Sleep has been directly linked to muscle growth. Extensive research has shown a lack of sleep hinders the muscle building process. The reduction in sleep reduces your bodies ability repair muscle tissue, significantly reducing the effectiveness of muscle protein synthesis. Not getting enough sleep can impede the recovery process, leading to declines in muscle growth & potentially leading to muscle loss.

Sleep is the bodies primary recovery phase, & is indeed needed in order for your body to properly undergo muscle development.

Growth Hormone Release: Deep sleep (especially slow-wave sleep) help trigger the release of growth hormone, which is an obvious essential need for muscle repair, recovery, and growth.

Protein Synthesis: Sleep enhances muscle protein synthesis, allowing damaged muscle fibers to rebuild stronger after exercise. In order for the cells to build new proteins, sleep is essential. Protein synthesis is needed for muscle growth, repair, and overall body function. In the context of fitness and muscle building, it refers to the creation of new muscle proteins to repair and strengthen muscle fibers after exercise.

Testosterone Production: Quality sleep maintains testosterone levels, a key hormone for muscle growth, strength, and recovery.

Cortisol Regulation: Sleep deprivation increases cortisol, a stress hormone that promotes muscle breakdown (catabolism) and impairs recovery.

Energy Restoration: Sleep replenishes glycogen stores, the bodies primary energy source, ensuring better performance and endurance.

Reduced Inflammation & Injury Prevention: Proper sleep minimizes inflammation, helping prevent overtraining and reducing injury risk.

Cognitive function: A lack of sleep can cause a crash in decision making, refined focus, & impaired learning abilities. 

Mood: Irritability & mental fatigue arise after poor sleep. This will make it much harder to make it through workouts/training efficiently. 

Research articles supporting this information:

Research indicates that sleep deprivation can impair muscle recovery by increasing protein breakdown, adversely affecting protein synthesis, and promoting muscle atrophy. ciss-journal.org

The findings in this study suggest that maintaining good sleep quality is essential for muscle preservation and overall body composition. bmcpublichealth.biomedcentral.com

A comprehensive review on sleep and athletic performance concluded that increasing sleep duration, either at night or through napping, effectively enhances both physical and cognitive performance in athletes. sportsmedicine-open.springeropen.com

Another review emphasized sleep's fundamental role in physiological growth, neuromuscular performance, cognitive functioning, memory consolidation, emotional well-being, and immune function, all of which are vital for athletic performance and recovery. researchgate.net

study involving nearly 70,000 middle-aged women found that those who slept 5 hours or less per night were 32% more likely to experience significant weight gain and 15% more likely to become obese over 16 years compared to those sleeping 7 hours. verywellhealth.com