Yes, getting a HR monitor will be useful. During base period, almost all of your swim, bike, and run workouts should be done at a VERY low intensity.

Ken

I am not a coach but this is my understanding-

The base training that people are doing on their bike/running/pool so forth is a ‘respiratory’ workout. If you go above your aerobic threshold heart rate during these types of workouts for long periods of time you will affect your base building. For example, my AT is 154 beats/min on the bike. I try to stay at or under my AT as much as possible during my rides in the off season. However, I will still go for a hard ride or spin once every 10 days or so but I don’t count it towards my base building time. I don’t know the recommend percentage of how much time your need to stay below AT during base building but I don’t think 30 mins over AT twice a week would hinder any foundation building.

Lifting, push-ups, and pull-ups are ‘muscularly’ workouts not ‘respiratory’ and you will definitely benefit from doing these types of workouts in the off season.

buying a heart rate monitor, and getting on a program based on heart rate will be the best money you could spend on equipment. Take a look at Joel Friel cyclist's bible or Chris Carmichael's books on training to learn how to figure your appropriate HR for different workouts.

what is the negative consequence of going above the intensity level while base training?

Here is something you all should look at and read. AeT training in Zone 1 (Friel) is not the best. Read it. It's good. We must push the aerobic threshold to anerobic but STAY aerobic.

Firel says:

The optimal way to train any physiological system is to create and frequently repeat a stress that precisely targets the system. When it comes to the aerobic system that target is the aerobic threshold (AeT). When training at the aerobic threshold, all of the key aerobic systems are stressed and the stress can be maintained for relatively long periods of time just as one must be able to do in an endurance race.

http://active.com/story.cfm?story_id=12685&sidebar=26&category=triathlon

Cardiac drift at a certain HR for a duration of time I find, during running, is one of the best ways to tell over time if you're making any progress over a set distance apart from track tests.

Friel identifies it and says this:

Essentially, when an athlete is in good aerobic condition his or her heart rate and power or pace will stay closely coupled at aerobic efforts....... If power or pace drops off relative to heart rate, or if heart rate rises relative to steady power.........or pace the athlete is said to be aerobically decoupling. If this is greater than one percent shift, then more aerobic training is necessary.

For long distances what we want is to increase our lactate threshold (LT) so that we can go at a higher HR longer (i.e., for 1/2IMs and IMs) staying aerobic, but at a higher HR. The best way to do this is with time intervals using the above Friel article info in that work to increase LT is best when we spend interval time (lengths of higher HR sessions) right near the LT but still staying aerobic (http://www.pezcyclingnews.com/?pg=fullstory&id=1040) i.e., just sub LT.

I know, once I saw that I said, why the he** can't somebody simplify things so well elsewhere. Always WAY too much extra stuff added in. This really makes things sweet and to the point.

From what I understand going LT once per week is good, even in base to improve the LT threshold. Like other times of the year this can be a benefit. But, the way I get it is that you should be training 95% of the time just below the LT to get the max. out of the lactate curve shown in (http://www.pezcyclingnews.com/?pg=fullstory&id=1040) (Fig. 2), if you can figure out your LT for sure to lengthen that LT line (in blue) before it goes red. The HRmax and the 80-85% rule is a pretty good indicator of most peoples LT threshold. I find that I get a stronger burn in the quads at that % (80-85%) and know I am either at or close to the LT. For e.g., if your HRmax on the bike is say 185bpm then I guess we should be below 157bpm (85%) to stay at the top of the aerobic scale; when riding to get the max. benefit we should also be riding as close to this level as long as possible if we can maintain it to get the most from the session. If not then it might be a good idea to do several long sets (intervals) to this level as well during the base period and say only once a week for a short duration go above it to say 160+bpm kinda thing. The way I get it is that frequency for workouts (more the better) and consistencey for these higher aerobic spikes is critical to get the most benefit during base, or any other time for that matter; workouts should be done regulary is my understanding. Correct me anyone if I am wrong in my interpretation pls.

I'll definitely try and keep a log of it.