Cardiovascular Responses to Simultaneous Diving and Muscle Metaboreflex Activation

Background: The aim of study was to assess hemodynamic changes during the simultaneous activation of muscle metaboreflex (MM) and diving reflex (DR) in a laboratory setting. We hypothesized that as long as the exercise intensity is mild DR can overwhelm the MM.Methods: Ten trained divers underwent all four phases (randomly assigned) of the following protocol. (A) Postexercise muscle ischemia session (PEMI): 3 min of resting followed by 3 min of handgrip at 30% of maximum force, followed immediately by 3 min of PEMI on the same arm induced by inflating a sphygmomanometer. Three minutes of recovery was further allowed after the cuff was deflated for a total of 6 min of recovery. (B) Control exercise recovery session: the same rest-exercise protocol used for A followed by 6 min of recovery without inflation. (C) DR session: the same rest-exercise protocol used for A followed by 1 min of breath-hold (BH) with face immersion in cold water. (D) PEMI-DR session: the same protocol used for A with 60 s of BH with face immersion in cold water during the first minute of PEMI. Stroke volume (SV), heart rate (HR), and cardiac output (CO) were collected by means of an impedance method.Results: At the end of apnea, HR was decreased in condition C and D with respect to A (−40.8 and −40.3%, respectively vs. −9.1%; p < 0.05). Since SV increase was less pronounced at the same time point (C = +32.4 and D = +21.7% vs. A = +6.0; p < 0.05), CO significantly decreased during C and D with respect to A (−23 and −29.0 vs. −1.4%, respectively; p < 0.05).Conclusion: Results addressed the hypothesis that DR overcame the MM in our setting.

Large Lung Volumes Delay the Onset of the Physiological Breaking Point During Simulated Diving

During breath holding after face immersion there develops an urge to breathe. The point that would initiate the termination of the breath hold, the “physiological breaking point,” is thought to be primarily due to changes in blood gases. However, we theorized that other factors, such as lung volume, also contributes significantly to terminating breath holds during face immersion. Accordingly, nine naïve subjects (controls) and seven underwater hockey players (divers) voluntarily initiated face immersions in room temperature water at Total Lung Capacity (TLC) and Functional Residual Capacity (FRC) after pre-breathing air, 100% O2, 15% O2 / 85% N2, or 5% CO2 / 95% O2. Heart rate (HR), arterial blood pressure (BP), end-tidal CO2 (etCO2), and breath hold durations (BHD) were monitored during all face immersions. The decrease in HR and increase in BP were not significantly different at the two lung volumes, although the increase in BP was usually greater at FRC. BHD was significantly longer at TLC (54 ± 2 s) than at FRC (30 ± 2 s). Also, with each pre-breathed gas BHD was always longer at TLC. We found no consistent etCO2 at which the breath holding terminated. BDHs were significantly longer in divers than in controls. We suggest that during breath holding with face immersion high lung volume acts directly within the brainstem to actively delay the attainment of the physiological breaking point, rather than acting indirectly as a sink to produce a slower build-up of PCO2.

Inducible torsades de pointes during an acute face immersion test in an adolescent with type 2 long QT syndrome

We present the case of a 12-year-old boy with type 2 long QT syndrome in whom torsades de pointes was induced by an acute face immersion test. This test is feasible to predict cardiac events in adolescents with long QT syndrome.

The acquisition of aquatic skills in preschool children: deep versus shallow water swimming lessons

One of the key factors in the swimming teaching-learning process seems to be the variation of water’s depth.However, there are almost no studies about this topic and the existing ones usually follow a basic approach and with no control of the educational program used. It was our purpose to determine the effect of deep versus shallow water differences on developing pre-schoolers’ aquatic skills after 6 months of practice. Twenty-one Portuguese school-aged children of both genders (4.70 ± 0.51 yrs.), inexperienced in aquatic programs, participated in this study. The children were divided into two groups performing a similar aquatic program but in a different water depth: shallow water (n=10) and deep water (n=11). Each participant was evaluated twice for their aquatic readiness using an observation check list of 17 aquatic motor skills: during the first session (T0) and after six months of practice (two sessions per week with a total of 48 sessions) (T1). The aquatic proficiency on each skill was compared between the groups and a stepwise discriminant analysis was conducted to predict the conditions with higher or lower aquatic competence. Results suggested that swimming practice contributed positively to improvements on several basic aquatic skills, in both groups. The results showed that shallow water group managed to acquire a higher degree of aquatic competence particularly in five basic aquatic skills (p< .05): breath control combined with face immersion and eye opening; horizontal buoyancy; body position at ventral gliding; body position at dorsal gliding; leg kick with breath control at ventral body position, without any flutter device. The discriminant function revealed a significant association between both groups and four included factors (aquatic skills) (p< .001), accounting for 88% between group variability. The body position at ventral gliding was the main relevant predictor (r=0.535). Shallow water swimming lessons generated greater aquatic competence in preschool children after a period of 6 months of practice.

A Time–Motion Analysis of Elite Solo Synchronized Swimming

Purpose:To determine the total amount and relative time periods of face immersion (FI) in a synchronized swimming solo routine and the relationship between FI, distance covered, and the technical-merit score of the 11 top Canadian soloists at a synchronized swimming national championship (mean age 20 ± 1.8 y, height 173.3 ± 4.1 cm, and body mass 58.3 ± 4 kg).Methods:Videotape and timing of solo performances combined with manual tracking of pool patterns.Results:Analysis of performance revealed that an average of 18 FI periods, mean of 6.8 s, were performed for an average total time of 133.7 ± 27.1 s (range 102.2 to 199.8 s). The average longest FI time period was 25.45 ± 6.2 s (range 18.18 to 38.72 s), and most (10/11) of these were in the first third of the solo. The mean total horizontal distance covered was 57.61 ± 6.84 m (range 48.61 to 68.2 m), and the total horizontal distance covered relative to time was 0.276 ± 0.034 m/s (range 0.235 to 0.340 m/s). No significant relationships were found between any of the FI periods and the distance covered or between the technical-merit score and FI periods. Each solo contained 6 to 8 underwater sequences, none of which were longer than 40 seconds, the cutoff deemed dangerous by FINA (Fédération Internationale de Natation).Conclusion:This study shows that the times underwater for solos in Canada are within safety limits recommended by FINA and that judging in Canada is not related to underwater periods of swimming.