Sigrid Theunissen | Haute Ecole Paul-Henri Spaak (original) (raw)

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Papers by Sigrid Theunissen

OBJECTIVE: Scuba and breath-hold divers are compared to investigate whether endothelial response ... more OBJECTIVE: Scuba and breath-hold divers are compared to investigate whether endothelial response changes are similar despite different exposure(s) to hyperoxia. DESIGN: 14 divers (nine scuba and five breath-holding) performed either one scuba dive (25m/25 minutes) or successive breath-hold dives at a depth of 20 meters, adding up to 25 minutes of immersion time in a diving pool. Flow-mediated dilation (FMD)

Preventive measures for reducing the risk of decompression sickness (DCS) are based on the limita... more Preventive measures for reducing the risk of decompression sickness (DCS) are based on the limitation of diver-specific risk factors and the influence of determining factors during and after the dive such as dive duration and depth, ascent protocol, ambient temperature or exercising. Unfortunately, clinical data to support the importance and the definite role of each factor on DCS development are lacking due in part to the great inter/intra-variability between individuals regarding susceptibility to DCS.

European journal of applied physiology, Jan 26, 2015

The purpose of this study was (1) to further explore the heart rate dynamics and assess a potenti... more The purpose of this study was (1) to further explore the heart rate dynamics and assess a potential cardiovascular risk in response to 4000 m jumps in experienced skydivers; (2) to assess whether there is an impact of such jumps on skydivers' cortical arousal or not, which may impact their decision making processes. 18 experienced skydivers performed successive jumps from a plane at 4000 m of height. Heart rate dynamics and cortical arousal were assessed by the use of heart rate variability and Critical Flicker Fusion Frequency (CFFF), respectively. CFFF did not differ between the three measurement time points (p > 0.05). Mean heart rate increased during the jump (p < 0.001) and came back to pre-jump values after the jump (p < 0.001). Percentage of the differences of successive NN intervals greater than 50 ms (pNN50) decreased during the jump (p < 0.001) and kept lower values after the jump compared to pre-jump (p < 0.05). High-frequency power (HF) did not differ ...

Diving and hyperbaric medicine, 2013

Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia foll... more Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia followed by hypoxia and a build-up of carbon dioxide (CO₂), chest-wall compression and significant haemodynamic changes. This study analyses variations in plasma oxidative stress markers after a series of repetitive breath-hold dives. Thirteen breath-hold divers were asked to perform repetitive breath-hold dives to 20 metres' depth to a cumulative breath-hold time of approximately 20 minutes over an hour in the open sea. Plasma nitric oxide (NO), peroxinitrites (ONOO⁻) and thiols (R-SH) were measured before and after the dive sequence. Circulating NO significantly increased after successive breath-hold dives (169.1 ± 58.26% of pre-dive values; P = 0.0002). Peroxinitrites doubled after the dives (207.2 ± 78.31% of pre-dive values; P = 0.0012). Thiols were significantly reduced (69.88 ± 19.23% of pre-dive values; P = 0.0002). NO may be produced by physical effort during breath-hold diving....

The Journal of sports medicine and physical fitness, 2013

Our study's aim is to show how a five-week stretch training protocol, based on passive stretc... more Our study's aim is to show how a five-week stretch training protocol, based on passive stretching, can change muscle performance during a drop jump (stretch shortening cycle). This study observes in 8 healthy subjects (four males and four females), the effect of a 5-week passive stretch training protocol on the stretch shortening cycle (SSC) during the performance of a drop jump, and identify the architectural changes in the muscle. Subjects underwent measurements of their drop jump performance 3 times before, and 3 times after, the stretch training protocol. For the muscle tendon unit (MTU), changes were measured using the Hawkins and Hull's model. In order to calculate the length changes in the MTU, we measured the ankle and knee angles. For changes in the fascicle, the pennation angle and the thickness of the gastrocnemius medialis (GM) muscle were measured. After the 5-week stretch training protocol, a significant increase in flexibility was observed in the fascicle duri...

Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc

Scuba and breath-hold divers are compared to investigate whether endothelial response changes are... more Scuba and breath-hold divers are compared to investigate whether endothelial response changes are similar despite different exposure(s) to hyperoxia. 14 divers (nine scuba and five breath-holding) performed either one scuba dive (25m/25 minutes) or successive breath-hold dives at a depth of 20 meters, adding up to 25 minutes of immersion time in a diving pool. Flow-mediated dilation (FMD) was measured using echography. Peripheral post-occlusion reactive hyperemia (PORH) was assessed by digital plethysmography and plasmatic nitric oxide (NO) concentration using a nitrate/nitrite colorimetric assay kit. The FMD decreased in both groups. PORH was reduced in scuba divers but increased in breath-hold divers. No difference in circulating NO was observed for the scuba group. Opposingly, an increase in circulating NO was observed for the breath-hold group. Some cardiovascular effects can be explained by interaction between NO and superoxide anion during both types of diving ending to less N...

Kinésithérapie, la Revue, 2010

Journal of Physiology and Biochemistry, 2013

We examined whether the improvement of impaired NO-dependent vasorelaxation by exercise training ... more We examined whether the improvement of impaired NO-dependent vasorelaxation by exercise training could be mediated through a BH 4 -dependent mechanism. Male spontaneously hypertensive rats (SHR, n020) and Wistar-Kyoto rats (WKY, n020) were trained (Tr) for 9 weeks on a treadmill and compared to age-matched sedentary animals (Sed). Endothelium-dependent vasorelaxation (EDV) was assessed with acetylcholine by measuring isometric tension in rings of femoral artery precontracted with 10 −5 M phenylephrine. EDV was impaired in SHR-Sed as compared to WKY-Sed (p 00.02). Training alone improved EDV in both WKY (p00.01) and SHR (p00.0001). Moreover, EDV was not different in trained SHR than in trained WKY (p00.934). Pretreatment of rings with L-NAME (50 μM) cancelled the difference in ACh-induced relaxation between all groups, suggesting that NO pathway is involved in these differences. The presence of 10 −5 M BH 4 in the organ bath significantly improved EDV for sedentary SHR (p00.030) but not WKY group (p00.815). Exercise training turned the beneficial effect of BH 4 on SHR to impairment of ACh-induced vasorelaxation in both SHR-Tr (p00.01) and WKY-Tr groups (p00.04). These results suggest that beneficial effect of exercise training on endothelial function is due partly to a BH 4dependent mechanism in established hypertension.

European Journal of Applied Physiology, 2013

Objective The aim of this study is to observe the effects of dark chocolate on endothelial functi... more Objective The aim of this study is to observe the effects of dark chocolate on endothelial function after a series of successive apnea dives in non-thermoneutral water. Methods Twenty breath-hold divers were divided into two groups: a control group (8 males and 2 females) and a chocolate group (9 males and 1 female). The control group was asked to perform a series of dives to 20 m adding up to 20 min in the quiet diving pool of Conflans-Ste-Honorine (Paris, France), water temperature was 27°C. The chocolate group performed the dives 1 h after ingestion of 30 g of dark chocolate. Flow-mediated dilatation (FMD), digital photoplethysmography, nitric oxide (NO), and peroxynitrite ONOO -) levels were measured before and after each series of breath-hold dives. Results A significant decrease in FMD was observed in the control group after the dives (95.28 ± 2.9 % of pre-dive values, p \ 0.001) while it was increased in the chocolate group (104.1 ± 2.9 % of pre-dive values, p \ 0.01). A decrease in the NO level was observed in the control group (86.76 ± 15.57 %, p \ 0.05) whereas no difference was shown in the chocolate group (98.44 ± 31.86 %, p [ 0.05). No differences in digital photoplethysmography and peroxynitrites were observed between before and after the dives. Conclusion Antioxidants contained in dark chocolate scavenge free radicals produced during breath-hold diving. Ingestion of 30 g of dark chocolate 1 h before the dive can thus prevent endothelial dysfunction which can be observed after a series of breath-hold dives.

Diving and hyperbaric medicine, 2015

The aim of the study was to observe the effects of dark chocolate on endothelial function after s... more The aim of the study was to observe the effects of dark chocolate on endothelial function after scuba diving. Forty-two male scuba divers were divided into two groups: a control (n = 21) and a chocolate group (n = 21). They performed a 33-metres deep scuba-air dive for 20 minutes in a diving pool (Nemo 33, Brussels). Water temperature was 33⁰C. The chocolate group ingested 30 g of dark chocolate (86% cocoa) 90 minutes before the dive. Flow-mediated dilatation (FMD), digital photoplethysmography and nitric oxide (NO) and peroxynitrites (ONOO-) levels were measured before and after the scuba dive in both groups. A significant decrease in FMD was observed in the control group after the dive (91 ± 7% (mean ± 95% confidence interval) of pre-dive values; P < 0.001) while it was increased in the chocolate group (105 ± 5% of pre-dive values; P < 0.001). No difference in digital photoplethysmography was observed between before and after the dives. No variation of circulating NO level w...