Training & Nutrition - Maintain muscle mass - 1 long ride or 3 small ones

So ive been told im getting really skinny (im 6'4" so its apparently quite obvious). For the next couple of months im going to cut down on my biking and concentrate on weight lifting a little more. I still want to bike though. I like biking to work but its 60kms in total - would it be better for me to bike to work once a week or do 2-3 shorter rides during the week to keep muscle mass?

Not sure, but how 'bout just increasing your caloric intake?

If you want to keep muscle mass (and apparently build some?):

#1) Eat more than your maintenance. You cannot build muscle in a deficit. There are calculators to determine maintenance but usually people just figure out by eating and when their weight doesn't budge, it's a good sign.

#2) Make sure you are getting enough protein. Figure it out, don't guess: fitday.com

#3) Include weight bearing exercise. You may want to look into size builds vs strength builds. Personally, I would rather be stronger and get somewhat larger, but not as large as a bodybuilder wants to be. This is determined by rep #.
3-6 reps is strength/power
8-12 reps is hypertrophy
12-15 is muscular endurance

Good luck and use proper form.

All endurance cardio is catabolic. You can minimize it with an excess of calories, particularly protein and carbs, but you can't stop it.

However, doing high intensity intervals, even though it's cardio, can both build vo2max as well as muscle mass, provided the intervals are kept short and intense. It's a paradox that hasn't exactly been explained 100 percent, but think about it this way: while both marathon runners and olympic sprinters are physically fit and can process oxygen efficiently, who has the better body? Sprinters have huge upper and lower bodies, while marathon runners look emaciated.

So regardless of the science, rel world proof is in the pudding, as it were.