## 1 Introduction  
Fatigue is one of the most common and disabling non-motor problems, which generally leads to negative effects on physical and cognitive function. Therefore, fatigue is best defined as the difficulty in initiating or sustaining voluntary activities, and classified into mental and physical fatigue [1]. Exercise-induced fatigue usually associates with increased stress levels caused by modern lifestyles, along with a decline in exercise performance [2]. At present, several theories including \"exhaustion theory\" and \"radical theory\" have been put forward to explain the mechanisms of exercise-induced fatigue [1]. Among them, the \"exhaustion theory\" speculates that energy sources, including glucose and liver glycogen, will be exhausted during exercise, which is accompanied by physical fatigue. In this theory, some studies indicated that post-exercise nutrition through the administration of proteins, saccharides, and amino acids can eliminate the accumulated harmful metabolites, repair the damage of organisms, and facilitate recovery from fatigue [3]. Compared with these nutrient substances, protein hydrolysates and peptides have been widely studied due to their potential health benefits associated with high bioactivities, low molecular weight (MW), easy absorption, and less toxicity [4; 5]. [PERSON] et al. reported that jellyfish collagen hydrolysate could promote climbing endurance and had anti-fatigue effects in rats [2]. [PERSON] et al. reported that the spleen-derived peptide CMS001 had anti-fatigue effects in mice. Therefore, bioactive protein hydrolysates and peptides are believed to be helpful for counteracting and ameliorating physical fatigue [6]. Except for exhaustion of energy sources, high-intensity exercise often destroys the balance between the oxidation system and anti-oxidation system of human body. The accumulated reactive oxygen species (ROS) will put the body in a state of oxidative stress and bring injury to the body by attacking biomacromolecules and cell organs [6; 7]. Some reports found that exogenous dietary antioxidants can decrease the contribution of exercise-induced oxidative stress and improve the animal's physiological condition [5]. [PERSON] et al. reported that load peptide could scavenge hydroxyl radical (HO\(\bullet\)) and, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH\(\bullet\)) in vitro and increase the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in vivo [1]. [PERSON] et al. reported that high Fischer ratio oligopeptides derived from food sources such as corn, tuna, and _pinctada martensui_, could scavenge free radicals in vitro and increase the activities of SOD, CAT, and GSH-Px in vivo [8]. In addition, high Fischer ratio oligopeptides could prolong the swimming time, increase liver glucagon contents, and lower blood urea nitrogen (BUN) and lactic acid (LA) levels of exercised mice. However, the anti-fatigue and anti-oxidation mechanisms of protein hydrolysates and peptides have not been fully elucidated. Therefore, more detailed research should be done seeking more high-efficiency antioxidant peptides used in the daily diet to reduce oxidative damage and fight against fatigue. At present, large quantities of byproducts, accounting for 50%-70% of the original raw material, are generated during the aquatic products processing, and optimal use of these byproducts are an effective approach to protect the environment and produce value-added products to increase the revenue of fish processors [9]. Therefore, preparation of protein hydrolysates and peptides from fish byproducts are extensively researched [5; 10]. Proteins in food resources possess a variety of active peptide sequences, and enzymatic hydrolysis is thought as an effective method to release those active fragments without destroying their nutritional value and adding hazardous substances, including residual organic solvents and toxic chemicals in the final products [4; 5].