Papers by David Pendergast
European Journal of Applied Physiology, Mar 25, 2011
The aim of this paper was to develop a model from experimental data allowing a prediction of the ... more The aim of this paper was to develop a model from experimental data allowing a prediction of the cardiopulmonary responses to steady-state submaximal exercise in varying gravitational environments, with acceleration in the G z axis (a g ) ranging from 0 to 3 g. To this aim, we combined data from three different experiments, carried out at Buffalo, at Stockholm and inside the Mir Station. Oxygen consumption, as expected, increased linearly with a g . In contrast, heart rate increased non-linearly with a g , whereas stroke volume decreased non-linearly: both were described by quadratic functions. Thus, the relationship between cardiac output and a g was described by a fourth power regression equation. Mean arterial pressure increased with a g non linearly, a relation that we interpolated again with a quadratic function. Thus, total peripheral resistance varied linearly with a g . These data led to predict that maximal oxygen consumption would decrease drastically as a g is increased. Maximal oxygen consumption would become equal to resting oxygen consumption when a g is around 4.5 g, thus indicating the practical impossibility for humans to stay and work on the biggest Planets of the Solar System.
Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc
Propulsion in water requires a propulsive force to overcome drag. Male subjects were measured for... more Propulsion in water requires a propulsive force to overcome drag. Male subjects were measured for cycle frequency, energy cost and drag (D) as a function of velocity (V), up to maximal V, for fin and front crawl swimming, kayaking and rowing. The locomotion with the largest propulsive arms and longest hulls traveled the greatest distance per cycle (d/c) and reached higher maximal V. D while locomotoring increased as a function of V, with lower levels for kayaking and rowing at lower Vs. For Vs below 1 m/s, pressure D dominated, while friction D dominated up to 3 m/s, after which wave D dominated total D. Sport training reduced the D, increased d/c, and thus lowered C and increased maximal V. Maximal powers and responses to training were similar in all types of locomotion. To minimize C or maximize V, D has to be minimized by tailoring D type (friction, pressure or wave) to the form of locomotion and velocity.
European Journal of Applied Physiology, 2003
In this paper a complete energy balance for water locomotion is attempted with the aim of compari... more In this paper a complete energy balance for water locomotion is attempted with the aim of comparing different modes of transport in the aquatic environment (swimming underwater with SCUBA diving equipment, swimming at the surface: leg kicking and front crawl, kayaking and rowing). On the basis of the values of metabolic power (E _), of the power needed to overcome water resistance (W _ d) and of propelling efficiency (g P =W _ d /W _ tot , where W _ tot is the total mechanical power) as reported in the literature for each of these forms of locomotion, the energy cost per unit distance (C=E_/v, where v is the velocity), the drag (performance) efficiency (g d =W _ d /E _) and the overall efficiency (g o =W _ tot /E _=g d /g P) were calculated. As previously found for human locomotion on land, for a given metabolic power (e.g. 0.5 kW=1.43 lAEmin)1 V_O 2) the decrease in C (from 0.88 kJAEm)1 in SCUBA diving to 0.22 kJAEm)1 in rowing) is associated with an increase in the speed of locomotion (from 0.6 mAEs)1 in SCUBA diving to 2.4 mAEs)1 in rowing). At variance with locomotion on land, however, the decrease in C is associated with an increase, rather than a decrease, of the total mechanical work per unit distance (W tot , kJAEm)1). This is made possible by the increase of the overall efficiency of locomotion (g o =W_ tot /E _=W tot /C) from the slow speeds (and loads) of swimming to the high speeds (and loads) attainable with hulls and boats (from 0.10 in SCUBA diving to 0.29 in rowing).
Lungs and Breathing, 2017
Exercise capacity is decreased in submersion and depth. A possible explanation for this is an inc... more Exercise capacity is decreased in submersion and depth. A possible explanation for this is an increase in the work of breathing (WOB) due to increased effort to move the chest, increased breathing resistance, and increased gas density. WOB has been measured by the esophageal balloon technique, although this method does not measure alveolar pressure. One purpose of the present study was to test a modification of the P .1 interrupter technique that measures alveolar pressure (P A ) based on mouth pressure after a rapid interruption of flow by insertion of a wedge in the air supply as an alternative method of quantifying WOB and WOB per minute (POB) in the diving environment. A second purpose was to use this method to determine WOB submersed and at pressure. It was hypothesized that both submersion and depth would increase the WOB and POB. P A -volume loops were generated based on the P .1 method and WOB and POB calculated for both rest and exercise in 10 healthy male subjects during submersion and at depth. These results were compared to control conditions. Ventilation was increased in submersion, but was not significantly affected by depth. POB was found to be significantly increased in submersion, and further increased as a function of depth. The increased POB in these conditions were observed both at rest and during exercise, both during inspiration and expiration. The POB determined by the P .1 interrupter technique confirmed previous studies that used the esophageal balloon technique, with accurate determination of alveolar pressure and pressure-volume loops.
Sinoaortic contribution to ventilatory control in exercising dogs
Journal of Applied Physiology, 1983
The role of the sinoaortic reflexes in the regulation of ventilation during exercise was evaluate... more The role of the sinoaortic reflexes in the regulation of ventilation during exercise was evaluated in seven awake dogs prepared with chronic tracheostomies and arterial catheters. Each dog ran on a treadmill at several work loads before and after sinoaortic denervation and served as its own control. Minute ventilation in the sinoaortic denervated state was significantly reduced from intact values by 10–40% at the mild and moderate levels of exercise [O2 uptake (VO2) = 30–50 ml . kg-1 . min-1] mainly as a result of a lowering respiratory frequency. At higher work loads (VO2 = 70–80 ml . kg-1 . min-1) minute ventilation was similar in the intact and denervated states, but the pattern of ventilation was altered with a higher frequency and a lower tidal volume in the denervated state. The rise in ventilation toward a stable plateau was slower at all work loads in the denervated than in the intact state. After sinoaortic denervation, arterial PCO2(PaCO2) levels were significantly elevate...
Journal of Applied Physiology, 1995
VIII International Symposium on Biomechanics and Medicine in Swimming Presentation - July 1998
BioMed Research International, 2013
This study aimed to determine the relative contribution of selected biomechanical, energetic, coo... more This study aimed to determine the relative contribution of selected biomechanical, energetic, coordinative, and muscular factors for the 200 m front crawl and each of its four laps. Ten swimmers performed a 200 m front crawl swim, as well as 50, 100, and 150 m at the 200 m pace. Biomechanical, energetic, coordinative, and muscular factors were assessed during the 200 m swim. Multiple linear regression analysis was used to identify the weight of the factors to the performance. For each lap, the contributions to the 200 m performance were 17.6, 21.1, 18.4, and 7.6% for stroke length, 16.1, 18.7, 32.1, and 3.2% for stroke rate, 11.2, 13.2, 6.8, and 5.7% for intracycle velocity variation inx, 9.7, 7.5, 1.3, and 5.4% for intracycle velocity variation iny, 17.8, 10.5, 2.0, and 6.4% for propelling efficiency, 4.5, 5.8, 10.9, and 23.7% for total energy expenditure, 10.1, 5.1, 8.3, and 23.7% for interarm coordination, 9.0, 6.2, 8.5, and 5.5% for muscular activity amplitude, and 3.9, 11.9, 11...
Sports Engineering, 2006
This study investigated the basic fluid mechanics associated with the hydrodynamic drag of a huma... more This study investigated the basic fluid mechanics associated with the hydrodynamic drag of a human. The components of drag (friction D SF , pressure D P and wave D W ) on a human swimmer were analysed by applying classical fluid dynamic fundamentals. General methods of reducing drag were considered and the most probable method identified, applied and tested on swimsuit hydrodynamic drag. This study employed turbulators, either one (upper back) or three (across the upper back, the chest and across the buttocks), that were compared to an identical full body suit with no turbulators. Male and female elite competitive swimmers (n = 7 each) were towed in an annular pool to determine passive drag at speeds from 0.4 to 2.2 m s -1 . The total drag was reduced by 11-12% by one turbulator and 13-16% by three turbulators. The total drag was decomposed into D SF , D P and D W to determine the mechanisms responsible for the reduced total drag by the turbulators. The presence of the turbulators did not significantly increase friction or wave drag; however, flow was attached to the body as there was a significant reduction in pressure drag (19-41%), with the greatest reduction being for three turbulators (chest, back, buttocks). This study demonstrated the importance of pressure drag in determining total drag at high human swimming speeds, and that drag reducing technology can significantly reduce it, in this case by appropriately sized and placed turbulators.
Medicine & Science in Sports & Exercise, 2004
Introduction: The drag (D) of seven (7) male swimmers wearing five (5) swimsuits was investigated... more Introduction: The drag (D) of seven (7) male swimmers wearing five (5) swimsuits was investigated. Methods: The drag was measured during passive surface tows at speeds from 0.2 up to 2.2 m•s Ϫ1 and during starts and push-offs. The swimsuits varied in body coverage from shoulder-to-ankle (SA), shoulder-to-knee (SK), waist-to-ankle (WA) and waist-to-knee (WK) and briefs (CS). Results: Differences in total drag among the suits were small, but significant. In terms of least drag at 2.2 m•s Ϫ1 , the swimsuits ranked: SK, SA, WA, WK and CS. The drag was decomposed into its pressure drag (D P), skin friction drag (D SF) and wave drag (D W) components using nonlinear regression and classical formulations for each drag component. The transition-to-turbulence Reynolds number and decreasing frontal area with speed were taken into account. The transition-to-turbulence Reynolds number location was found to be very close to the swimmers' "leading edge," i.e. the head. Flow was neither completely laminar, nor completely turbulent; but rather, it was transitional over most of the body. The D P contributed the most to drag at low speeds (Ͻ1.0 m•s Ϫ1) and D W the least at all speeds. D SF contributed the most at higher speeds for SA and SK suits, whereas D P and D W were reduced compared with the other suits. Conclusion: The decomposition of swimmer drag into D SF , D P and D W suggests that increasing D SF on the upper-body of a swimmer reduces D P and D W by tripping the boundary layer and attaching the flow to the body from the shoulder to the knees. It is possible that body suits that cover the torso and legs may reduce drag and improve performance of swimmers.
Journal of Applied Physiology, 2013
Submersion and increased pressure (depth) characterize the diving environment and may independent... more Submersion and increased pressure (depth) characterize the diving environment and may independently increase demand on the respiratory system. To quantify changes in respiratory mechanics, this study employed a unique protocol and techniques to measure, in a hyperbaric chamber, inspiratory and expiratory alveolar pressures (interrupter technique), inspiratory and expiratory resistance in the airways (RawI and RawE, esophageal balloon technique), nitric oxide elimination (thought to correlate with Raw), inspiratory and expiratory mechanical power of breathing, and the total energy cost of ventilation. Eight healthy adult men underwent experiments at 1, 2.7, and 4.6 atmospheres absolute (ATA) in dry and fully submersed conditions. Subjects rested, cycled on an ergometer at 100 W, and rested while voluntarily matching their ventilation to their own exercise hyperpnea (isocapnic simulated exercise ventilation). During isocapnic simulated exercise ventilation, increased O2 uptake (above ...
Heart rate variability during dynamic exercise in elderly males and females
European Journal of Applied Physiology, 2000
It has been proposed that cardiac control is altered in the elderly. Power spectral analysis of h... more It has been proposed that cardiac control is altered in the elderly. Power spectral analysis of heart rate variability (HRV) was performed on 12 male and 11 female elderly subjects (mean age 74 years) while at rest in supine and sitting positions, and at steady states during 5 min of exercise (35-95% peak oxygen consumption, VO2peak). There were no differences in power, measured as a percentage of the total of the high frequency peak (HF, centred at about 0.25 Hz; 13% in males vs 12% in females), low frequency peak (LF, centred at 0.09 Hz; 25% in males and 22% in females), and very low frequency component (VLF, at 0.03 Hz; 66% in males and 69% in females) between body positions at rest. There was no difference in spectral power between male and female subjects. Total power decreased as a function of oxygen consumption during exercise, LF% did not change up to about 14 ml x kg(-1) x min(-1) (40% and 80% VO2peak in males and females, respectively), then decreased towards minimal values in both genders. HF% power and central frequency increased linearly with metabolic demand, reaching higher values in male subjects than in female subjects at VO2peak, while VLF% remained unchanged. Thus, the power spectra components of HRV did not reflect the changes in autonomic activity that occur at increasing exercise intensities, confirming previous findings in young subjects, and indicated similar responses in both genders.
Medicine & Science in Sports & Exercise, 2002
Purpose: The effects of an intense 8-wk aerobic training program on cardiovascular responses at r... more Purpose: The effects of an intense 8-wk aerobic training program on cardiovascular responses at rest and during exercise, including heart rate variability (HRV) as an expression of autonomic modulation, were evaluated in subjects over 70 yr (mean: 73.9 Ϯ 3.5 yr). Methods: Before and after training in 7 men and 8 women: a) heart rate (HR), blood pressures (BPs), pulse pressure (PP), and oxygen uptake were measured at rest, during, and after exhausting incremental exercise; b) HRV power spectra were calculated at rest in supine and sitting, and during and after two submaximal constant loads (5 min). Power in low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, Ͼ0.15 Hz) bands were expressed as a percent of total power minus power Ͻ 0.04 Hz. Results: After training: a) at rest HR and HRV parameters (in both body positions) were unchanged, whereas BPs decreased; b) peak cycle resistance and oxygen consumption increased by 25% and 18%, respectively, but no change in maximal HR and BPs were found; c) during submaximal loads HR was unchanged at the same metabolic demand, whereas SBP and DBP were lower than before at low loads whereas PP was unchanged. LF power decreased and HF increased at oxygen uptakes above about 0.7 L•min Ϫ1 similarly before and after training; and d) recovery of all parameters was similar to pretraining and complete after 10 min Conclusions: The increase in exercise capacity without changes in cardiovascular parameters suggests that 8 wk of aerobic training augmented peripheral gas exchange but not delivery to muscle. The lack of effect on HRV indicates that the improvements in aerobic power and cardiac autonomic modulation, at least in subjects over 70 yr, are dissociated. Moreover, the metabolic demand seems to be the main factor for the changes in HRV power spectra that occur during exercise.
Total body fat oxidation is reduced in elderly individuals even after exercise training
The FASEB Journal
Effect of wetted surface area on friction, pressure, wave and total drag of a kayak
Sports biomechanics, Jan 21, 2017
Using theoretical principles, the components of drag (friction D, pressure D and wave D) of a sin... more Using theoretical principles, the components of drag (friction D, pressure D and wave D) of a single-seat kayak were analysed. The purpose was to examine the effect of changes in wetted surface area due to changes in kayaker's weight and the relative contribution of D, D and D to the total passive drag as function of velocity. The total passive drag values were based on experimental data collected in a single-seat kayak. Three different kayaker simulated weights were tested - 65, 75 and 85 kg. D was the drag component that contributed the greatest percentage (between 60 and 68% at 5.56 m/s the top velocity tested) to the total passive drag for all the velocities tested and simulated weights. D was the most affected by the increase in kayaker's simulated weight, mainly when comparing 65/75 to 85 kg. Results support the importance of a kayak design selection that minimises the kayak's drag for the individual weight of the kayaker. Also, the results suggest that the path fo...
The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0168), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Divers swimming efficiency as a function of buoyancy, swimming attitude, protective garments, breathing apparatus, swimming technique and fin type
Myopathy and Venous Insufficiency
Phlebology, 1987
Eighty patients with severe venous insufficiency, documented by history, physical examination, ve... more Eighty patients with severe venous insufficiency, documented by history, physical examination, venography, and venous pressures, underwent gastrocnemius muscle biopsy. Muscle specimens were analysed histologically and histochemically in order to define the nature of pathological muscle changes which occur in patients with long-standing venous insufficiency. For comparison, muscle specimens from unaffected extremities were analysed. Histological analysis of muscle specimens from affected limbs showed a variety of muscle changes, including type II fibre atrophy, muscle necrosis and regeneration, and denervation atrophy. Histochemical analysis using 31P nuclear magnetic resonance revealed depletion of muscle energy stores, including creatine phosphate, ATP, and ADP.
Frontiers in psychology, 2016
The aim of this study was to compare the non-linear properties of the four competitive swim strok... more The aim of this study was to compare the non-linear properties of the four competitive swim strokes. Sixty-eight swimmers performed a set of maximal 4 × 25 m using the four competitive swim strokes. The hip's speed-data as a function of time was collected with a speedo-meter. The speed fluctuation (dv), approximate entropy (ApEn) and the fractal dimension by Higuchi's method (D) were computed. Swimming data exhibited non-linear properties that were different among the four strokes (14.048 ≤ dv ≤ 39.722; 0.682 ≤ ApEn ≤ 1.025; 1.823 ≤ D ≤ 1.919). The ApEn showed the lowest value for front-crawl, followed by breaststroke, butterfly, and backstroke (P < 0.001). Fractal dimension and dv had the lowest values for front-crawl and backstroke, followed by butterfly and breaststroke (P < 0.001). It can be concluded that swimming data exhibits non-linear properties, which are different among the four competitive swimming strokes.
Uploads
Papers by David Pendergast