In this manga about boxing I found the following unrelated sentences:
1) もっと探れ… 伏黒【ふくろ】さんの拳。小さくても攻撃を未然に防ぐため… 芯を通してくる。
2) 芯の通ったパンチを打ってこなくなって… 後退を優先してる。
In the first the protagonist is thinking about how to anticipate his opponent's punches. In the second he is saying that after he stopped blowing 芯の通ったパンチ his opponent preferred to retreat. What is the exact meaning of 芯を通す and 芯の通る? I think they have something to do with determination and strength, but I am not sure. My attempts:
1) I need to understand Fukuro's punches better. They are not powerful, but to anticipate them I need to focus/be determined.
2) After I stopped blowing strong punches, he preferred to retreat.
Here you can see the two pages where the sentences are taken from. Thank you for your help!