This is s great article by Lance Watson on incorporating focused training blocks to improve your triathlon limiters...

Triathlon is a complicated sport to train really well at, and we all have areas we need to work on. It’s not just a matter of swimming, biking and running—you have to consider when to focus on skills on the bike, overall strength, swim technique, etc. Athletes’ natural tendencies are to like what they are good at, and therefore they tend to train with a little more intensity or focus in their area of expertise. At some point you will want to improve a single aspect of your game and boost your weakness.

I regularly incorporate single-sport focus or emphasis phases in my athletes’ training to hone an individual event or a specific aspect of that sport. Twelve- to 16-week phases have the most impact on your long-term development, but you can also increase emphasis in one sport for 10 to 14 days and get a “boost” in that sport.

Three-Month Sport Emphasis Phase

For a three-month emphasis, pick a meaningful event to end the phase with, such as a bike race, an open-water swim competition, Masters swim meet or a half-marathon. Try to plan a couple more “building block” events along the way to work toward the goal event, and to keep you excited. You will learn some tricks of the trade from single-sport athletes by participating in individual sport competitions that might not be apparent in triathlon competition.

Keys for long-term development:

– Pick a meaningful goal event for the end of the focus phase.

– Do the first “building block” competition at the end of the three-week phase.

– Move into four to six weeks of threshold emphasis (i.e., short rest intervals, heart rate zones 3 and 4). Still do base once a week. Do one more threshold session per week than you would normally do in your triathlon training for that sport.

– Do one to two more “building block” races in the threshold emphasis phase.

– Move into two to three weeks of speed emphasis (i.e., high speed, long rest intervals, heart rate zones 4 and 5). Reduce base, maintain 60–75 percent of your threshold work, and do one more speed session per week than you would normally do in regular triathlon training.

– Taper for seven to 10 days and then do your goal competition.

Two-Week Boost Phase

For a two-week boost phase, increase frequency, volume or intensity sessions in your area of need. Your training program should be built around the area you are emphasizing, whether it’s your swim, bike or run. You goal is to hit your “boost” sport fresh, and consider the rest of your activities in the other two sports as fitness maintenance rather than fitness building.

Keys to super-charge a single sport:

– Increase frequency in the boost sport by one to two sessions per week.

– Decrease frequency in the non-boost sports by one to two sessions per week.

– Assess more specific areas of need in your boost sport—Is it run threshold? Bike hill climbing strength? Open-water stamina?

– Build your program around the boost sport to ensure you are better prepared for your key sessions. Make sure to have rest days between your higher intensity boost sport sessions.

Other Thoughts to Help You Along the Way

– Seek someone with technical expertise in the focus sport during this phase and put more energy into improving your form and biomechanics.

– Think like an elite single-sport athlete (“I am a distance runner …”).

– Learn everything you can about your focus sport during the phase while you are immersed in it.

– Enjoy meeting new people at different sporting events!

Finally, when you are in race season, stay true to your planned-out, balanced triathlon training plan, but still be in tune with how you are doing in all three individual events.

If you have been struggling in an area for a couple years, incorporate a three-month emphasis phase into your annual plan. If you work with your coach to carefully dissect the individual components of your training, come race day you should be ready to put it all together for a great result.

Read more at http://triathlon.competitor.com/2015/11/training/coachs-note-by-lance-watson-boost-your-weakness-now-and-long-term_125492#BeOx2k77Ew5POe78.99