This is perhaps the first systematic review and meta-analysis to investigate the effectiveness of WPS over the blood biochemistry mainly amino acids, creatinine kinase and myoglobin which influence performance and recovery among athletes. Then again, the intervention was described as WPS, while others as comparators. The search strategy was robust and unlikely to have missed eligible studies. Of the collected studies, 13 (96%) of the included studies were RCTs which many sources of bias had removed from the process [23]. Two non-RCTs are high quality and the overall assessments had low RoB; this indicated that the two non-RCTs are comparable to RCTs. Meta-analysis is a statistical measurement and procedure for combining data from the multiple studies and developed a statistically single conclusion. The purposes of the meta-analysis are precisely estimate the effect magnitude and identify the reason for the variation and common effect and outcome of data [39].

Whey protein supplements having high levels of serum amino acids of both EAA and BCAA are well known. Furthermore, the results of the meta-analyses illustrated robust evidence that athletes who consumed WPS had higher levels of serum amino acids than comparators. Essential amino acids of WPS were believed to retain and growth of muscle, while BCAA of WPS was believed to delay the onset of fatigue during prolonged endurance exercise [40,41,42]. Moreover, Areta et al. [24] investigated that amino acids of WPS support muscle protein while Impey et al. [29] examined WPS enhanced post-exercise muscle protein synthesis rates. Tang et al. [37] also investigated that a small dose of WP (10 g) was able to stimulate muscle protein synthesis athletes after exercise. Therefore, serum amino acid from WPS absolute ergogenic benefits athletes on delay and recovery from the sports injuries and fatigue [40, 43].

In addition, the myoglobin and creatinine kinase levels were lower in the intervention group which indicates that the consumption of WPS can reduce the muscle fatigue or muscle damage than the comparator groups. The release and elevation in myoglobin indicates the presence of muscle damage or inflammation after exercise [4]. Thus, myoglobin acts as a blood marker for muscle damage [44]. Moreover, kidneys can be impaired when extreme levels of myoglobin are released, known as rhabdomyolysis [45]. Subsequently, a lower level of myoglobin would diminish muscle fatigue to prevent muscle damage while athletes drive their strength [4]. According to the meta-analysis, the overall myoglobin level in the intervention group was lower than that in the control group. Surprisingly, studies have shown that consuming WPS seems to have ergogenic aids as it does lower the myoglobin level [26, 35]. Subsequently, a lower level of myoglobin was reflected in athletes’ physical effort: they could go beyond their maximum physical strength while preventing any severe muscle damage [44].

Creatinine kinase appearing in the blood is considered as a marker of indirect muscle damage [5]. The level is used to assist in detecting athletes’ body condition of tissue damage. It is reasonable for the creatinine kinase level to elevate temporarily due to strenuous exercise [25, 28], but the level should not rise to an extent that could damage skeletal muscles, heart or brain [46]. Therefore, it is essential for athletes to have a lower creatinine kinase level while driving their physical strength. Based on studies, consuming of WPS does lower creatinine kinase level for active athletes [31, 33]. Moreover, Kraemer et al. [30] observed that the WPS delay muscle soreness and improve the intensity of the physical performance. Lollo et al. [33] also studied that the positive effect of WPS on attenuated creatine kinase level could be because the properties of WPS have antioxidant capacity. Hence, lower creatine kinase when consuming WPS will aid athletes to prolong time to fatigue and better maintain or improve exercise performance.

Based on evidence and analyses, WPS is found to be effective in improving the serum levels of BCAA and EAA, and on other hand, WPS has shown a substantial effect on reducing myoglobin and creatinine kinase levels that are markers of preventing sports injuries, These result support the consumption of WPS for the athletes during the routine training and muscle injuries to augment the muscle performance and recovery process.

Limitation

However, there are two main concerns that researchers would like to highlight before any athlete and multidisciplinary team who manages athletes’ health and performance should opt to use WPS; the first one is the higher level of heterogeneity across the compared studies. The subgroup analysis was performed which has shown some declined in heterogeneity for some specific groups. However, for some groups, higher heterogeneity was still there, which is one of the genuine concerns for the researchers while interpreting the results of this meta-analysis. Moreover, the difference in WPS formulation also might have affected the bioavailability and outcome among the studies, and this clinical aspect might have contributed to the heterogeneity in the current meta-analysis.

Recommendation

Future directions for research and conducting research include larger sample sizes, the inclusion of both genders (especially on female athletes), ages, geographical, type of sport and categories of athletes. Interventions that are consumed before, during and/or after sports performances and recovery process also deserve further study, considering the effectiveness of improving athletes’ sports performances and recovery. Additionally, follow-up studies could establish effectiveness for the relation between interventions and long-term performance recovery progress for athletes.

Nonetheless, although WP is recognised as safe supplements for athletes [47, 48], concern arises from WADA insight whereby illegal substances can be found in the interventions from the included studies. Two studies reported an intervention containing caffeine [26, 29] and a study had an intervention containing alcohol [36].

The WADA guidelines and recommendations are updated annually and serve as a guide for consuming supplements during the supports and recovery process for athletes. Therefore, it is highly recommended for athletes, and the multidisciplinary team are well-informed and updated themselves on the guidelines and recommendations before using WPS or any supplements.