Purpose: This study examined the relationship between muscle cross-sectional area (CSA) with strength and power, as well as its changes following resistance training. Results indicate that CSA increase may be a predictor of strength improvement, though this relationship depends on individual factors, training status, and program type. Methods: The research consisted of two parts. In study one, 40 participants (trained and untrained) were evaluated. In study two, 20 participants were assessed before and after a hypertrophy-oriented resistance training program. Quadriceps CSA was measured using Tesla MRI, 24 h before (both studies) and 48 h after training (training group). Pearson correlation and regression analyses were performed in SPSS v26 (P<0.05). Results: In study one, CSA was positively correlated with strength (r=0.57) and lower-limb power (r=0.44). Strength and power were also correlated (r=0.41). In study two, CSA changes in the right leg correlated with strength (r=0.49) and power (r=0.39), while the strength-power correlation was low (r=0.38). In the left leg, CSA changes correlated with strength (r=0.52) and power (r=0.47), with moderate strength-power correlation (r=0.51). Conclusion: CSA is significantly associated with strength, but its relationship with power is weaker. High-volume resistance training increases CSA and improves strength and, to a lesser extent, power. The impact of CSA changes on power appears limited, suggesting that the type of hypertrophy training plays an important role and requires further investigation.