Influences Basal Testosterone in Older Men: A Systematic Review and Meta-Analysis.
Hayes, LD, Elliott, BT
Frontiers in physiology. 2018;9:1878
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The levels of testosterone decrease as men age and is associated with accelerated ageing. Approaches to increase testosterone levels may therefore be of benefit. There are complications with administering testosterone and so exercise has been proposed as a non-pharmacological intervention to increase serum testosterone in older males. The purpose of this review and meta-analysis was to look at suitable studies linking exercise and testosterone levels in older males and to see whether types of exercise (endurance, resistance and interval training) made a difference. There is a belief that resistance exercise increases basal testosterone over time. However, this was not observed in this meta-analysis. HIIT (high intensity interval training), and endurance training showed the most promise for increasing basal testosterone in older men. There is a need for more studies to improve the quality of available evidence and at present, exercise is probably the best non-pharmacological countermeasure to loss of muscle function with human aging.
Abstract
Background: The age-associated decrease in testosterone is one mechanism suggested to accelerate the aging process in males. Therefore, approaches to increase endogenous testosterone may be of benefit. The aim of this paper was to undertake a Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA)-accordant meta-analysis concerning the effect of exercise on total (TT), bioavailable (bio-T), free (free-T), and salivary (sal-T) testosterone in older males. Methods: Databases were searched up to and including 20th February 2018 for the terms "testosterone AND exercise AND aging AND males," "testosterone AND exercise AND old AND males," "testosterone AND training AND aging AND males," and "testosterone AND training AND old AND males". From 1259 originally identified titles, 22 studies (randomized controlled trials; RCTs; n = 9, and uncontrolled trials; UCTs; n = 13) were included which had a training component, participants ≥60 years of age, and salivary or serum testosterone as an outcome measure. Meta-analyses were conducted on change to testosterone following training using standardized difference in means (SDM) and random effects models. Results: The overall SDM for endurance training, resistance training, and interval training was 0.398 (95% CI = 0.034-0.761; P = 0.010), -0.003 (95% CI = -0.330-0.324; P = 0.986), and 0.283 (95% CI = 0.030-0.535; P = 0.028), respectively. Resistance training exhibited a qualitative effect of hormone fraction whereby free-T resulted in the greatest SDM (0.253; 95% CI = -0.043-0.549; P = 0.094), followed by TT (0.028; 95% CI = -0.204-0.260; P = 0.813), and resistance training negatively influenced bio-T (-0.373; 95% CI = -0.789-0.042; P = 0.078). Due to the small number of studies, subgroup analysis was not possible for endurance training and interval training studies. Conclusions: Data from the present investigation suggests that resistance training does not significantly influence basal testosterone in older men. Magnitude of effect was influenced by hormone fraction, even within the same investigation. Aerobic training and interval training did result in small, significant increases in basal testosterone. The magnitude of effect is small but the existing data are encouraging and may be an avenue for further research.