Is it easier for a full grown adult to get muscles compared to a 14 year old --- EXPLAIN WHY?
Metabolic attributes, such as glycolytic capacity, substrate utilization, and VO2 kinetics also differ markedly between children and adults...
14 year old. Testosterone, puberty and what not.
Both can build muscle at a high rate, depends on training and diet. 14yr old might have a slight age though.
An adult may have more discipline, and knowledge, and resources. But a 14 year old with all that and some dedication could be just as big or even bigger with time. Muscle doesn't come over night. At 14, hormones are going crazy and throughout puberty your body will put on muscle naturally. Pair that with lifting and eating like crazy you have a one way ticket to muscletown.