Anna Strasz

Determination and Prediction of One Repetition Maximum (1RM): Safety Considerations

Determination and Prediction of One Repetition Maximum (1RM): Safety Considerations Strength training is recommended for slowing age-dependent deterioration of muscular strength and for rehabilitating patients with muscle weakening illnesses. Reliable assessment of muscle strength is important for proper design of strength training regimes for prevention, rehabilitation, and sport. One repetition maximum (1RM) is an established measure of muscular strength and is defined as the value of resistance against which a given movement can be performed only once. Proper assessment of 1RM is time consuming, and may lead to muscle soreness as well as temporary deterioration of the function of the tested muscles. Attempts at indirect 1RM determination based on the maximum number of repetitions performed have predicted 1RM with a variable degree of accuracy. Cardiovascular safety has been neglected in 1RM determination, although arterial blood pressure increases considerably when exercising against maximal or near maximal resistance. From the perspective of cardiovascular safety, favorable 1RM measurement methods should avoid performance of repetitions until failure; movement against high resistance and muscle fatigue both increase blood pressure. Although such techniques are likely less accurate than the current methods, their prediction accuracy be sufficient for therapeutic strength training.

Impedance cardiography: Recent advancements

The aim of this paper is the presentation of recent advancements in impedance cardiography regarding methodical approach, applied equipment and clinical or research implementations. The review is limited to the papers which were published over last 17 months (dated 2011 and 2012) in well recognised scientific journals.

Effects of a brief Valsalva manoeuvre on hemodynamic response to strength exercises

Strength training is a recommended measure against loss of strength and muscle mass because of age‐ or illness‐induced inactivity. Strength exercises may impose heavy cardiovascular load by increasing heart rate and blood pressure. To increase strength efficiently, a heavy load has to be applied; this, however, leads to a spontaneous Valsalva manoeuvre, which additionally raises blood pressure. Avoidance of this manoeuvre is recommended. If the additional rise in arterial blood pressure caused by Valsalva manoeuvre is smaller than intrathoracic or intracranial pressures during this manoeuvre, Valsalva manoeuvre may actually protect arteries located in the thorax and in the brain by diminishing transmural pressure acting across these vessels. Effect of controlled breathing or brief Valsalva manoeuvre on arterial pressure at rest and during knee extension against 15‐repetition maximum resistance was evaluated. In 12 healthy young men blood pressure was measured continuously and non‐invasively, knee angle, speed of respiratory air or mouth pressure (MP) were continuously registered. Each combination of respiratory and exercise manoeuvres was repeated six times, for every of last three repetitions peak and trough systolic and diastolic pressure were determined. Strength exercises elevated peak pressures more than trough pressures, systolic more than diastolic. Valsalva manoeuvre increased only peak systolic and peak diastolic pressure. This increase was in average lesser than MP, thus rendering an argument in favour of protective role of brief Valsalva manoeuvre because of decline in transmural pressure acting on thoracic and possibly cerebral arteries. However, there was strong individual variability, and in few instances, arterial pressure increased because of brief Valsalva manoeuvre more than MP; thus in some subjects, the manoeuvre might enhance transmural pressure acting on thorax arteries.

Early hemodynamic response to the tilt test in patients with syncope.

Introduction Our aim was to evaluate the differences in the early hemodynamic response to the tilt test (HUTT) in patients with and without syncope using impedance cardiography (ICG). Material and methods One hundred twenty-six patients (72 female/48 male; 37 ±17 years) were divided into a group with syncope (HUTT(+), n = 45 patients) and a group without syncope (HUTT(–), n = 81 patients). ECG and ICG signals were continuously recorded during the whole examination, allowing the calculation of heart rate (HR), stroke volume (SV), and cardiac output (CO) for every beat. The hemodynamic parameters (averaged over 1 min) were analyzed at the following points of the HUTT: the last minute of resting, the period immediately after the tilt (0 min), 1 min and 5 min after the maneuver. The absolute changes of HR, SV and CO were calculated for 0, 1, and 5 min after the maneuver in relation to the values at rest (ΔHR, ΔSV, ΔCO). Also, the percentage changes were calculated (HRi, SVi, COi). Results There were no differences between the groups in absolute and percentage changes of hemodynamic parameters immediately after and 1 min after tilting. Significant differences between the HUTT(+) and HUTT(–) groups were observed in the 5th min of tilting: for ΔSV (–27.2 ±21.2 ml vs. –9.7 ±27.2 ml; p = 0.03), ΔCO (–1.78 ±1.62 l/min vs. –0.34 ±2.48 l/min; p = 0.032), COi (–30 ±28% vs. –0.2 ±58%; p = 0.034). Conclusions In the 5th min the decrease of hemodynamic parameters (ΔSV, ΔCO, COi) was significantly more pronounced in HUTT(+) patients in comparison to the HUTT(–) group.

Relationships Between Systolic Time Intervals and Heart Rate During Initial Response to Orthostatic Manoeuvre in Men of Different Age

Relationships Between Systolic Time Intervals and Heart Rate During Initial Response to Orthostatic Manoeuvre in Men of Different Age An analysis of transient changes in physiological parameters in response to the standardized tests could be used to evaluate the efficiency of the regulatory processes. Relationships between systolic time intervals and heart rate following the action of standing up from the supine position were investigated in 41 healthy men, aged 20 to 59 years, classified into three groups: (22 to 26 yrs, n=14), (33 to 49, yrs, n=13) and (51 to 59 yrs, n=14). The protocol consisted of the following sequence: laying down (20 minutes) - standing up (8 minutes). Ejection time, pre-ejection period, electromechanical systole, heart rate and the length of R-R intervals were continuously calculated using automatized impedance cardiography and electrocardiogram. The ratio of ejection time to pre-ejection period in young men was significantly higher in comparison with the other groups. The ratio of ejection time to the length of R-R interval increased with age in supine position and after standing up when R-R interval was maximal. It was suggested that changes of ejection time to pre-ejection period during the orthostatic manoeuvre are rather the result of balance between heart rate and hemodynamic factors, than solely related to heart rate.

Empirical Mode Decomposition in Analysis of Hemodynamic Response to Static Handgrip

The empirical mode decomposition (EMD) of biological signals is used to detect reaction to physiological stimuli and to identify global trends in slowly changing variables. We applied EMD to analyze hemodynamic reaction to handgrip in 9 healthy males (aged 21.3 ± 0.3 years) and 10 male patients following coronary artery bypass grafting (aged 55 ± 6 years). Subjects squeezed a dynamometer with 30% of individually determined maximal force for 3 min. The aim of the study was to check whether the application of EMD to the signals could bring any objective quantitative or qualitative measures allowing one to distinguish physiological states of healthy subjects and patients. Hemodynamic data were collected using a battery-powered, ambulatory impedance cardiography device (ReoMonitor) incorporating a single ECG channel. Heart rate (HR), R-R interval (RR), stroke volume (SV), cardiac output (CO), left ventricular ejection time (ET), pre-ejection period (PEP), maximum amplitude of the dz/dt signal (Amp), and basic chest impedance (Z0) were calculated automatically using the software earlier developed for ReoMonitor. The dedicated computer program allows to calculate and display the dynamics of basic and derivative parameters, describing the impact of systolic time intervals on RR intervals, or the relationship between them (e.g. PEP/ET). The EMD procedure was applied to identify the components of each basic hemodynamic parameter and all their derivatives. We observed the most pronounced effect of handgrip in second and third intrinsic mode functions (IMF), which particularly manifested in parameters describing the ratio of systolic time intervals to the length of RR.

In aged men, central vessel transmural pressure is reduced by brief Valsalva manoeuvre during strength exercise.

A brief Valsalva manoeuvre, lasting 2–3 s, performed by young healthy men during strength exercise reduces transmural pressure acting on intrathoracic arteries. In this study, we sought to verify this finding in older men. Twenty normotensive, prehypertensive and moderately hypertensive otherwise healthy men 46–69 years old performed knee extensions combined with inspiration or with brief Valsalva manoeuvre performed at 10, 20 and 40 mmHg mouth pressure. Same respiratory manoeuvres were also performed at rest. Non‐invasively measured blood pressure, knee angle, respiratory airflow and mouth pressure were continuously registered. In comparison to inspiration, estimated transmural pressure acting on thoracic arteries changed slightly and insignificantly during brief Valsalva manoeuvre at 10 and 20 mmHg mouth pressure. At 40 mmHg mouth pressure, transmural pressure declined at rest (−8·8 ± 11·4 mmHg) and during knee extension (−12·1 ± 11·9 mmHg). This decline ensued, as peak systolic pressure increase caused by this manoeuvre, was distinctly <40 mmHg. Only a main effect of mouth pressure was revealed (P<0·001) and neither exercise nor interaction between these factors, what suggests that transmural pressure decline, depended mainly on intrathoracic pressure developed during brief Valsalva manoeuvre. Resting blood pressure did not influence the effect of brief Valsalva manoeuvre on transmural pressure.

Systolic Time Intervals Detection and Analysis of Polyphysiographic Signals

The newly developed computer program allows the continuous measurement of the following systolic time intervals (STI): PEP – preejection period, Q − S2 - time between trough of Q wave and aortic valve closure, Q − D - time between trough of Q wave and dicrotic notch, S2 − D - time between aortic valve closure and dicrotic notch, as well as QQ interval. The program was tested on the recordings obtained in 30 young, healthy subjects remaining in supine position who performed twice two-minute isometric handgrip (HG). First HG was followed by four-minute rest, second HG by two-minute occlusion of the working arm. Since there were distinct oscillation in the time course of Q − S2 intervals and the time course of Q − D intervals was relatively smooth, we suggested that S2 and D might reflect different events which is in contrary to common notation.