A half day or even a couple of hours biking can be made into a prayer retreat. I love doing prayer hours on my bike using the Rails to Trails paths near our home. It can be done individually as a personal prayer retreat, or in a group to make it a corporate prayer excursion.
Take plenty of water along, and a little to snack on along the way. I like peanut butter crackers and Slim Jims, or homemade beef jerky. I also always carry along a couple of energy bars such as Power Bars. I always carry some emergency supplies too, like an extra inner tube, and tools to change a tire or tighten something that is loose.
Take along a small New Testament with Psalms or a whole Bible if you have one small enough to carry easily. I take my Mp3 player, which is small, compact and has hundreds of worship selections on it. I also like to take a fanny pack with my CD player (MP3 compatible) to be able to listen to Scriptures and Sermons as part of my prayer disciplines.
Here is how it works. I follow the six Intimacy with God disciplines. Depending on the length of the trek I spend a half hour or an hour on each step. For groups making it a day trip we spend an hour on each with 45 minutes dedicated to the step and 15 minutes of every hour for conversation. I prefer to set up my trip audios sequentially so I don't have to search for music or audios for each step. You can do that by compiling your selected music on your computer and giving each a sequential name so it plays in that order, and then transfer it to your Mp3 player. Otherwise use a CD player and burn a CD in the same way.
A great way to get started is to spend the first hour just riding in silence and observing God's creation around you. Feel the breeze; enjoy the smooth rolling of the wheels of the bike. Reminisce (remember) wonderful childhood experiences riding your bike. Cultivate a consciousness that you are with the Lord. Tell Him so. When I feel quite enough I may turn on some very soft worship orchestrations. I avoid songs with words so as to not be distracted from my attention on the Lord. Sometimes I use nature sounds with background music. It is soothing and fits the ride. It is especially enjoyable if you can arrange this part of the trip to be slightly down hill.
Next, and flowing naturally out of the quiet hour, is time to be thankful to the Lord for all His goodness. I look at nature around me, the birds, squirrels, rabbits, dragonflies, etc. that cross my path. I look at rock outcroppings, deep dark woods, streams we may cross, or in the case of our riverside path, look at the wonders of the river meanderings. You may want to play some thankful music. Quiet music like sounds of nature and orchestrations are also helpful. I like violin music for some of this time. I also love to use Scripture. Psalms of thanksgiving are very helpful to prime the pump of a thankful heart. Speak your thanksgiving aloud to the Lord.
Here is one of my favorite times. I play worship music that is special to me. I am careful to use music I can sing to. Worship is not listening but giving praise honor and glory to the Lord as you ride. Speak praise aloud to the Lord. There are no rules here except that you participate with the music. I find myself at times singing with a loud voice, weeping in worship, and raising or waving my hands in the air to the Lord. Don't be ashamed to be expressive. God loves passionate worshippers.
It is difficult to be introspective while riding a bike, but it is not impossible. I find it is helpful to bring along a sermon you have not heard and let God speak to your heart through that message, then talk to the Lord (and with each other if traveling together) about what spoke to your heart. Spend some time on a break confessing your faults one to another and praying one for another. This is an excellent point in your bike hike to take a long break, eat a lunch or snack and prayer together.
God's word is always a wonderful way to bathe our minds and hearts in the presence of the Lord. I take along some Old Testament passages or a whole book of the Old Testament to help me remember what the Lord has said. The Psalms also contain wonderful promises and prayers that help you put on the whole armor of God. I also use this time to pull out my memory cards or my New Testament and work on committing passages to memory. It is also something you can do together as you ride with a partner. Once you think you have the Scripture committed to memory quote it to you partner and have him/her tell you where you may have missed.
Now it is time to pray about all those things that have been clamoring for your attention all through the ride. I tell the Lord out loud what my main concerns are. Sometimes I have a journal or notes to myself of what to pray about. I pray for my wife, my children, my grandchildren, my parents, my brothers and sisters, my nieces and nephews. One I have exhausted that I pray for the lost people I know, the nation and government, missionaries, our church family and ministries. All the while I will have music playing in the background. I also spend some time singing to the Lord with songs like, "I Cast All My Care Upon You."
Remember this is not a marathon, nor a race. Don't push yourself too hard. Spend a little time to smell the roses along the way. Each person has his own rhythms and pace or speed that is relaxing and comfortable. It has been a long trip; sometimes two hours, sometimes six hours. Don't forget to rest. At the end of the trail sit in the shade beside a stream or in a cool breeze and share with a friend the joy of being with God this day. Have another snack and lots to drink to re-hydrate yourself, then pray for each other.