Amino acids and proteases are pivotal for post-exercise recovery, playing crucial roles in muscle repair and protein synthesis. They aid in rebuilding and repairing muscles subjected to stress and damage during exercise. Branched-chain amino acids (BCAAs) like leucine, isoleucine, and valine are particularly noteworthy for their ability to reduce muscle damage markers and soreness following intense workouts. Proteases, enzymes that break down proteins, contribute to clearing damaged proteins and cellular debris from muscles, making way for new protein synthesis. This tandem of amino acids and proteases helps maintain the balance between breakdown and synthesis, facilitating effective muscle recovery. To harness this potential, it's essential to maintain proper nutrition, including adequate protein and essential amino acids.

Watermelon juice (WJ) offers a blend of beneficial compounds, including l-citrulline, lycopene, glutathione, and vitamins A and C, making it a potential asset for post-exercise recovery. Of particular interest is l-citrulline, which aids in combating fatigue-associated ammonia. Unlike powdered citrulline malate, natural l-citrulline in WJ may have a more pronounced effect. WJ also boasts antioxidants and anti-inflammatory properties due to lycopene, glutathione, and vitamins. However, studies directly addressing WJ's impact on post-exercise recovery are limited and yield mixed results. While some studies indicate improved muscle recovery and reduced soreness, others do not report significant changes. Determining the optimal dosage and addressing potential digestive discomfort requires further investigation.

Taurine, a sulfur-containing amino acid abundant in skeletal muscle, exhibits potent antioxidant properties and has been linked to cytoprotective effects in various tissues. Studies in both rats and humans suggest that taurine intake can reduce post-exercise oxidative stress markers. Additionally, human studies have shown improvements in muscle soreness and force recovery with taurine supplementation, especially when taken for several weeks before exercise. However, there is limited evidence regarding its impact on inflammation. The varying taurine supplementation protocols in terms of duration and dosage warrant further research to determine the most effective regimen for optimizing post-exercise recovery.

Bromelain, an enzyme derived from pineapples and part of the protease family, has shown mixed results in studies investigating its impact on post-exercise recovery. In trained cyclists, bromelain supplementation reduced perceived fatigue and potentially supported testosterone levels during a race. However, it did not significantly affect blood markers of fatigue. Conversely, untrained individuals did not experience enhanced recovery with bromelain after intense elbow exercise.

Notably, combining bromelain with other proteases appears to amplify its effects. Multi-day protease supplements containing bromelain improved muscle recovery, reduced soreness, and decreased markers of inflammation and fatigue. The exact mechanism behind this enhancement remains unclear. However, it seems that bromelain is more effective when consumed in smaller doses alongside other proteases. It's crucial to note that taking bromelain separately from food is essential for it to exert its anti-inflammatory effects.

In conclusion, amino acids and proteases play integral roles in post-exercise recovery, supporting muscle repair and overall recuperation. While these components show promise in enhancing recovery, further research is needed to fine-tune their supplementation protocols and fully understand their mechanisms of action. Nonetheless, optimizing nutrition, including adequate protein and essential amino acids, remains a cornerstone of effective post-exercise recovery.

Credits:

• Chappell, A.J.; Allwood, D.M.; Johns, R.; Brown, S.; Sultana, K.; Anand, A.; Simper, T. Citrulline malate supplementation does not improve German Volume Training performance or reduce muscle soreness in moderately trained males and females. J. Int. Soc. Sports Nutr. 2018, 15, 42.  

• Cunniffe, B.; Papageorgiou, M.; O’Brien, B.; Davies, N.A.; Grimble, G.K.; Cardinale, M. Acute citrulline-malate supplementation and high-intensity cycling performance. J. Strength Cond. Res. 2016, 30, 2638–2647.  

• Da Silva, D.K.; Jacinto, J.L.; De Andrade, W.B.; Roveratti, M.C.; Estoche, J.M.; Balvedi, M.C.; De Oliveira, D.B.; Da Silva, R.A.; Aguiar, A.F. Citrulline malate does not improve muscle recovery after resistance exercise in untrained young adult men. Nutrients 2017, 9, 1132.

• Blohm, K.; Beidler, J.; Rosen, P.; Kressler, J.; Hong, M.Y. Effect of acute watermelon juice supplementation on post-submaximal exercise heart rate recovery, blood lactate, blood pressure, blood glucose and muscle soreness in healthy non-athletic men and women. Int. J. Food Sci. Nutr. 2020, 71, 482–489.  

• Shanely, R.A.; Nieman, D.C.; Perkins-Veazie, P.; Henson, D.A.; Meaney, M.P.; Knab, A.M.; Cialdell-Kam, L. Comparison of watermelon and carbohydrate beverage on exercise-induced alterations in systemic inflammation, immune dysfunction, and plasma antioxidant capacity. Nutrients 2016, 8, 518.

• Martinez-Sanchez, A.; Alacid, F.; Rubio-Arias, J.A.; Fernandez-Lobato, B.; Ramos-Campo, D.J.; Aguayo, E. Consumption of watermelon juice enriched in L-citrulline and pomegranate ellagitannins enhanced metabolism during physical exercise. J. Agric. Food Chem. 2017, 65, 4395–4404.

• Tarazona-Díaz, M.P.; Alacid, F.; Carrasco, M.; Martínez, I.; Aguayo, E. Watermelon juice: Potential functional drink for sore muscle relief in athletes. J. Agric. Food Chem. 2013, 61, 7522–7528.  

• Bailey, S.J.; Blackwell, J.R.; Williams, E.; Vanhatalo, A.; Wylie, L.J.; Winyard, P.G.; Jones, A.M. Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans. Nitric Oxide 2016, 59, 10–20.  

• Camerino, D.C.; Tricarico, D.; Pierno, S.; Desaphy, J.-F.; Liantonio, A.; Pusch, M.; Burdi, R.; Camerino, C.; Fraysse, B.; De Luca, A. Taurine and skeletal muscle disorders. Neurochem. Res. 2004, 29, 135–142.  

• Heller-Stilb, B.; van Roeyen, C.; Rascher, K.; Hartwig, H.-G.; Huth, A.; Seeliger, M.W.; Warskulat, U.; Häussinger, D. Disruption of the taurine transporter gene (taut) leads to retinal degeneration in mice. Faseb J. 2002, 16, 1–18.

• Ito, T.; Kimura, Y.; Uozumi, Y.; Takai, M.; Muraoka, S.; Matsuda, T.; Ueki, K.; Yoshiyama, M.; Ikawa, M.; Okabe, M. Taurine depletion caused by knocking out the taurine transporter gene leads to cardiomyopathy with cardiac atrophy. J. Mol. Cell. Cardiol. 2008, 44, 927–937.  

• Miyazaki, T.; Bouscarel, B.; Ikegami, T.; Honda, A.; Matsuzaki, Y. The protective effect of taurine against hepatic damage in a model of liver disease and hepatic stellate cells. In Taurine 7; Springer: Berlin/Heidelberg, Germany, 2009; pp. 293–303. 

• De Luca, A.; Pierno, S.; Camerino, D.C. Taurine: The appeal of a safe amino acid for skeletal muscle disorders. J. Transl. Med. 2015, 13, 243.

• Ito, T.; Yoshikawa, N.; Inui, T.; Miyazaki, N.; Schaffer, S.W.; Azuma, J. Tissue depletion of taurine accelerates skeletal muscle senescence and leads to early death in mice. PLoS ONE 2014, 9, e107409.

• Silva, L.A.; Silveira, P.C.; Ronsani, M.M.; Souza, P.S.; Scheffer, D.; Vieira, L.C.; Benetti, M.; De Souza, C.T.; Pinho, R.A. Taurine supplementation decreases oxidative stress in skeletal muscle after eccentric exercise. Cell Biochem. Funct. 2011, 29, 43–49.

• De Carvalho, F.G.; Galan, B.S.; Santos, P.C.; Pritchett, K.; Pfrimer, K.; Ferriolli, E.; Papoti, M.; Marchini, J.S.; de Freitas, E.C. Taurine: A potential ergogenic aid for preventing muscle damage and protein catabolism and decreasing oxidative stress produced by endurance exercise. Front. Physiol. 2017, 8, 710.  

• Ra, S.-G.; Akazawa, N.; Choi, Y.; Matsubara, T.; Oikawa, S.; Kumagai, H.; Tanahashi, K.; Ohmori, H.; Maeda, S. Taurine supplemen. In Taurine 9; Springer: Berlin/Heidelberg, Germany, 2015; pp. 765–772. 

• da Silva, L.A.; Tromm, C.B.; Bom, K.F.; Mariano, I.; Pozzi, B.; da Rosa, G.L.; Tuon, T.; da Luz, G.; Vuolo, F.; Petronilho, F. Effects of taurine supplementation following eccentric exercise in young adults. Appl. Physiol. Nutr. Metab. 2014, 39, 101–104.

• McLeay, Y.; Stannard, S.; Barnes, M. The effect of taurine on the recovery from eccentric exercise-induced muscle damage in males. Antioxidants 2017, 6, 79.

• Shirvani, H.; Nikbakht, H.; Ebrahim Kh, G. The effects of soccer specific exercise and Taurine supplementation on serum cytokine response in male elite soccer players. Ann. Biol. Res. 2012, 3, 4420–4426. 

• Buford, T.W.; Cooke, M.B.; Redd, L.L.; Hudson, G.M.; Shelmadine, B.D.; Willoughby, D.S. Protease supplementation improves muscle function after eccentric exercise. Med. Sci. Sports Exerc. 2009, 41, 1908–1914.

• Shing, C.M.; Chong, S.; Driller, M.W.; Fell, J.W. Acute protease supplementation effects on muscle damage and recovery across consecutive days of cycle racing. Eur. J. Sport Sci. 2016, 16, 206–212.  

• Stone, M.B.; Merrick, M.A.; Ingersoll, C.D.; Edwards, J.E. Preliminary comparison of bromelain and ibuprofen for delayed onset muscle soreness management. Clin. J. Sport Med. 2002, 12, 373–378.

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