Dina Christina Janse van Rensburg

Autonomic impairment in rheumatoid arthritis

To determine if there is a difference between autonomic cardiac control as measured by heart rate variability (HRV) in women with rheumatoid arthritis (RA) compared to a healthy control group.

Importance of Tachogram Length and Period of Recording during Noninvasive Investigation of the Autonomic Nervous System

Background: Various disciplines use quantification of heart rate variability (HRV) as an indicator of autonomic function without recognizing the importance of using standardized methodologies. The aim of this study was to assess the influence of tachogram length and period of recording on HRV indicator values.

Relationship between exercise capacity and heart rate variability : supine and in response to an orthostatic stressor

The study investigated whether supine-measured HRV indicators, and/or HRV indicators measured during orthostatic stress are related to conventional measures of exercise and performance ability such as VO(2max). Only two significant correlations (p<0.05) out of 30 tests were found between supine-determined HRV indicators and conventional measures. In contrast, fifteen of the 30 relationships calculated during orthostatic stress were significant. Relationships were at best low to moderate (0.2<|corr|<0.4). As expected, the relationships obtained during orthostatic stress were reversed from that obtained in the supine position. In summary, although HRV indicators are related to cardiovascular fitness, correlations between VO(2max) and these parameters are found only under very specific conditions. HRV parameters explain very little of the variance in VO(2max). In addition, estimating the exercise capacity from HRV indicators requires experience and extreme caution.

A comparison between heart rate and heart rate variability as indicators of cardiac health and fitness

Quantification of cardiac autonomic activity and control via heart rate (HR) and heart rate variability (HRV) is known to provide prognostic information in clinical populations. Issues with regard to standardization and interpretation of HRV data make the use of the more easily accessible HR on its own as an indicator of autonomic cardiac control very appealing. The aim of this study was to investigate the strength of associations between an important cardio vascular health metric such as VO2max and the following: HR, HRV indicators, and HR normalized HRV indicators. A cross sectional descriptive study was done including 145 healthy volunteers aged between 18 and 22 years. HRV was quantified by time domain, frequency domain and Poincaré plot analysis. Indirect VO2max was determined using the Multistage Coopers test. The Pearson correlation coefficient was calculated to quantify the strength of the associations. Both simple linear and multiple stepwise regressions were performed to be able to discriminate between the role of the individual indicators as well as their combined association with VO2max. Only HR, RR interval, and pNN50 showed significant (p < 0.01, p < 0.01, and p = 0.03) correlations with VO2max. Stepwise multiple regression indicated that, when combining all HRV indicators the most important predictor of cardio vascular fitness as represented by VO2max, is HR. HR explains 17% of the variation, while the inclusion of HF (high frequency HRV indicator) added only an additional 3.1% to the coefficient of determination. Results also showed when testing the normalized indicators, HR explained of the largest percentage of the changes in VO2max (16.5%). Thus, HR on its own is the most important predictor of changes in an important cardiac health metric such as VO2max. These results may indicate that during investigation of exercise ability (VO2max) phenomena, quantification of HRV may not add significant value.

Iliac artery endofibrosis in a middle-aged female long-distance runner.

Exercise-induced iliac artery endofibrosis is a recently described abnormality of the external iliac artery that typically affects younger, healthy endurance athletes. Characteristic of the initially termed cyclists iliac syndrome is lower limb pain during exercise with rapid recovery after exercise. This clinically complicated case describes an older female long-distance runner in whom an incorrect diagnosis of fibromuscular dysplasia was originally made when she presented with claudication and thrombosis of the right external iliac artery. A thrombectomy and bilateral balloon angioplasty were performed; however, her symptoms persisted. Four months later, she unexpectedly complained of dual calf claudication, a diagnosis of exercise-induced iliac artery endofibrosis was made, and a bilateral prosthetic graft bypass procedure was performed, which resulted in a good outcome.

The contribution of preintervention blood pressure, VO2max, BMI, autonomic function and gender to exercise-induced changes in heart rate variability

Introduction The quantification of heart rate variability (HRV) is a tool to assess the interaction between exercise and autonomic control, as well as the pathophysiology of diseases affecting autonomic function. Little is known about the influence of genetically influenced physiology on exercise-induced changes in autonomic cardiac regulation. It was theorised that preintervention values for blood pressure, VO2max, body mass index (BMI), autonomic function and gender contribute significantly to the exercise-induced changes in HRV. Methods A 12-week, medium-to-high intensity exercise intervention was completed by 183 volunteers (18–22 years). Data were sampled at baseline and after 12 weeks. Standard time domain, frequency domain and Poincaré HRV quantification techniques were implemented. Regression analysis was performed to determine the influences of the predictors (baseline values for low frequency (LF), high frequency (HF), BMI, VO2max, gender, blood pressure) on the exercise-induced response of the dependent variables (changes in HRV-indicator values). Results Parameters found to be significant (p<0.05) predictors of exercise-induced changes were LF, HF and systolic blood pressure in, respectively, 10, 5 and 2 of the 12 regressions performed. The results indicated that the independent variables contribute between 12.83% and 29.82%, depending on the specific HRV indicator, to the exercise-induced changes in the autonomic nervous system. Conclusions Preintervention autonomic status, as represented specifically by LF, is the most important determinant of cardiac autonomic response to an exercise intervention in a healthy study population. Baseline autonomic function could thus be a significant confounder in the outcome of exercise study results.

The Difference Between Exercise-Induced Autonomic and Fitness Changes Measured After 12 and 20 Weeks of Medium-to-High Intensity Military Training.

Abstract Grant, CC, Mongwe, L, Janse van Rensburg, DC, Fletcher, L, Wood, PS, Terblanche, E, and du Toit, PJ. The difference between exercise-induced autonomic and fitness changes measured after 12 and 20 weeks of medium-to-high intensity military training. J Strength Cond Res 30(9): 2453–2459, 2016—The aim of this study was to compare the physical fitness, based on VO2max and exercise-induced cardiac autonomic changes, measured by heart rate variability (HRV) of 12 weeks with 20 weeks of training in the South African National Defence Force. Recruits (n = 154) participated in a medium-to-high intensity exercise intervention (daily energy expenditure: 8,485 kJ·d−1). The significant effect on VO2max between weeks 1 and 12 (48.57, SD = 9.25 vs. 53.36, SD = 7.21] did not continue during weeks 12–20 (53.36, SD = 7.21 vs. 53.87, SD = 7.87). No changes in the supine low frequency (LF)/high frequency (HF) (0.48, SD = 0.51 vs. 0.41, SD = 0.64) or the standing LF/HF (4.02, SD = 5.14 vs. 3.91, SD = 5.28), an indicator of autonomic balance and a possible indicator of overtraining syndrome, suggests that overtraining did not take place during weeks 12–20. This was confirmed with further decreases in supine and standing heart rate. However, the power of the vagal-induced variability continued to increase after 12 weeks. Increased vagal influence without concurrent change in autonomic balance may be interpreted as decreased sympathetic cardiac control. It is important to note that although no fitness changes were detected, positive cardiac autonomic conditioning did continue between weeks 12 and 20, as measured by increased vagal-induced HRV and decreased sympathetic influence on cardiac control. Results may be extrapolated to training in the normal population/athletes after a medium-to-high intensity exercise program, as this intervention was a closely monitored and standardized exercise program.

Incidence of injury and illness in South African professional male football players: a prospective cohort study.

BACKGROUND Medical illnesses and sports-related injuries both have an effect on athlete health and performance. Epidemiology of injury and illness has been extensively researched during international soccer tournaments and the European soccer season. Reports on injury location and severity differ across geographical regions, and there is limited information on injury epidemiology in African soccer leagues. No studies have investigated the illness burden in soccer in Africa. METHODS This was a prospective cohort study involving two soccer teams over the 10-month duration of the 2015/16 Premier Soccer League in South Africa. Team medical staff recorded daily soccer exposure, illness and injuries. Team-based match and training exposure was calculated and used to determine injury and illness incidence and burden over the soccer season. RESULTS Overall injury incidence was 2.2/1000 hours, with match injury incidence of 24.8/1000 hours and training injury incidence of 0.9/1000 hours. Time loss injuries accounted for 33 of the 44 injuries recorded. The most common time loss injury location was the knee (14 injuries, 42%). There were 7 minimal, 4 mild, 12 moderate and 10 severe injuries. Sprain/ligament injury (8 injuries) was the most common type, followed by meniscus/cartilage injury (7 injuries). Eleven illnesses were reported during the season, with an incidence of 0.7/1000 player days, and most were minimal in severity (8/11). The illness burden was 1.7/1000 player days. The respiratory (46%) and gastrointestinal (36%) systems were most commonly affected. CONCLUSIONS The incidence of injury was comparable with data reported internationally and mirrors the increased risk of injury during matches versus training. The nature of injury differed in that the knee was more frequently affected than the ankle or thigh, joint injuries were more common than muscle injuries, and there was a larger proportion of severe injuries. The illness burden was very low.

AN INCREASING INCIDENCE OF INJURIES DURING THE SUPER RUGBY TOURNAMENT: A PROSPECTIVE STUDY OVER 4 YEARS INVOLVING 69 194 PLAYER-HOURS

Background Rugby Union has one of the highest reported incidences of match injuries among all professional sports. The Super Rugby tournament is played annually between professional rugby union teams from three rugby-playing nations in the Southern hemisphere. Objective To determine if the incidence of injuries in the Super Rugby tournament decreased over a 4-year period. Design Prospective cohort study. Setting Super Rugby tournament. Patients (or Participants) 774 male players from 5 South African teams. Assessment of Risk Factors) Medical staff of South African teams participating in the 2012, 2013, 2014 and 2015 tournaments recorded all time loss injuries (all injuries and match injuries) and exposure hours (69 194 total playing hours; 6 132 match hours). Main Outcome Measurements Incidence of all injuries and match injuries (per 1000 hours play). Results The incidence of all injuries (per 1000 player hours; 95% CI) for each year was as follows: 2012 (9.2; 7.9–10.8); 2013 (11.6; 10.1–13.3); 2014 (11.4; 9.8–13.2), and 2015 (12.4; 10.9–14.1). The incidence of all injuries in 2015 was significantly higher compared to 2012. The overall incidence of match injuries (per 1000 player hours; 95% CI) for each year was as follows: 2012 (83.3; 69.4–99.2); 2013 (120.4; 103.6–139.2); 2014 (98.6; 83.3–116.0), and 2015(119.1; 102.9–137.2). The incidence of match injuries in 2013 and 2015 was significantly higher compared to 2012 and 2014. Conclusions There is an increased incidence of all injuries and match injuries in the Super Rugby tournaments between 2012–2015. After 2012, the incidence of match injuries is consistently higher than previously reported for senior male rugby players at elite/professional level (89–96 per 1000 hrs). There is an urgent need to introduce targeted injury prevention strategies in the Super Rugby tournament to reduce the risk of injuries.

Thoracic outlet syndrome in a patient with absent scalenus anterior muscle.

This case report describes the rare anomaly of an absent right anterior scalene muscle presenting with the symptoms and signs of the thoracic outlet syndrome. The thoracic outlet syndrome in our patient can be attributed to the absence of the right anterior scalene muscle, which resulted in the brachial plexus being in proximity to the subclavian vein and artery in a narrowed and abnormal interscalene space. In addition, the absence of the anterior scalene muscle resulted in the neurovascular structures being compressed onto the first rib in the costoclavicular space. The most likely cause of the presentation is, however, the possibility of the presence of aberrant muscle slips, which would cause compression of the structures in the anterior (venous) and posterior (neurological) sections of the thoracic outlet.