This time of year, it is not a bad idea to be in a strength endurance phase for cyclists. Think of 3-5 minute big gear slow grind hill repeats to get an idea of what your gym workouts should look like.
For convenient big bang for your buck movements, dumbbells and kettlebells held in the Dan John "Goblet" position can provide a lot of work in a short amount of time. Pick the right exercises and you can move every muscle in the body at once, drive your heart rate through the roof and develop strength off the bike to make being on it that much better.
The following exercises are three lunges variations that I feel are critical to keep the hips happy, build strength as well as increase mobility. Not too mention hammering the core at the right loads. Add this all up and you just might get that KOM you lost on everyone's favorite cycling website.
The goblet position also activates the lower abdominal wall quite a bit when you come back to the standing position when you use it. Working the abdominal wall and the glutes in one exercise is a pretty efficient way to build strength.
To get the January grind effect, you can combine a push and a pull with each lunge variation. For instance, it could look like this with 5 reps of each exercise (10 total on the lunge variation chosen) and 2:00 to 3:00 of moving and 1:00 to 2:00 minutes of rest x two to three sets to simulate a total body strength building hill repeat grind.
You should be working at a 6.5-7.5/10 in terms of intensity so you can survive each round. Rest as needed, DON'T move just because the clock is running. Quality is much better than quantity. With consistency, latter will catch up with the former.
1) Lunge variation
2) Suspension trainer (monkii bars, TRX, rings, etc) pull
3) Bodyweight pushups
Exercise bands make a good addition to this sequence as well and go a long way to getting the heart rate to go through the roof as you work.
1) Lunge variation
2) Hinge plus pull
3) Squat and press
1) Kettlebell Goblet Lunges
This a great exercise for quite a few reasons. You'll activate the core quite a bit on top of the muscles of the low back that you need to grind out a climb and keep a long descent under control at speed.
The lunge portion can also loosen up the hips, stretch the quads (which are typically tight and very often over active on cyclists) as well as work on the necessary components of single leg stability and strength of riding a bike better.
2) Kettlebell Lateral Lunges
Take all of the benefits of the above lunge and add opening the hips up through lengethening the adductors. Which is a very good thing. Especially if your knee goes in toward the top tube as you ride. This movement also takes the body left and right to undo the uniplanar action of cycling and sitting at a desk all day.
3) Dumbbell Goblet Cross Over Lunges
Take the benefits of the lateral lunge, and insert opening op the outer hips with the cross over (or curtsy) lunge. I LOVE this movement. The bodyweight version of this is something that should be done post ride, heck, every day that ends in the letter "Y" for that matter. This move works to both strength and mobilize the hips, and that's a good thing. You can also use a kettlebell as well for these.