Andrew J. McKune

Heart rate variability in physically active individuals : reliability and gender characteristics : cardiovascular topics

Purpose To evaluate the reliability of short-term recordings (five minutes) of heart rate variability (HRV) and the association between HRV and gender. Methods HRV time- and frequency-domain parameters were calculated in 44 physically active students (21 males and 23 females) over four consecutive days. A Suunto t6 heart rate monitor was used to obtain inter-beat intervals (IBIs) that were then transferred to Kubios HRV analysis software. The relative reliability [intra-class correlation (ICC)] and absolute reliability, [typical error of measurement (TEM) and typical error of measurement as a percentage (TEM%)] of the HRV parameters were then calculated for day 2 versus day 3 and day 3 versus day 4, with day 1 being a familiarisation day. The following HRV parameters were calculated: (1) time domain: resting heart rate (RHR), R–R intervals (IBI), standard deviation of normal-to-normal intervals (SDNN), root mean square differences of the standard deviation (RMSSD), percentage of beats that changed more than 50 ms from the previous beat (pNN50); and (2) frequency domain: low-frequency normalised units (LFnu), high-frequency normalised units (HFnu), low-frequency to high-frequency ratio in normalised units (LF/HFnu). An analysis of variance (ANOVA) with Tukey post-hoc testing was performed to compare HRV parameters in males and females. Significance was set at p ≤ 0.05. Results The ICCs for both relationship 1 and 2 indicated primarily good to excellent (> 0.8) relative reliability. The lowest value was found in the LF/HFnu ratio (ICC = 0.36) for males. Absolute reliability was low with TEM% greater than 10% for all HRV parameters, except IBIs. Females demonstrated better relative (higher ICCs) and absolute reliability (lower TEM and TEM%) compared to males for the frequency domain. The relative and absolute reliability for the time domains were similar except for SDNN where the absolute reliability was higher in males. ANOVA illustrated significant gender differences for the LF/HFnu ratio (41% higher in males, p = 0.003), HFnu (12% higher in females, p = 0.02) and IBI (21% higher in females, p < 0.0001). Conclusions Short-term recordings of HRV over three consecutive days demonstrated a high relative reliability. However, a low absolute reliability indicated large day-to-day random variation in HRV, which would make the detection of intervention effects using HRV difficult in individual participants. Females were shown to have a higher parasympathetic modulation of HRV, which may indicate an underlying cardioprotective mechanism in females compared to males.

Influence of ultra-endurance exercise on immunoglobulin isotypes and subclasses.

Background: Strenuous exercise is associated with tissue damage. This activates the innate immune system and local inflammation. Interaction between innate and adaptive immunity is essential for maintaining health, suggesting that the adaptive immune system may also be altered by exercise. Objectives: To determine exercise induced changes in the adaptive immune system by measuring the immunoglobulin isotype and subclass response to an ultra-marathon. Methods: Venepuncture was performed on 11 experienced volunteers (six men, five women; mean (SD) age 43 (9.8) years) 24 hours before the projected finishing time and immediately after and 3, 24, and 72 hours after an ultra-marathon (90 km). Serum was stored at −80°C. IgM, IgD, IgA, IgG, IgG1, 2, 3, and 4, and total IgE were measured. Results: The following immunoglobulins were significantly (p⩽0.05) altered after the race: IgD, immediately (−51%) and 24 hours (−41%) after; IgM 24 hours after (−23%); total IgG immediately after (+12%). There were no reports of symptoms of upper respiratory tract infections after the ultra-marathon. Conclusions: In experienced ultra-endurance runners, alterations in immunoglobulin concentrations after a race suggest an enhanced immune response, including isotype switching, interactions with the innate immune system, and a secondary antibody response. These alterations may have a role in the maintenance of subject health after an ultra-marathon.

Change in performance in response to training load adjustment based on autonomic activity.

The primary aim of this study was to assess performance (Perf) changes in response to a new training strategy. Specifically, based on spectral analysis of heart rate variability (SA HRV) to determine autonomic nervous system (ANS) activity, training doses were adjusted to maintain vagal activity at a high and relatively stable level during training preparation. Trained athletes (5 male and 5 female) aged 23.2±4.2 years voluntarily participated in the study. ANS activity was assessed during an orthoclinostatic test, and was represented by calculating HRV variables and a total score index. Over 17 weeks, improvement (1.4-8.5%) and deterioration (0.1-8.8%) in Perf were detected in 7 and 3 athletes, respectively. A relationship (rs=0.684; P<0.05) between the change in Perf (ΔPerf) and supine PHF during season was found. Supine HRV indices (PHF, PT, and MSSD) for the last 3 weeks of the HRV-adjusting period correlated (rs=0.636; 0.648; 0.648, P<0.05) with ΔPerf. Based on the results, a high and relative stable vagal activity during preparation may indicate a readiness to train or appropriate recovery that positively affects Perf. In conclusion, daily quantification of ANS activity by SA HRV seems to be a promising tool for the enhancement of Perf.

Elevated salivary C-reactive protein predicted by low cardio-respiratory fitness and being overweight in African children

Introduction C-reactive protein (CRP) is a sensitive marker of systemic inflammation and is an independent risk factor for cardiovascular disease. The aim of the study was to examine the relationship between salivary CRP, cardio-respiratory fitness and body composition in a paediatric population. Methods This was a cross-sectional study of 170 black South African children (age 9.41 ± 1.55 years, 100 females, 70 males) in grades 3 to 7. Unstimulated whole saliva samples were obtained for the analysis of CRP. Height, mass, skin-fold thickness, resting blood pressure, and waist and hip circumference measurements were obtained. Cardio-respiratory fitness was assessed using a 20-m multi-stage shuttle run. Children were classified as overweight/obese according to the Center for Disease Control and Prevention (CDC) body mass index (BMI) percentile ranking, and meeting percentage body fat recommendations, if percentage body fat was ≤ 25% in boys and ≤ 32% in girls. The cut-off point for low cardio-respiratory fitness was a predicted aerobic capacity value ≤ the 50th percentile for the group. Contributions of low cardio-respiratory fitness, overweight/obesity, and not meeting percentage body fat recommendations, to elevated salivary CRP (≥ 75th percentile) concentration and secretion rate were examined using binary logistic regression analysis with a backward stepwise selection technique based on likelihood ratios. Results Poor cardio-respiratory fitness was independently associated with elevated salivary CRP concentration (OR 3.9, 95% CI: 1.7–8.9, p = 0.001). Poor cardio-respiratory fitness (OR 2.7, 95% CI: 1.2–6.1, p = 0.02) and overweight/obesity (BMI ≥ 85th percentile) (OR 2.5, 95% CI: 1.1–5.9, p = 0.03) were independent predictors of elevated salivary CRP secretion rate. Conclusion The results suggest a strong association between poor cardio-respiratory fitness and/or overweight/obesity and inflammatory status in children, based on elevated salivary CRP levels.

Serum concentrations of C reactive protein, α1 antitrypsin, and complement (C3, C4, C1 esterase inhibitor) before and during the Vuelta a Espańa

Objectives: To determine serum concentrations of proinflammatory (C reactive protein, complement C3 and C4) and anti-inflammatory (α1 antitrypsin, C1 esterase inhibitor (C1-INH)) acute phase proteins in elite cyclists before and during a three week cycle tour. Methods: Seventeen professional cyclists participating in the Vuelta a Espańa volunteered for the study. Their mean (SD) physical characteristics were: age 28 (1) years; height 1.7 (0.06) m; weight 65 (7) kg; body fat 7.6 (0.8)%; Vo2max 75.3 (2.3) ml/kg/min. Venepuncture was performed on each subject 24 hours before the tour began (T0), on day 11 (the first rest day; T1) and day 21 (the second to last stage of the tour; T2). Samples at T1 and T2 were taken about 17 hours after the previous stage. Analysis of variance was used to determine changes over time. Where significance was found, a Tukey post hoc test was performed. Results: C reactive protein concentrations were consistently within the normal range, although there was a 228%, non-significant increase at T1. C3 concentrations fell within the normal range at all times assessed. C4 concentrations before the race were within the normal range and were significantly increased 10 days (T1) into the race. C1-INH concentrations did not change significantly throughout the race. α1 Antitrypsin concentration before the race was at the lower end of the normal range and was only significantly raised at T2. Conclusions: Although not as pronounced as those reported in marathon/ultramarathon runners, elite cyclists participating in a three week cycle tour experienced increases in selected proinflammatory and anti-inflammatory acute phase proteins, indicating an acute phase/inflammatory response. It is tenable that the increase in α1 antitrypsin and C1-INH (anti-inflammatory mediators) at T2 served to attenuate the acute phase/inflammatory response. The lower than normal resting concentrations of the acute phase proteins supports the notion that chronic aerobic exercise induces an anti-inflammatory state.

ACUTE EXERCISE-INDUCED MUSCLE INJURY

While much research has recently been focussing on the chronic effects of overtraining, the acute damaging effects of individual eccentric exercise bouts on muscle remain of interest and underlie long-term training effects. Systemic markers of muscle damage are limited in terms of sensitivity and reliability. A clearer insight into the extent of the damage and mechanisms involved are being obtained from ultrastructural, functional and molecular examination of the muscle. There are currently indications that while the initial muscle damage may appear to have negative consequences in the short term, intense eccentric exercise appears to initiate a remodelling process and promote favourable adaptation of muscle following training, which has applications for promoting health, rehabilitation and sports performance.

A comparison of laser doppler fluxmetry and transcutaneous oxygen pressure measurement in the dysvascular patient requiring amputation

OBJECTIVE To determine the predictive power of laser Doppler fluxmetry (LDF), both heated and unheated, as a preoperative investigation of wound healing potential in dysvascular patients requiring amputation, by comparison with transcutaneous oxygen pressure measurement (TcpO2) and the limb to chest TcpO2 index. METHODS Thirty-five non-diabetic patients with peripheral vascular disease were investigated before amputation. Heated and unheated LDF and heated TcpO2 measurements were taken on the chest wall and at the routine above-knee, below-knee and mid-foot amputation levels. Wound healing potential was evaluated against a TcpO2 index value of 0.55 and on clinical outcome. RESULTS A heated LDF value of 4.9 arbitrary units (au) was shown by receiver-operator characteristic curve to have the best predictive power, with an overall accuracy for preoperative prediction of wound healing of 91.4%, and a predictive value for wound failure of 89%. Based on the heated LDF of 4.9 au, review of 26 amputations performed shows the overall accuracy for preoperative prediction of wound healing of 92.3%, a predictive value for wound healing of 100%, and a predictive value for wound failure of 62.5%. CONCLUSION A heated LDF value of 4.9 au appears to be a useful predictor of the potential of an amputation site to heal.

Immunoglobulin responses to a repeated bout of downhill running

Objective: To examine the effect of downhill running on immunoglobulin responses. Method: Eleven untrained men performed 2 × 60 minute bouts of downhill running (−13.5% gradient), at a speed eliciting 75% of their V̇o2peak on a level grade. Two runs were spaced 14 days apart. Serum samples were collected before, after, and every hour for 12 hours and every 24 hours for six days. Serum total creatine kinase and immunoglobulin isotypes and subclasses were measured, and results were analysed using a repeated measures analysis of variance (12 hour period, 2 × 14; 24 hour intervals, 2 × 6, p⩽0.05). Results: There was a significant interaction effect for creatine kinase (activity lower after run 2 than after run 1, 6–24 h) and exercise effect, with the serum concentrations of IgG1, IgG2, IgG4, and IgE lower, and IgM higher, after run 2. Conclusion: Lower concentrations of IgG1, IgG2, and IgE after run 2 may reflect a dampened autoimmune inflammatory response to autoantigens and enhanced autoantigen clearance mediated by the upregulation of IgM.

The Effects of Resveratrol Supplementation in Overweight and Obese Humans: A Systematic Review of Randomized Trials

BACKGROUND Obesity and metabolic syndrome are significant global health issues, with current public health messages predominately focused on altering dietary and physical activity behaviors. Resveratrol is a polyphenol (stilbenoid) commonly found in grapes, and human trials to date have shown conflicting and limited beneficial effects with respect to health. The aim of this study was to determine the effect of resveratrol supplementation on reducing body weight and modifying associated inflammatory markers. METHODS A systematic review was undertaken following the PRISMA guidelines and using five indexed databases (OVID MEDLINE, Cochrane Library, Web of Science, SCOPUS, and CINAHL). A search strategy was formulated to select randomized, double-blind, placebo-controlled human trials investigating the effects of resveratrol supplementation on obesity or overweight, including body weight, metabolic and inflammatory markers. RESULTS Five thousand five hundred sixty-nine studies published from 1990 to November 2015 were identified, with only nine papers meeting the inclusion criteria. The studies involved 208 participants (aged 49.2 ± 8.3 years) and utilized a substantial range of resveratrol doses (75-3000 mg/day). Study durations were a minimum of 2 weeks (14-90 days). Seven studies indicated no significant change in body mass index or body weight (P > 0.05), and three studies showed no improvements in fat mass, fat volume, or abdominal fat distribution (P > 0.05). Four studies included measurements of inflammatory markers, with three of these finding resveratrol supplementation to have a significant positive effect (P > 0.05). CONCLUSION Based on the included studies, there is currently insufficient evidence to support the recommendation of resveratrol supplements in management of obesity. However, there were significant but not entirely consistent anti-inflammatory effects after resveratrol supplementation in overweight and obese individuals.

Intestinal temperature, heart rate, and hydration status in multiday trail runners.

Objective:To assess heart rate (HR), intestinal body temperature (Tintest), and hydration status changes and relationships in 12 participants in a 3-day trail run. Design:Descriptive field study. Setting:Three Cranes Challenge trail run, in Karkloof, KwaZulu-Natal, South Africa. Participants:Twelve (5 men and 7 women) amateur runners. Interventions:Trail run of 95 km divided into 3 stages: elevation gains on the 3 days, 1020, 1226, and 680 m, respectively. Main Outcome Measures:Changes in HR, Tintest, serum osmolality, and body mass. Results:Environmental conditions were consistently mild (ambient temperature range, 11.5-22.8°C; maximum relative humidity range, 95%-97%), average running speed varied from 9.00 to 5.14 minutes/km, and distance covered in the 3 stages ranged from 32 (stages 1 and 3) to 40 km (stage 2). Mean HR ranged from 134 to 171 beats per minute in the 12 athletes during the trail events and averaged at 150 beats per minute, whereas Tintest ranged between 36.1 and 40.2°C. The correlation between maximum Tintest and percent age-predicted maximum HR (n = 12) was significant (R = 0.58; P < 0.05), whereas the correlation between maximum Tintest and serum osmolality or body mass did not reach significance (R = 0.16, 0.13; P > 0.05). Conclusions:This study provides evidence in support of the contention that maximum Tintest is more closely related to metabolic rate during trail running than percent dehydration. The findings do not support an increase in core body temperature with a change in serum osmolality or body mass.