Several positions for prayer are mentioned in the Bible, standing, kneeling, lying down, prostrate. No significance is given to the position of the body, it's the position of the soul that matters.
Romans 12:12 (NASB)
12 rejoicing in hope, persevering in tribulation, devoted to prayer,
18 With all prayer and petition pray at all times in the Spirit, and with this in view, be on the alert with all perseverance and petition for all the saints,
Phil 4:6 – 7(NASB)
6 Be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God.
7 And the peace of God, which surpasses all comprehension, will guard your hearts and your minds in Christ Jesus.
1 Thess 5:16 – 18(NASB)
16 Rejoice always;
17 pray without ceasing;
18 in everything give thanks; for this is God's will for you in Christ Jesus.