The scientists looked at the proteins in sperm from healthy men and those with low sperm motility to understand why some men struggle with fertility. They found that in men with low sperm motility, issues like problems with how the sperm use energy or defects in tail proteins can lead to reduced movement. Some specific proteins like COX6B, ODF, and TUBB2B were highlighted as playing a role in sperm motility. By comparing the proteins in sperm from healthy men and those with low motility, they identified potential reasons for reduced sperm movement and possible markers that could help in diagnosing fertility issues.