Papers by Christina Spengler
Frontiers in digital health, Jun 17, 2024
Advances in Experimental Medicine and Biology, 2001
When modeling the respiratory control system, it is useful to know the inherent noise in the vari... more When modeling the respiratory control system, it is useful to know the inherent noise in the variables of interest, such as the arterial PCO2 and the sensitivity of the hypercapnic ventilatory response (HCVR). These variables can be greatly affected by behavioral and environmental conditions including fluctuations in arousal level, emotion, cognitive activity, subject-experimenter interaction, light, noise and temperature. For instance, even when in an ostensible steady-state, merely opening one’s eyes results in systematic increases in breathing frequency, ventilation and HCVR slope (reviewed by Shea1). In addition, challenges to the respiratory control system (e.g., added loads, hypoxia or hypercapnia) can result in adaptation such that subsequent measurements are affected by prior measurements (e.g., Powell et al2). Furthermore there can be non-physiological variability that is intrinsic to the measurement technique itself (e.g., instability of sensors). Overall, influences from behaviors, arousal, the environment, adaptation and the measurement technique contribute to the ‘noise’ in the measured data.
Applied Ergonomics, May 1, 2014
The purpose of this study was to compare physical workload, electromyography (EMG) of the trapezi... more The purpose of this study was to compare physical workload, electromyography (EMG) of the trapezius muscle, neck pain and mental well-being at work between night and day shifts in twenty Swiss nurses. Work pulse (average increase of heart rate over resting heart rate) was lower during night (27 bpm) compared to day shifts (34 bpm; p < 0.01). Relative arm acceleration also indicated less physical activity during night (82% of average) compared to day shifts (110%; p < 0.01). Rest periods were significantly longer during night shifts. Trapezius muscle rest time was longer during night (13% of shift duration) than day shifts (7%; p < 0.01) and the 50th percentile of EMG activity was smaller (p ¼ 0.02), indicating more opportunities for muscle relaxation during night shifts. Neck pain and mental well-being at work were similar between shifts. Subjective perception of burden was similar between shifts despite less physical burden at night, suggesting there are other contributing factors.
Physiological Measurement, Jul 3, 2018
OBJECTIVE Locally increasing evaporative resistance is one mechanism by which contact skin temper... more OBJECTIVE Locally increasing evaporative resistance is one mechanism by which contact skin temperature (T sk) sensors and their attachments may disturb the temperature of the skin site being measured. We aimed to determine the extent to which an obstruction of evaporation affects local T sk during exercise-induced sweating and how this compares to the T sk measured using a conventional contact T sk sensor. APPROACH Twelve adult males each completed one experimental session (~24 °C, ~46% relative humidity) involving seated rest and exercise (cycle ergometer). Air velocity was ~0.5 m · s-1 during rest and ~1 m · s-1 during exercise. T sk of the right posterolateral forearm was measured using fine-wire thermocouples (0.125 mm diameter; chosen for minimal sensor-related disturbance) under two concurrent experimental conditions: uncovered or directly covered by a moisture-impermeable matte-black aluminium foil (thickness 0.08 mm, area 15 mm × 22 mm). The adjacent T sk was also measured using an iButton attached with a nonwoven medical tape. Changes in next-to-skin absolute vapour pressure were used to estimate the onset of sweating. MAIN RESULTS During exercise, covered thermocouple temperatures were consistently warmer than those uncovered. These differences were small before the onset of sweating (0.1 °C, p = 0.16), but increased thereafter (0.6 and 1.0 °C by minutes 15 and 30 of exercise, respectively; p ⩽ 0.03). For change scores from baseline rest, the iButton-measured T sk was as much as 0.7 °C warmer than uncovered and -0.4 °C cooler than covered thermocouples during sweating, but differences were not statistically supported and with wide 95% limits of agreement (up to ±3.1 °C). SIGNIFICANCE When delineated, a small obstruction of evaporation itself caused an overestimation of T sk during exercise although, while demonstrable, these effects were less clear in the context of using a conventional contact T sk sensor and attachment.
Annals of occupational and environmental medicine, Nov 19, 2018
Objective: Normobaric (NH) and hypobaric hypoxia (HH) are associated with acute mountain sickness... more Objective: Normobaric (NH) and hypobaric hypoxia (HH) are associated with acute mountain sickness (AMS) and cognitive dysfunction. Only few variables, like heart-rate-variability, are correlated with AMS. However, prediction of AMS remains difficult. We therefore designed an expedition-study with healthy volunteers in NH/HH to investigate additional non-invasive hemodynamic variables associated with AMS. Methods: Eleven healthy subjects were examined in NH (FiO 2 13.1%; equivalent of 3.883 m a.s.l; duration 4 h) and HH (3.883 m a.s.l.; duration 24 h) before and after an exercise of 120 min. Changes in parameters of electrical cardiometry (cardiac index (CI), left-ventricular ejection time (LVET), stroke volume (SV), index of contractility (ICON)), near-infrared spectroscopy (cerebral oxygenation, rScO 2), Lake-Louise-Score (LLS) and cognitive function tests were assessed. One-Way-ANOVA, Wilcoxon matched-pairs test, Spearman's-correlation-analysis and Student's t-test were performed. Results: HH increased heart rate (HR), mean arterial pressure (MAP) and CI and decreased LVET, SV and ICON, whereas NH increased HR and decreased LVET. In both NH and HH cerebral oxygenation decreased and LLS increased significantly. After 24 h in HH, 6 of 11 subjects (54.6%) developed AMS. LLS remained increased until 24 h in HH, whereas cognitive function remained unaltered. In HH, HR and LLS were inversely correlated (r = − 0.692; p < 0.05). More importantly, the rScO2-decrease after exercise in NH significantly correlated with LLS after 24 h in HH (r = − 0.971; p < 0.01) and rScO2 correlated significantly with HR (r = 0.802; p < 0.01), CI (r = 0.682; p < 0.05) and SV (r = 0.709; p < 0.05) after exercise in HH. Conclusions: Both acute NH and HH altered hemodynamic and cerebral oxygenation and induced AMS. Subjects, who adapted their CI had higher rScO2 and lower LLS. Furthermore, rScO2 after exercise under normobaric conditions was associated with AMS at high altitudes.
Respiration Physiology, Sep 1, 1997
The fast initial increase in ventilation at the start of exercise is generally assumed to be of r... more The fast initial increase in ventilation at the start of exercise is generally assumed to be of reflex origin (exercising limbs) and/or caused by a 'feedforward' mechanism increasing breathing via brainstem respiratory centres or cortical areas controlling respiratory muscles. We wanted to test whether this ventilatory increase is in part a learned response which can be modified. Eleven subjects did two 20 min low-intensity arm-cranking exercise bouts on eight different days. Seven subjects were assigned to the experimental group which performed exercise paired with an 1.5 L external dead space. Before and after their eight exercise 'training'-days, these subjects did the same exercise without dead space. At the beginning of the first post-training exercise test (without dead space), the ventilatory increase at the start of exercise (sum of the first four breaths) was significantly increased (31.1 94.1 L • min − 1) compared to the pre-training test session (24.4 9 3.9 L • min − 1). No significant change was observed in the control group. We conclude that part of the ventilatory increase at the start of exercise can be modulated and might possibly be a learned response.
Muscle & Nerve, 2006
High-intensity exercise can induce diaphragm fatigue which can, in turn, limit exercise performan... more High-intensity exercise can induce diaphragm fatigue which can, in turn, limit exercise performance. We investigated whether expiratory muscles fatigue similarly during exhaustive exercise. Eleven healthy male volunteers cycled to exhaustion at 85% maximal power. Before, immediately after exercise, and after 30 and 60 min of recovery, the nerve roots supplying the abdominal muscles were stimulated magnetically at the T10 level in the prone position after full potentiation. Twitch gastric pressure (P ga,tw) was simultaneously recorded. After cycling, P ga,tw was significantly reduced compared to before exercise (40.2 Ϯ 6.6 vs. 45.3 Ϯ 7.5 cmH 2 O; P Ͻ 0.001), whereas after 30 and 60 min of recovery differences were no longer significant. The reduction in P ga,tw directly after exercise correlated neither with the fitness level nor with abdominal muscle work, respiratory sensations, or blood lactate concentration during exercise. These results indicate that the ventilatory requirements during intensive exercise can impair abdominal muscle contractility similar to diaphragmatic contractility. Thus, abdominal muscle fatigue may also contribute to exercise limitation, especially when expiratory resistance is increased as in patients with chronic obstructive pulmonary disease.
The Journal of Experimental Biology, Dec 15, 2002
Sports Medicine, Feb 1, 2019
Forest plots Electronic Supplementary Material Figure S1 Forest plot comparing total sleep time a... more Forest plots Electronic Supplementary Material Figure S1 Forest plot comparing total sleep time after evening exercise vs. control. Effect sizes are differences in means in minutes; positive values represent higher total sleep time after evening exercise compared to control. The last row with the black diamond represents the pooled data. d50_30, 30 min at an intensity 50% above the first ventilatory threshold; d50_60, 60 min at an intensity 50% above the first ventilatory threshold; DIS, difficulty initiating sleep; EMA, early morning awakenings; ModInt, moderate intensity; HighInt, high intensity; LowInt, low intensity; VT1_30, 30 min at the first ventilatory threshold; VT1_60, 60 min at the first ventilatory threshold
Sports Medicine, Jul 12, 2013
Sports Medicine, Aug 1, 2012
Objectives: Two distinct types of specific respiratory muscle training (RMT), i.e. respiratory mu... more Objectives: Two distinct types of specific respiratory muscle training (RMT), i.e. respiratory muscle strength (resistive/threshold) and endurance (hyperpnoea) training, have been established to improve the endurance performance of healthy individuals. We performed a systematic review and meta-analysis in order to determine the factors that affect the change in endurance performance after RMT in healthy subjects. Data sources: A computerized search was performed without language restriction in MEDLINE, EMBASE and CINAHL and references of original studies and reviews were searched for further relevant studies. Review methods: RMT studies with healthy individuals assessing changes in endurance exercise performance by maximal tests (constant load, time trial, intermittent incremental, conventional [non-intermittent] incremental) were screened and abstracted by two independent investigators. A multiple linear regression model was used to identify effects of subjects' fitness, type of RMT (inspiratory or combined inspiratory/expiratory muscle strength training, respiratory muscle endurance training), type of exercise test, test duration and type of sport (rowing, running, swimming, cycling) on changes in performance after RMT. In addition, a meta-analysis was performed to determine the effect of RMT on endurance performance in those studies providing the necessary data. Results: The multiple linear regression analysis including 46 original studies revealed that less fit subjects benefit more from RMT than highly trained athletes (6.0% per 10 mL Á kg-1 Á min-1 decrease in maximal oxygen uptake, 95% confidence interval [CI] 1.8, 10.2%; p = 0.005) and that improvements do not differ significantly between inspiratory muscle strength and respiratory
Respiration Physiology, Oct 1, 1998
Breathlessness arises from increased medullary respiratory center activity projecting to the fore... more Breathlessness arises from increased medullary respiratory center activity projecting to the forebrain (respiratory corollary discharge hypothesis). Subjects with congenital central hypoventilation syndrome (CCHS) lack the normal hyperpnea and breathlessness during hypercapnia. The corollary discharge hypothesis predicts that if CCHS subjects have normal hyperpnea during exercise, they will experience normal breathlessness during exercise. To test this, we studied four CCHS subjects and six matched controls during an exhausting constant-load cycling test requiring substantial anaerobiosis. CCHS subjects rated significantly less breathlessness at the end of the test than controls, but ventilation (index of respiratory corollary discharge) was also somewhat lower in CCHS (not significant). In both groups, breathlessness increased disproportionately more than ventilation towards the end of exercise. These data failed to disprove the corollary discharge hypothesis of breathlessness, but do suggest that the relationship between ventilation and breathlessness is non-linear and/or that projections of chemoreceptor afferents to the forebrain (presumed lacking in CCHS) is one source of breathlessness in normals.
American Journal of Respiratory and Critical Care Medicine, Apr 1, 2000
Journal of Science and Medicine in Sport, Mar 1, 2023
Diabetologie Und Stoffwechsel, Apr 1, 2018
Ziel Sowohl schwere Formen der Adipositas als auch des Typ-2-Diabetes (T2DM) gehen mit einer verr... more Ziel Sowohl schwere Formen der Adipositas als auch des Typ-2-Diabetes (T2DM) gehen mit einer verringerten Lungenfunktion und einer schlechteren kardiorespiratorischen Fitness einher. Wir untersuchten, ob das zusätzliche Vorliegen einer T2DM-Erkrankung die bereits beeinträchtigte Lungenfunktion und kardiorespiratorische Fitness bei Personen mit schwerer Adipositas weiter limitiert. Methoden In dieser Querschnittsstudie wurde die Lungenfunktion (Einsekundenkapazität FEV 1 ; Vitalkapazität, VC) bei 65 Probanden mit schwerer Adipositas und T2DM (T2DM-Gruppe) und 65 schwer adipösen Personen ohne T2DM (Nicht-T2DM-Gruppe), die paarweise nach Geschlecht, Alter, Körpermasse und-größe zugeordent wurden, bestimmt. Bei 30 dieser gematchten Paare wurde die kardiorespiratorische Fitness (maximale Leistung, W peak , maximale Sauerstoffaufnahme, V O 2peak) im Fahrrad-Stufentest ermittelt. * gleichberechtigte Autorenschaft.
Springer eBooks, 1996
Different studies have shown that the respiratory system can limit exercise performance. The maxi... more Different studies have shown that the respiratory system can limit exercise performance. The maximal duration of exercise at 90–95% of maximal work capacity (Wmax) was reduced in subjects who had fatigued their respiratory muscles just prior to the exercise test by either breathing against an inspiratory load (8) or by hyperventilating at 66% of their maximal voluntary ventilation (MVV) for 150 min (9). Respiratory endurance training in turn increased exercise duration at 64% of peak oxygen consumption (VO2) in sedentary subjects (2) and at 77% VO2,peak in trained subjects (1), whereas exercise duration at 90–95% Wmax was the same as before respiratory training (5, 10). These conflicting results with respect to improvement of endurance by respiratory training may result either from different workloads at which subjects were exercising or from different respiratory training regimes. For example, subjects breathing against resistance can improve respiratory muscle strength whereas subjects performing isocapnic hyperpnea increase respiratory endurance (7). It also seems possible that the specific breathing pattern adopted during the respiratory training could influence the pattern adopted during subsequent exercise. This would be of importance because breathing slowly and deeply is more efficient than rapid shallow breathing during exercise.
Physiology, Apr 1, 2000
I t is well accepted that the respiratory system may limit exercise performance in disease, e.g.,... more I t is well accepted that the respiratory system may limit exercise performance in disease, e.g., pulmonary or cardiovascular disease, but to what extent the respiratory system may play a significant role in limiting exercise performance of healthy subjects is still controversial. Different studies indicate that exercise does induce respiratory muscle fatigue (6, 9), that respiratory muscle fatigue can limit exercise performance (8, 10), that endurance of respiratory muscles can be trained (1-3, 11-13), and that respiratory endurance training can enhance endurance (but not peak) exercise performance (1, 2, 12, 13), even in healthy subjects. Changes in breathing pattern that occur with increasing exercise duration, possibly as a consequence of respiratory muscle fatigue, i.e., increased respiratory frequency, hyperventilation, and/or increased sense of respiratory effort, are reversed after respiratory endurance training, i.e., these changes are delayed or absent.
Frontiers in Physiology, 2020
Erythropoietin (EPO) boosts exercise performance through increase in oxygen transport capacity fo... more Erythropoietin (EPO) boosts exercise performance through increase in oxygen transport capacity following regular administration of EPO but preclinical study results suggest that single high dose of EPO also may improve exercise capacity. Twenty-nine healthy subjects (14 males/15 females; age: 25 ± 3 years) were included in a randomized, double-blind, placebo-controlled crossover study to assess peak work load and cardiopulmonary variables during submaximal and maximal cycling tests following a single dose of 60.000 IU of recombinant erythropoietin (EPO) or placebo (PLA). Submaximal exercise at 40%/60% of peak work load revealed no main effect of EPO on oxygen uptake (27.9 ± 8.7 ml min −1 •kg −1 / 37.1 ± 13.2 ml min −1 •kg −1) versus PLA (25.2 ± 3.7 ml min −1 •kg −1 / 33.1 ± 5.3 ml min −1 •kg −1) condition (p = 0.447/p = 0.756). During maximal exercise peak work load (PLA: 3.5 ± 0.6 W•kg −1 vs. EPO: 3.5 ± 0.6 W kg −1 , p = 0.892) and peak oxygen uptake (PLA: 45.1 ± 10.4 ml•min −1 kg −1 vs. EPO: 46.1 ± 14.2 ml•min −1 kg −1 , p = 0.344) reached comparable values in the two treatment conditions. Other cardiopulmonary variables (ventilation, cardiac output, heart rate) also reached similar levels in the two treatment conditions. An interaction effect was found between treatment condition and sex resulting in higher peak oxygen consumption (p = 0.048) and ventilation (p = 0.044) in EPO-treated males. In conclusion, in a carefully conducted study using placebo-controlled design the present data failed to support the hypothesis that a single high dose of EPO has a measurable impact on work capacity in healthy subjects.
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Papers by Christina Spengler