The effect of exhaustive chasing training and detraining on swimming performance in juvenile darkbarbel catfish (Peltebagrus vachelli)

Continuous flow stimulation had no significant effect on the growth rate but was conducive to the swimming performance, spontaneous behavior, and nonspecific immune parameter of juvenile Percocypris pingi

Flow stimulation before release into the wild may contribute to improved survivability of farmed fish. However, the effects of flow stimulation on the survival rate of fish depend on the fish species and exercise regime, such as exercise type, duration, and intensity. In this study, juvenile Percocypris pingi swam for 18 h per day for 8 weeks under different water speeds, 3 cm s-1 (control) and 1, 2, and 4 body lengths (bl) s-1 , at 20°C. Then, parameters related to the growth rate, swimming capacity, spontaneous activity, and immune function were measured. We found that (1) continuous flow stimulation had no significant influence on the growth but was conducive to the increase in the relative carcass mass; (2) continuous flow stimulation at 2 or 4 bl s-1 enhanced the aerobic swimming capacity (Ucrit ), which may be due to an increase in anaerobic exercise capacity (endurance time) rather than to changes in maximum metabolic rate and aerobic scope; (3) continuous flow stimulation at 4 bl s-1 led to a significant increase in spontaneous activity, which was mainly due to the higher percent time spent moving as compared with the controls; and (4) continuous flow stimulation at 2 bl s-1 may contribute to improving the nonspecific immune parameter (lysozyme activity) in juvenile P. pingi. Our findings suggest that continuous flow stimulation at 2 or 4 bl s-1 for 18 h per day for 56 days at 20°C before release in wild may be a suitable training regime for improving the survival rate of cultured juvenile P. pingi.

Effects of Aerobic Exercise Training on the Growth, Swimming Performance, Antipredation Ability and Immune Parameters of Juvenile Rock Carp (Procypris rabaudi)

Many studies have found that aerobic exercise training at a moderate water velocity can improve the growth, swimming performance and survival rate of fish. To investigate the effects of aerobic exercise training on the growth, swimming performance, antipredation ability and immune parameters of rock carp, juveniles were placed in training channels with different water velocities (i.e., 3 cm s−1, 1 (body length s−1) bl s−1, 2 bl s−1 and 4 bl s−1) for 6 weeks. Then, the specific growth rate, critical swimming speed (Ucrit) and its metabolism, constant acceleration speed (Ucat), survival rate under predation, spleen index, lysozyme (LZM) activity and immunoglobulin (IgM) level were measured. Training showed no significant effect on the length-specific growth rate, weight-specific growth rate, Ucrit, maximum metabolic rate (MMR), metabolic scope (MS), Ucat or spleen index. The resting metabolic rates (RMRs) of the 2 bl s−1 and 4 bl s−1 training groups were significantly higher than those of the control group and 1 bl s−1 training group. The survival rate of the 1 bl s−1 training group in the presence of predators was significantly higher than that of the control group but significantly lower than those of the 2 bl s−1 and 4 bl s−1 training groups. The LZM activity of the 4 bl s−1 training group was significantly higher than that of the control group. The IgM level of the 2 bl s−1 training group was significantly higher than that of the control group. These data indicate that aerobic exercise training does not improve the growth and swimming performance of juvenile rock carp but can improve their antipredation ability and immunologic function.

Sustained swimming exercise training decreases the individual variation in the metabolic phenotype of gilthead sea bream (Sparus aurata)

Cultured fish can be induced to swim, although the suitability and benefits remain to be tested. Sustained swimming exercise (SSE) training and detraining (DET) were applied in juvenile gilthead sea bream (Sparus aurata) and the metabolic rates were investigated. Fish with a total body mass of 80.5 ± 1.5 g and total length 17.2 ± 0.1 cm were maintained untrained (spontaneously swimming activity, UNT), swim-trained (induced sustained swimming activity, SSE) at 1 BL s^-1 for 28 days, or detrained (28 days of swimming followed by 10 days of untraining, DET). Standard metabolic rate (SMR), maximum metabolic rate (MMR), and excess post-exercise oxygen consumption (EPOC) were assessed (n = 10). In addition, the effects of SSE training (51 days) on blood and plasma parameters were investigated before and immediately after applying a high-intensity swimming (HIS) protocol. SMR, MMR, and EPOC values were not different between SSE, UNT, or DET fish (143.2, 465.5 mg O₂ kg^-1 h^-1, and 459.1 mg O₂ kg^-1, respectively). Spite the lack of differences between treatments, the dispersion in the residuals for SMR, MMR, and absolute aerobic scope (AAS) values followed the order UNT > DET > SSE, indicating that swim training decreases the individual variation of these metabolic parameters. Haematological parameters, plasma glucose, lactate, and cortisol levels were similar between SSE and UNT groups before HIS. Plasma glucose and lactate levels increased in both groups after HIS, being higher in the SSE group. Plasma cortisol levels were similar between both groups after HIS. Results suggest that SSE training improves energy use and reduces individual variation in SMR and MMR, an effect that declines with detraining.

Improved aerobic and anaerobic swimming performance after exercise training and detraining in Schizothorax wangchiachii: Implications for fisheries releases

Swimming performance (aerobic and anaerobic) is often used to predict the ability of fish to adapt and survive. Fish raised in captivity are typically poor swimmers and have lower survival rates than wild conspecifics when released into the natural environment. We investigated the potential for exercise training to enhance the swimming performance of Schizothorax wangchiachii held in captivity. Juvenile fish (mean body mass 1.40 ± 0.13 g, mean body length 4.36 ± 0.24 cm) were trained under five different regimes [3 cm·s^-1 control group (C), 10 cm·s^-1 for 6 (L6) and 12 h (L12) per day and 20 cm·s^-1 for 6 (H6) and 12 h (H12) per day] for 30 days and then detrained for 20 days (i.e. no training). Aerobic (i.e. critical swimming speed, U_crit), anaerobic swimming performance (i.e. endurance time at 1.2 or 1.5 U_crit), and morphological parameters were measured at the beginning (T₀), after 30 days of exercise training (T₃₀) and after 20 days of detraining (DT₂₀). Aerobic exercise training significantly improved the U_crit, endurance time at 1.2 and 1.5 U_crit of juvenile S. wangchiachii (P < .05). After 20 days of detraining, both the aerobic and anaerobic swimming performance of the H6 and H12 groups declined and no longer differed from the control group indicating a failure to maintain improved swimming performance, whereas improved swimming performance was maintained in L6 and L12 groups. No significant difference in swimming performance was found between 6 and 12 hours training at 10 cm·s^-1. Thus, exercise at close to 10 cm·s^-1 for 6 h per day for 30 days or a longer time periods prior to release appears to be a suitable regime for swimming performance enhancement, potentially increasing survivability of released S. wangchiachii in wild.

Physiological Responses to Swimming-Induced Exercise in the Adult Zebrafish Regenerating Heart

Exercise promotes a set of physiological responses known to provide long-term health benefits and it can play an important role in cardioprotection. In the present study, we examined cardiac responses to exercise training in the adult zebrafish and in the context of cardiac regeneration. We found that swimming-induced exercise increased cardiomyocyte proliferation and that this response was also found under regenerating conditions, when exercise was performed either prior to and after ventricular cryoinjury (CI). Exercise prior to CI resulted in a mild improvement in cardiac function and lesion recovery over the non-exercise condition. Transcriptomic profiling of regenerating ventricles in cryoinjured fish subjected to exercise identified genes possibly involved in the cardioprotective effects of exercise and that could represent potential targets for heart regeneration strategies. Taken together, our results suggest that exercise constitutes a physiological stimulus that may help promote cardiomyogenic mechanisms of the vertebrate heart through the induction of cardiomyocyte proliferation. The zebrafish exercise model may be useful for investigating the potential cardioprotective effects of exercise in teleost fish and to contribute to further identify and develop novel avenues in basic research to promote heart regeneration.

Sustained exercise-trained juvenile black carp (Mylopharyngodon piceus) at a moderate water velocity exhibit improved aerobic swimming performance and increased postprandial metabolic responses

The objectives of this study were to examine whether sustained exercise training at four water velocities, i.e. nearly still water (control), 1 body length (BL) s-1, 2 BL s-1 and 4 BL s-1, has effects on swimming performance and digestive metabolism in juvenile black carp (Mylopharyngodon piceus). The results demonstrated that fish subjected to sustained training at 2 and 4 BL s-1 showed significantly higher critical swimming speed (Ucrit) and maximum metabolic rate (MMR) over the control group. Fish subjected to sustained training at 1 and 2 BL s-1 showed a significantly (30 and 54%) prolonged duration, 14 and 17% higher postprandial ṀO2 increment (i.e. ṀO2peak), and 62 and 92% more energy expended on specific dynamic action (SDA), respectively, after consuming a similar meal over fish kept in nearly still water. These results suggest that (1) sustained exercise training at a higher speed (2 or 4 BL s-1) had a positive influence on the aerobic swimming performance of juvenile M. piceus, which may be associated with improved aerobic metabolism; and (2) sustained exercise training at a lower speed (1 or 2 BL s-1) resulted in elevated postprandial metabolic responses in juvenile M. piceus.

The effect of prolonged exercise training on swimming performance and the underlying biochemical mechanisms in juvenile common carp (Cyprinus carpio)

To investigate the effect of prolonged exercise training on swimming performance and the underlying biochemical mechanisms in juvenile common carp (Cyprinus carpio), we measured the critical swimming speed (Ucrit), the excess post-exercise oxygen consumption (EPOC), the activity of red and white muscle enzymes [pyruvate kinase (PK), lactate dehydrogenase (LDH) and citrate synthase (CS)], the tissue substrates (glycogen and glucose content of muscle and liver) and metabolite (the lactate content of plasma and muscle) content of exercise-trained (60% Ucrit for 4 weeks) and non-trained fish. We also measured the biochemical indices of both trained and non-trained fish immediately after Ucrit, after exhaustive exercise and 1h after exhaustive exercise. The aerobic swimming performance, as indicated by Ucrit, increased significantly after exercise training, most likely because of the higher tissue metabolic capacity, as suggested by the higher CS activity in the red muscle tissue, and the higher energy store and more efficient substrate utilization, as suggested by higher liver and muscle glycogen contents at rest but lower tissue glycogen contents after Ucrit. The lower lactate content after Ucrit is most likely because of higher aerobic metabolic capacity, and (or) the clearance rate of lactate in trained fish may also contribute to improved aerobic swimming performance. Compared to Ucrit, exhaustive exercise elicited higher plasma and muscle lactate contents. The anaerobic metabolic performance is not affected by the exercise training, as suggested by the EPOC. However, trained fish did show higher lactate clearance rates, as suggested by lower muscle lactate content after a 1h recovery period following exhaustive exercise compared to non-trained fish. Furthermore, trained fish decreased their liver and muscle glycogen contents more profoundly after exhaustive exercise, suggesting that training can improve the substrate utilization during anaerobic exercise.

The effect of aerobic exercise training on growth performance, digestive enzyme activities and postprandial metabolic response in juvenile qingbo (Spinibarbus sinensis)

Continual swimming exercise usually promotes growth in fish at a moderate water velocity. We hypothesized that the improvement in growth in exercise-trained fish may be accompanied by increases in digestive enzyme activity, respiratory capacity and, hence, postprandial metabolism. Juvenile qingbo fish (Spinibarbus sinensis) were subjected to aerobic training for 8weeks at a water velocity of control (3cms(-1)), 1, 2 and 4 body length (bl)s(-1) at a constant temperature of 25°C. The feed intake (FI), food conversion rate (FCR), specific growth rate (SGR), whole-body composition, trypsin and lipase activities, maximal oxygen consumption (M˙O2max) and postprandial M˙O2 response were measured at the end of the training period. Aerobic exercise training induced a significant increase in FI compared with the control group, while the FCR of the 4bls(-1) group was significantly lower than for the other three groups (P<0.05). The 1 and 2bls(-1) groups showed a significantly higher SGR over the control group (P<0.05). The whole-body fat and protein contents were significantly altered after aerobic exercise training (P<0.05). Furthermore, aerobic exercise training elevated the activity of both trypsin and lipase in the hepatopancreas and intestinal tract of juvenile S. sinensis. The M˙O2max of the 4bls(-1) training group was significantly higher than for the control group. The resting M˙O2 (M˙O2rest) and peak postprandial M˙O2 (M˙O2peak) in the three training groups were significantly higher than in the control group (P<0.05). Time to M˙O2peak was significantly shorter in the 1, 2 and 4bls(-1) training groups compared with the control group, while exercise training showed no effect on SDA (specific dynamic action) duration, factorial metabolic scope, energy expended on SDA and the SDA coefficient when compared to the control group. These data suggest that (1) the optimum water velocity for the growth of juvenile S. sinensis occurred at approximately 2.4bls(-1); (2) the improvement of growth may have been primarily due to an increase in the FI after long-term training; (3) and aerobic exercise training boosted the activity of digestive enzymes and maximum digestive metabolism, which could favor fast digestion and growth in juvenile S. sinensis.

The effects of hypoxia acclimation, exercise training and fasting on swimming performance in juvenile qingbo (Spinibarbus sinensis)

To investigate the effects of hypoxia acclimation, exercise training and fasting on the swimming performance of juvenile qingbo (Spinibarbus sinensis), we measured the critical swimming speed (U (crit)), resting and excess post-exercise oxygen consumption (EPOC) of control, hypoxia-acclimated, exercise-acclimated and fasting fish at 25°C. The muscle and plasma metabolites before and after a bout of exhaustive exercise (produced by chasing) were also measured. The fish were acclimated to hypoxia (48 h at 1.0 mg L(-1), 12.5% air saturation), exercise training (2 weeks at 60% of U (crit), 6 h daily) or fasting (2 weeks). All treatments resulted in significantly lower resting oxygen consumption ([Formula: see text]O(2rest)) but had no effect on the magnitude of EPOC. Hypoxia acclimation had no effect on U (crit) or peak post-exercise oxygen consumption ([Formula: see text]O(2peak)) but produced a higher depletion of muscle [glycogen] post-chasing (P < 0.05). Exercise training produced a significant increase in U (crit), higher liver [glycogen] pre-chasing and higher depletion of muscle [glycogen] post-chasing. Fasting resulted in a significant decrease in U (crit), [Formula: see text]O(2peak), muscle and liver [glycogen]. These results suggested that hypoxia acclimation had no effect on swimming performance in qingbo. Exercise training produced improved swimming performance by increasing the stored energy and the metabolic capacity of muscle. Fasting had a profound effect on swimming performance through both decreased respiratory capacity and a depleted energy store.

The effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis)

To investigate the effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis), we measured the following: (1) the resting oxygen consumption rate \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{rest}}}} } \right) $$\end{document}, critical swimming speed (U_crit) and active oxygen consumption rate \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} } \right) $$\end{document} of fish at acclimation temperatures of 10, 15, 20, 25 and 30 °C and (2) the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $$\end{document}, U_crit and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$\end{document} of both exercise-trained (exhaustive chasing training for 14 days) and control fish at both low and high acclimation temperatures (15 and 25 °C). The relationship between U_crit and temperature (T) approximately followed a bell-shaped curve as temperature increased: U_crit = 8.21/{1 + [(T − 27.2)/17.0]²} (R² = 0.915, P < 0.001, N = 40). The optimal temperature for maximal U_crit (8.21 BL s⁻¹) in juvenile qingbo was 27.2 °C. Both the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$\end{document} and the metabolic scope (MS, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} - \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $$\end{document}) of qingbo increased with temperature from 10 to 25 °C (P < 0.05), but there were no significant differences between fish acclimated to 25 and 30 °C. The relationships between \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$\end{document} or MS and temperature were described as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} = 1,214.29/\left\{ {1 + \left[ {\left( {T - 28.8} \right)/10.6} \right]^{2} } \right\}\;\left( {R^{2} = 0.911,\;P < 0.001,\;N = 40} \right) $$\end{document} and MS = 972.67/{1 + [(T − 28.0)/9.34]²} (R² = 0.878, P < 0.001, N = 40). The optimal temperatures for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$\end{document} and MS in juvenile qingbo were 28.8 and 28.0 °C, respectively. Exercise training resulted in significant increases in both U_crit and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$\end{document} at a low temperature (P < 0.05), but training exhibited no significant effect on either U_crit or \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$\end{document} at a high temperature. These results suggest that exercise training had different effects on swimming performance at different temperatures. These differences may be related to changes in aerobic metabolic capability, arterial oxygen delivery, available dissolved oxygen, imbalances in ion fluxes and stimuli to remodel tissues with changes in temperature.

The effect of acclimation to hypoxia and sustained exercise on subsequent hypoxia tolerance and swimming performance in goldfish (Carassius auratus)

The objective of this study was to determine whether acclimation to hypoxia and sustained exercise would increase hypoxia tolerance (as indicated by a decrease in critical oxygen tension, Pcrit) and swimming performance in goldfish (Carassius auratus), and to investigate the relationship between changes in performance and gill remodelling and tissue metabolic capacity. Goldfish were acclimated to either hypoxia (48 h at 0.3 mg O2 l–1) or sustained exercise (48 h at 70% of critical swimming speed, Ucrit) and then Pcrit and Ucrit were determined in normoxia (10 mg O2 l–1) and hypoxia (1 mg O2 l–1) and compared with values from control fish. Acclimation to both hypoxia and sustained exercise improved hypoxia tolerance (Pcrit was reduced by 49% and 39%, respectively), which was associated with an increase in lamellar surface area (71% and 43%, respectively) and an increase in blood [Hb] (26% in both groups). Exercise acclimation also resulted in a decrease in routine (). Acclimation to both hypoxia and sustained exercise resulted in a significant increase in Ucrit in hypoxia (18% and 17%, respectively), which was associated with an increase in maximal O2 consumption rate at Ucrit (; 35% and 39%, respectively). While hypoxia acclimation resulted in an increase in Ucrit in normoxia, acclimation to sustained exercise did not improve subsequent swimming performance in normoxia. This lack of improvement was possibly due to depleted oxidizable substrates during exercise acclimation.

Exhaustive exercise training enhances aerobic capacity in American alligator (Alligator mississippiensis)

The oxygen transport system in mammals is extensively remodelled in response to repeated bouts of activity, but many reptiles appear to be ‘metabolically inflexible’ in response to exercise training. A recent report showed that estuarine crocodiles (Crocodylus porosus) increase their maximum metabolic rate in response to exhaustive treadmill training, and in the present study, we confirm this response in another crocodilian, American alligator (Alligator mississippiensis). We further specify the nature of the crocodilian training response by analysing effects of training on aerobic [citrate synthase (CS)] and anaerobic [lactate dehydrogenase (LDH)] enzyme activities in selected skeletal muscles, ventricular and skeletal muscle masses and haematocrit. Compared to sedentary control animals, alligators regularly trained for 15 months on a treadmill (run group) or in a flume (swim group) exhibited peak oxygen consumption rates higher by 27 and 16%, respectively. Run and swim exercise training significantly increased ventricular mass (~11%) and haematocrit (~11%), but not the mass of skeletal muscles. However, exercise training did not alter CS or LDH activities of skeletal muscles. Similar to mammals, alligators respond to exercise training by increasing convective oxygen transport mechanisms, specifically heart size (potentially greater stroke volume) and haematocrit (increased oxygen carrying-capacity of the blood). Unlike mammals, but similar to squamate reptiles, alligators do not also increase citrate synthase activity of the skeletal muscles in response to exercise.