Studies have shown that a pre workout supplementation can increase aerobic performance, training volume, and lean muscle mass [1]. Bodybuilding.com Signature Pre Workout provides a combination of leucine, taurine, beta-alanine, citrulline, caffeine and electrolytes to help you prepare for your workout.

Here is a brief explanation of the ingredients and its function.

Leucine is arguably the most important branched-chain amino acid (BCAA), because it has shown to greatly increase muscle mass, help with fat loss, and prevent muscular fatigue by stimulating acute protein synthesis [2].

Taurine can help improve your muscular strength by reducing muscle fatigue from  oxidative stress. Taurine plays a beneficial role in your metabolism, glucose regulation, energy levels, anti-inflammatory modulation, and antioxidant actions [3]. 

Citrulline is an amino acid that may help increase nitrogen levels in the body which can increase blood flow to your muscles.  It has also been shown to increase athletic performance in high intensity anaerobic exercises and to relieve post-exercise muscle soreness [4].

Beta Alanine is a precursor to carnosine which can help you delay muscular fatigue during high intensity exercise by acting as an intracellular pH buffer [5].  Studies have shown that beta-alanine can increase lean body mass, number of repetitions performed, and overall training volume [6]. It has also been shown to lower perceived fatigue during high volume workouts [7].  

Caffeine has been proven to boost athletic performance in both aerobic and anaerobic training [8]. Caffeine has shown to increase muscular performance, high-intensity interval training, power output, and cognitive functions as well [9,10,11].

Electrolytes, including sodium, calcium, potassium, chloride, and magnesium, have been proven to help prevent dehydration and muscle cramps during exercise [12]. Maintaining proper hydration and electrolyte balance can help with cardiovascular and thermal strain during aerobic activity [13].

References

1. https://jissn.biomedcentral.com/articles/10.1186/1550-2783-7-10
2. https://academic.oup.com/jn/article/136/2/533S/4664398 
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5933890/ 
4. https://pubmed.ncbi.nlm.nih.gov/20386132/ 
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3374095/ 
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4501114/ 
7. https://pubmed.ncbi.nlm.nih.gov/19083385/ 
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835847/ 
9. https://pubmed.ncbi.nlm.nih.gov/31618910/ 
10. https://pubmed.ncbi.nlm.nih.gov/32024038/ 
11. https://pubmed.ncbi.nlm.nih.gov/32033103/ 
12. https://www.mdpi.com/2076-3417/11/19/9093/htm
13. https://pubmed.ncbi.nlm.nih.gov/22150427/