Low-speed Swimming Research Articles

Field swimming behavior in largemouth bass deviates from predictions based on economy and propulsive efficiency.

Locomotion is energetically expensive. This may create selection pressures that favor economical locomotor strategies, such as the adoption of low-cost speeds and efficient propulsive movements. For swimming fish, the energy expended to travel a unit distance, or cost of transport (COT), has a U-shaped relationship to speed. The relationship between propulsive kinematics and speed, summarized by the Strouhal number (St=fA/U, where f is tail beat frequency, A is tail tip amplitude in m and U is swimming speed in ms-1), allows for maximal propulsive efficiency where 0.2<St<0.4. Largemouth bass adopted field speeds that were generally below the range predicted to minimize their COT. This may reflect speed modulation to meet competing functional demands such as enabling effective prey detection and capture. St exceeded the optimal range for the lowest observed swimming speeds. Mechanical and physiological constraints may prevent adoption of efficient St during low-speed swimming.

Development of an Unmanned Hybrid Vehicle Using Artificial Pectoral Fins

AbstractAn unmanned vehicle has been developed for dual use as both an aircraft and a submersible. To achieve long-range emplacement of a highly maneuverable underwater asset to a target environment, the Flimmer (Flying-Swimmer) vehicle is designed for both high-speed flight and low-speed swimming. Building on previous research in bioinspired propulsion and control systems, the vehicle employs a unique set of artificial flapping fins for underwater maneuvering, which must be considered when evaluating the flight and water landing capabilities. This paper describes the computational analysis and experimental results for all three phases of vehicle operation—flight, landing, and swimming. Computational fluid dynamics simulation results predict aero- and hydrodynamic characteristics and demonstrate landing loads on and trajectory of the vehicle. Experimental data demonstrate flight and swimming performance and validate the computational results, and experimental testing of water landing provides a comparison with computations. Results and analyses of the Flimmer vehicle performance demonstrate the operational capabilities of an unmanned hybrid vehicle for long-range flight and low-speed swimming.

Fluid dynamics of the larval zebrafish pectoral fin and the role of fin bending in fluid transport

Larval zebrafish beat their pectoral fins during many behaviors including low-speed swimming and prey tracking; however, little is known about the functions of these fin movements. Previously, we found experimental support for the function of larval fins in mixing of fluid near the body, which may enhance respiration by diffusion of dissolved oxygen across the skin. Here we use computational fluid dynamics to analyze fluid flow due to the pectoral fin movement. The pectoral fins bend along their proximodistal axis during abduction (fin extension), but remain nearly rigid during adduction (fin flexion). We hypothesize that this asymmetry in bending is critical for fluid mixing near the body and test the effects of fin bending with our simulations. For normal fin beats, we observed similar flow patterns in simulations and experiments. Flow patterns showed fluid stretching and folding, indicative of mixing. When proximodistal bending was removed from fin motion, fins were less effective at transporting fluid in a posterior direction near the body surface, but lateral mixing of fluid near the body was unaffected. Our results suggest that fin bending enhances posterior transport of fluid along the body surface, which may act to aid respiration in combination with lateral stretching and folding of fluid.

The Effects of Low-Speed Swimming following Exhaustive Exercise on Metabolic Recovery and Swimming Performance in Brook Trout (Salvelinus fontinalis)

Experiments were conducted to determine whether low-speed swimming during recovery from exhaustive exercise improved both metabolic recovery and performance during a swimming challenge. For these experiments, brook trout were allowed to recover from exhaustive exercise for 2 h while swimming at 0, 0.5, 1.0, or 1.5 body length (BL) s(-1) or allowed to recover from exhaustive exercise for 1, 2, or 3 h while swimming at 1.0 BL s(-1). At the appropriate interval, either (i) muscle and blood samples were removed from the fish or (ii) fish were assessed for performance (i.e., fatigue time) during a fixed-interval swimming test. Low-speed swimming during recovery from exhaustive exercise resulted in significantly longer fatigue times compared with fish recovering in still water (i.e., 0 BL s(-1)). However, swimming during recovery did not expedite recovery of muscle lactate or blood variables (e.g., lactate, osmolarity, glucose). These observations suggest that metabolic recovery and subsequent swimming performance may not be directly linked and that other factors play a role in swimming recovery in brook trout.

Exercise in Heart Failure: Should Aqua Therapy and Swimming Be Allowed?

Although exercise training is established as an integrated part of treatment regimes in both patients with transmural myocardial infarction (MI) and chronic congestive heart failure (CHF), there is no consensus yet on the appropriateness of water exercises and swimming. One reason is the lack of information concerning both central hemodynamic volume and pressure responses during immersion in these patients. This paper presents explorative studies on changes in cardiac dimensions and central hemodynamics during graded immersion and swimming in patients with moderate and/or severe MI and in patients with moderate and/or compensated severe CHF. For comparison purposes, healthy subjects were assessed. Measurements were performed by using Swan-Ganz right heart catheterization, subxiphoidal echocardiography, and Doppler-echocardiography. The major findings were: 1) Indicators of an increase in preload were seen in patients with moderate and severe MI. In both patient groups, upright immersion to the neck and supine body position at rest in the water resulted in abnormal mean pulmonary artery pressure (PAm) and mean pulmonary capillary pressures (PCPm), respectively. During low-speed swimming (20-25 m.min(-1)), the PAm and/or PCPm were higher than during supine cycle ergometry at a load of 100 W. 2) Left ventricular overload and decrease and/or no change in stroke volume occurred in patients with severe CHF who were immersed up to the neck. 3) Patient's well-being was maintained despite hemodynamic deterioration. The acute responses during immersion and swimming suggest the need for additional studies on long-term changes in cardiac dimensions and central hemodynamic in both patients with severe MI and severe CHF who undergo a swimming program, compared with nonswimming patients with MI and CHF of similar etiology and severity of disease.

The kinematics and performance of escape responses of the knifefish Xenomystus nigri

The kinematics and performance of the escape responses of the knifefish Xenomystus nigri, a fish specialized for low-speed, undulatory median-fin propulsion, were recorded by means of high-speed cinematography. Two types of escape were observed, one involving the formation of a C-shape along the longitudinal axis of the fish (stage 1), followed by a slow recoil of the body (single bend); the other (double bend) involved stage 1 followed by a contralateral bend (stage 2). The pectoral fins were extended throughout escapes of both types. The average maximum acceleration for double bend escapes was 127.98 m∙s−2; acceleration was usually greatest in stage 1. In double bend escapes, turning angles for stages 1 and 2 were not correlated. Pitch and roll orientations change during escapes. In stage 1, the average roll and average pitch were linearly correlated, suggesting that roll was partly responsible for establishing pitch. Knifefish achieved high maximum acceleration relative to other fish. Therefore, performance was not compromised by morphological specialization for low-speed swimming; however, a negative correlation of pitch with acceleration in stage 1 suggested that escapes involve a trade-off between acceleration and confusing a predator by changing planar orientation.

The Kinematics and Performance of the Escape Response in the Angelfish(Pterophyllum Eimekei)

ABSTRACTThe kinematics of turning manoeuvres and the distance-time performance in escape responses of startled angelfish (Pterophyllum eimekei) are investigated employing high-speed cinematography (400Hz). All escape responses observed are C-type fast-starts, in which the fish assumes a C shape at the end of the initial body contraction (stage 1). Kinematic analysis of the subsequent stage (stage 2) allows the response to be classified into two types: single bend (SB), in which the tail does not recoil completely after the formation of the C, and double bend (DB), in which it does.The two types of response have different total escape angles (measured from the subsequent positions of the centre of mass, SB 120·0°; DB 73·3°, P&amp;lt;0·005), different stage 2 turning angles (in the same direction as stage 1 for SB, 11·0°; in the direction opposite to stage 1 for DB, –21·9°: P&amp;lt;0·0005) and different maximum angular velocities in the direction opposite to the initial one (SB –8·08 rads−1; DB –56.62rads−1: P&amp;lt;0·001). There are no significant differences in stage 1 kinematics for the two types of escape. Stage 1 turning angle is linearly correlated to stage 2 turning angle for DB only (P&amp;lt;0·0l; r2=0·60) and to total escape angle for both types of response (P&amp;lt;0·000l; r2=0·80). Stage 1 duration is linearly correlated to stage 1 turning angle (P&amp;lt;0.0001; r2=0.83) and to total escape angle (P&amp;lt;0·0001; =0·72) for both types of escape.Distance-time performance is also different in the two response types, mainly because of differences in stage 2 (maximum velocity for SB 0&amp;lt;99ms−1; maximum velocity for DB 1·53ms−1: maximum acceleration for SB 34&amp;lt;1ms−2; maximum acceleration for DB 74&amp;lt;7 ms−2: P&amp;lt;0·000l in both cases). As a result, there are significant differences in the performance throughout the whole response (maximum velocity 1&amp;lt;02 ms−1 and 1&amp;lt;53 ms−1 for SB and DB fast-starts, respectively; maximum acceleration 63&amp;lt;2 ms−2 and 91&amp;lt;9 ms−2 for SB and DB fast-starts, respectively) as well as within a fixed time (0&amp;lt;03 s). Overall, higher distance-time performances associated with smaller angles of turn are found in DB than in SB responses. Comparison with previous studies reveals that angelfish have a good fast-start performance despite specializations for low-speed swimming. In addition, the angelfish turning radius (0·065 ±0·0063L, where L is body length; mean±2s.E.) is lower than that previously reported for any fish.

Starvation Effects on Protein Synthesis in Red and White Muscle of the Barred Sand Bass,Paralabrax nebulifer

Starvation of the fish Paralabrax nebulifer was accompanied by complex changes in the synthesis rates of different classes of proteins within the white muscle. Synthesis of white-muscle myofibrillar proteins, as measured by incorporation of 14C-leucine, decreased rapidly during starvation, whereas synthesis of total sarcoplasmic proteins was unchanged. Although actin and aldolase label incorporation in white muscle underwent an immediate decrease to approximately 10% of control, lactate dehydrogenase and creatine phosphokinase showed a smaller initial decrease. Relative activities of white-muscle glycolytic enzymes were conserved despite a significant loss in overall glycolytic capacity. Control of specific synthesis rates may be important in maintaining an overall balance of proteins with different half-lives. In red muscle, starvation led to no reductions in the synthesis of any protein examined. Changes in muscle protein synthesis rates were reflected in a larger decrease in RNA/DNA ratio in white muscle than in red muscle during starvation. These results suggest that balanced metabolic function is retained during starvation in fishes, and that starvation may have differential effects on high- and low-speed swimming abilities.