Hi Missy,
my dog Nelson has just turned two and he is going for his Endurance Title at the end of the month. This a 20 km (approx 13 miles) steady "gaiting" done at an average of 10 km per hour in 3 stages. 8 km, 15 minute rest, 6 km, 20 minute rest and a final 6 km. The dog must be checked by a vet 2 weeks prior to the run and is checked during the test and after and with some basic obedience to make sure he is still "with it". The test is over a variety of surfaces - concrete, tarmac and grass. It is important to get your dogs pads conditioned for such a long event.
I started taking Nelson on short runs 3 to 4 kms (2 - 3 miles) when he was 18 months old and have now built up to 14 kms (9 miles) in a single run. The minumum we do now is 8 km (5 miles) and regardless of the distance we aim for an average pace of 11 km per hour, not Olympic stuff, but hey I'm getting on
The important point is to build up endurance and finish a long run strongly, not puffed out.
When you do start doing longer distances you may find it easier just to take the one dog. Rhythm and pace are all important and is much more difficult to maintain with one dog let alone two.
Sometimes I'll run Nelson 8 kms and then take 8 year old Natasha out on a 3 km run if my wife is unable to exercise her. I can run them both together, but they tend to "compete" for the lead and I have to continually check them to get them next to me in a reasonable heel position.
We train for about 3 runs a week clocking up 20 to 30 kms total with mixed distances between 8 and 14 kms. Frequency is important as are rest days. Anything over 10 kms needs 2 full rest days and consecutive runs need 3 rest days. I figure if my muscles are sore so are his.
Boxers are naturals at distance running with long strong legs and huge chest cavity for a large aerobic capacity. What can be hard to do is to get them to realise that when you start out it's not a sprint up the street! Nelson usually settles down next to me after about 4 or 5 kms. He, like most Boxers likes to "lead" the way even when running!
Since starting the longer runs Nelson's appetite has gone way up too and his body condition is just fantastic. We show him and his physical condition makes many of the other entries look "flat" and unconditioned.
If you do train your dog as much as I am doing with Nelson at the moment, make sure he gets extra food in the morning, a lunch time snack and extra in his dinner. Regularly spaced meals are the best for absorption of proteins and other nutrients. Give him a vitamin and mineral supplement too.
Also don't run your dog for at least 2 hours after he has had a meal and don't feed him for at least 1 hour after a run. Boxers can be prone to "bloat" a life threatening condition. Feed him instead a split meal after the hour. Half first, wait 15 or 20 minutes and then the other half. A long run makes them **very** hungry and they just want to gulp the food down - not a good thing so you have to get them to eat a bit slower, hand feed or let them eat a bit, pick up the bowl, wait 15 - 20 seconds put it down again, and so on. Sometimes it's a real trial but safety first.
Watch the weather conditions too. A boxer will run with you whatever the weather, but temperatures over 25 C (77 F) start to get too uncomfortable for them. I won't run if it is 25+. I find Nelson much prefers (as I do) early evening/morning runs when it is quite cool (13 - 17 C, 55 - 62 F). Running in direct sun even when it is cool can be taxing too as Boxers are generally dark and they heat up easily in the sun.
A good idea is to also do some physio on you dog. Gently massage his legs and back and chest and if you know of a good pet chiropractor take him once in a while to have his spine and limbs adjusted.
Swimming is also an excellent exercise as an adjunct to the running in building up endurance, power and helps exercise other muscles not generally used in running. Nelson goes to the "K9 Swim n Gym" every few weeks and will spend about 40 to 60 minutes doing "laps" of the indoor dog pool. He just loves it!
A final thing. If your dog feels he needs to be rewarded for helping you get fit by keeping you company on your runs and wants to sleep on your bed with you after a long run, then really you should let him. It's the least one can do
Best of luck training Magnus. If you have any questions please ask.
While we do not run these distances with our dogs all the time, Bella has her Endurance title (20km run). She was 5 at the time she gained this title. As our main focus is agility all our exercise with the Boxers is designed so they (the Boxers), are very fast and powerfull over short distances. It was a bit of a challange to get Bella ready for long distance work as we had to change her from a 100m runner into a marathon runner