什么叫during exercise？

Many muscles of the trunk are involved in breathing, including the diaphragm, intercostal, scalene and abdominal muscles. Many of these muscles have other roles such as maintaining posture and during exercise, so their coordination as respiratory muscles as well is complex.

1.怀疑是doing exercise的误写？理由：and前后应该并列，maintaining无法与during并列

2.有的专家说把它分成两个句子1.Many of these muscles have roles maintaining posture; 2.Many of these muscles have roles during exercise; 

这样一看能用 and 连起来，这样就没问题了，roles such as maintaining posture and roles such as during exercise，roles such as省略了

或者也可以理解为 "roles such as maintaining posture (when staying still) and (maintaining movement) during exercise

3.有的专家说during exercise和前面的内容没关系，调整成这样的顺序就清楚了  "Many of these muscles have other roles such as maintaining posture and so their coordination as respiratory muscles  is complex during exercise as well."  

只是我觉得so是因果关系，so和前面的那句话还有逗号隔开，during exercise能前置吗？

麻烦高手回答？