4:35 1600m ~ 4:15-17 1500m in my opinion.
First thing I would do is try to recognize what elements of your training helped you to improve. Maybe it was just more consistent, unbroken and healthy training, or maybe it was more specific things like focusing on core strength, lactate threshold runs, long runs, mileage, certain kinds of workouts, etc., etc.
Basically you're looking to improve by running each 400m 4 seconds faster, which is running each 100m seconds 1 second faster for 1500-1600m.
Since you just finished cross training, with more specific training for the 1500-1600m, I would think that you could improve upon your 4:35 by about 6-10 seconds, but only after 2-3 months of training aimed at that goal. So, LET'S SAY you're capable of running 4:25-4:29 in the spring for 1600m- that puts you at about 4:05-4:07 for the 1500m, and this is still your junior year.
I think it's deffinately within reason that you can run 4:00 by the end of your senior year, but 3:45 could be pushing it. Improving is similar to the function squareroot(t) if t represents time and it's assumed that you're constantly improving. It will deffinately get harder once you start training in the 3:50-4:00 1500m range.
My suggestions(what do i know - you may not want to keep reading if you've made it this far):
I'm not sure what kinds of routines you have in your training regime, but make sure you do a set of strides for 80-120m 2-3 times a week, even during the base training phase. You always want to make sure that you are developing strength in ALL areas of your bodies - even muscles you think you never have to use or are probably unaware of.
Core strengthening is important as well. Developing a stronger core will make you a more efficient runner, and will actually make your running workouts more beneficial because less energy/work will be focused on correcting imbalances in your form.
Develope that speed. It seems like you deffinately have potential if you've made it this far from 5:07 without any serious drawbacks, which most likely would've prevented you from making it this far. Make it a goal to get your 800m PR down in the 1:54-1:56 range. That's a whole 6-8 seconds from your current PR, but how much time to you spend on increasing the number of quick-twitch fibers in your muscles?
Short hill sprinting repeats no longer than 100m with full recovery can help. These aren't meant to develope your AnT system, but to improve your neurosystem, as in how well your muscles are able to fire off from the signal your brain sends to them, and also to develop specific strength for your particular body. Make sure you don't do this workout too often(once every 2-3 weeks) because it can be stressful on the body, and watch the downhill jaunt- that can be stressful on the joints as well.
As you do higher-caliber workouts, you may want to alot more recovery time between them. These could be days where you go 'easy' but still maintain a certain minimum pace(maybe 6:15-6:45 min/mile in your case), and these could be good days to do strides to keep the leg muscles loose and whatnot.
And always approach new types of workouts/training with caution. Don't over-do anything that is fairly new because if it is really new to the kinds of stresses you've put on your body before, it's going to take time for your body to adapt to these new stresses. Over time, it would be okay to increase them in frequency, and after that, increase in intensity, but make sure you give plenty of time. Patience is an invaluable virtue.
I've probably reiterated enough from everything I've read and heard over the years, and hopefully this will help you. But just try to set small goals. Small enough that if you acheive them, you can feel like you are getting somewhere slowly, but not so big that if you don't acheive them right off the bat, you don't think it's the end of the world because they shouldn't be so big that you shouldn't be able to acheive by the end of whichever season you're in. Good luck.
Here are some workouts that might be good from here until your track season:
Developing base:
Depending on where you are at now, how much you've increased your mileage over the past year and how beneficial it's been, you may or may not want to increase your mileage. Here's a chart for, where you're at and if everything's felt fine, I correlate that with mileage to increase to that I think would be safe building up to over 4-8 weeks and maintaining for 6-10 weeks(all depending on how it's going for you).
mpw now --> mpw in the near future
30 --> 45
35 --> 45
40 --> 50
45 --> 55
50 --> 60
55 --> 65
60 --> 65
65 --> 70
70 --> 75
75 --> 80
80 --> 85
85 --> 90
etc.--> etc.
Base training:
1. 1 tempo run every 7-14 days. You don't want to make these too frequent because you a.) want to give you body's systems time to development before putting this stress on them to develop them further and b.) too many of these too often can fatigue the body. I would do 4-6 (20-35 min.) mile tempo runs in your case, since you're looking to improve in the 800m-1500m range.
2. Long hill repeats and those short fast hill sprint that I talked about earlier. For the long hill repeats, 800m repeats would be plenty long enough in duration, as long as you're doing them at, say, 5-10k race effort(depending on how many you do). 4 x 800m uphill @ 5k effort would be great, or 6 x 800m @ 10k effort. Both with jog down recoveries.
3. Strides. I already talked about this. Do them at least once a week, no more than 3 times a week is necessary. Do something like 6-10 x 80-110m strides 2-3 times a week, ON GRASS. These should feel like you're moving at almost your 1600m pace, but you should also feel relaxed and with enough energy to have nice, bountiful strides.
4. Long runs. Do 8-12 mile long runs, sometimes changing the pace, like maybe increasing the last 3-5 miles of the run, or doing the middle 3-5 miles at a cruise interval(less intense than tempo) pace.
5. Strength. Core exercises likes situps/crunches, pushups, planks, side-planks, 'the bridge'(look it up), yoga is good(Shalane Flanagan did this often), and using weights isn't really necessary for this, although for someone looking to improve 800m-1500m strength, it probably would be a good idea. But stick to the ligher weights(15-30 lbs. with more reps). Swimming and bicycling is good too, as the cross training will help to strengthen other areas of your muscles and different muscle groups in general.
6. Probably one of the most important things in training, in general, is the moderation of your training. Never focus too much on one type of workout. Use a collective amount, as it will exercise different muscles groups, and give other muscle groups time to rest. Don't do lots of slow running, especially on hard surfaces, and don't do too much fast-paced type training. Moderation is key, in general, and in life.
7. Last comment about this phase: Main goals should be improving the cornerstones of what will help you become better in a specific field: aerobic system, lactate threshold system, & raw strength. 'Easy' running between the hard days, workouts that build up lactate at distances no shorter than 1-2 miles, and basic strength.
Transitioning from Base Training to Racing Phase/Specific Training:
1. Aerobic Power: Now you want to start making your body feel more familar and almost more comfortable with running at certain intensities, which consisnt of running at certain aerobic and anaerobic threshold, because you will be looking to improve a bit more from where your base training took you. These will be shorter in lenth(compared to 1600m-3200m repeats) and accordingly a bit higher in intensity. These might look like:
3-6 x 1000m @ 8k race pace w/ 2:45-3:30 min. rest in between.
A more specific workout that might be good for you may look like:
4 x 1000m @ 2:50-2:55 (64 sec/400m pace = 2:40/1000M) w/ 3:00 min. rest, maybe something like:
2:56, 2:54, 2:52, 2:50
or
6 x 800m @ 2:14-2:18 (67-69 sec/400m) w/ 2:00-2:30 rest
2. Faster, Shorter Intervals: These would workouts the help your body get more comfortable with running at faster speed. Mainly helping your muscles to develop to the new stresses of running at faster repetitions with faster leg turnover. This could also be something that start out in the middle to late stages of your base training, slowly introducing it with brief workouts of 4-6 x 200m @ 3k pace every 2-3 weeks. But when this transition phase comes along, you want your body to adapt to running at more intense paces- make sure the machanics of your body are comfortable with being able to train at intervals that will be longer than this without causing too much stress on joints/tendons/etc. These might look like(for you):
8 x 200m @ 31-32 seconds w/ 60-75 seconds recovery or 300m jog.
The point of these intervals IS NOT to build up lactate threshold, but to get your muscles/joints/bones/etc. comfortable with these kinds of stresses, so I wouldn't do more repetitions than this, and 4-6 repetitions at this kind of intensity might be good enough for your body. You will naturally build up a little lactate threshold for running on these intensities, but should not build up much. That is designed for later. Again, the athlete and coach constantly need to evaluate the condition and response to the training on a daily basis.
These short, repetition intervals are meant to help prepare your body for running repetitions of 400m-800m at 64 second/400m pace. This is the pace that would come out to about 4:00 for 1500m.
3. Long runs & Tempo runs should still be consistent in your training at this period. A tempo run that exercises your lactate threshold should still be done every 1-2 weeks, and I personally would keep them at about the same length, maybe just slightly shorter. I would say doing tempo runs at 3-5(15-30 min.) miles would be appropriate for this period in your training. The long runs are also imporant as you want to make sure you are still keeping your aerobic system in shape and balanced because it will continue to help you in the long run(no pun intended) and help to keep a more even pH balance in your blood. When you do more anaerobic type workouts, your pH balance becomes more acidic, i think(?)- i know it just becomes something you don't want to have in your blood if you're hoping to maintain your endurance fitness for a long while after. So the long run will be important from this point unti about the time you start the peaking process.
4. Strength. Core strength and weight training is still important, and will be important until your final peaking workouts. On this subject, however, I do not have a whole lot of information, as far as whether or not to decrease workouts and increase intensity or whether to keep the workouts the same. I do know however that stimulation is the key to improving, so you never want to keep doing the same workout over and over again for long periods of times. For your core strengthening exercises, I would just increase the intensity by the same amount you increase the intensity in your other workouts(because it's all about the progression of anaerobic:aerobic threshold fitness particular to the event/stresses you're training for). So if you were doing 2 x 30 situps/crunches 3 times week in your base training phase, I would start doing 2 x 40-50 situps 2-3 times a week(maybe alternating- 1 week twice, the next three times) and likewise with the other core strengthening workouts. I wouldn't be on the bike or in the pool any more at this point, as these were designed for cross training and improving strength, and now that you would be transitioning into the more specific endurance phase, these would have less importance(unless you wanted to do workouts to optimize your lactate threshold to specific bounds without straining your joints/ligaments/bones as much, like if you were injured or maybe for other reasons). Basic strength to your particular build and body will be important until your cross the finish line of the finals in whatever championship race you hope to be in.
Specific Training Phase: Now we get to the sweet stuff. All the prior months of training your body at different threshold and strengths will be pushed into intense training to get your energy and muscular systems operation at the exact level you want them to. This is the almost the final push:
Repeat 200m-600m workouts, but remembering to keep the aerobic element present:
6-10 x 400m @ 99% goal race pace:
4 x 600m @ 1:40 w/ 1:45-2:00 min. rest
3 x 600m @ 1:36 w/ 1:30-2:30 min. rest
2 x 600m @ 1:32 w/ 2:00-3:00 min. rest
10 x 400m @ 66 seconds w/ 60 seconds rest
8 x 400m @ 65 seconds w/ 60 seconds rest
6 x 400m @ 64 seconds w/ 75-90 seconds rest
12 x 300m @ 52 seconds w/ 60-75 seconds rest
10 x 300m @ 50 seconds w/ 60-75 seconds rest
8 x 300m @ 49 seconds w/ 60-90 seconds rest
6 x 300m @ 48 seconds w/ 45-90 seconds rest
4 x 400m @ 45 seconds w/ 1:30-2:00 min rest
8 x 200m @ 32 sec. w/ 45-60 seconds rest
6 x 200m @ 30 sec. w/ 45-60 seconds rest
4 x 200m @ 29-30 sec. w/ 45-90 seconds rest
2 x 200m @ 27-28 sec. w/ 0:30-2:00 min. rest
First of all, these wide variety in rests depends on what you are trying to train at the time. If you are looking to increase lactate threshold, less time, and maybe not as fast, is what you're looing for. So something like 10-12 x 200m @ 30-32 w/ 45 seconds rest would be good for this. My coach in high school use to have us do a workout called 'Chicago 220's' that Newton has his boys do as well and it went like this:
20 x 200m @ 30-36 sec.(depending on ability):
4 x 200m w/ 60 seconds rest
4 x 200m w/ 45 seconds rest
4 x 200m w/ 30 seconds rest
4 x 200m w/ 15 seconds rest
Donald Sage loved this workout, because, in his own words, 'you really have to sprint', meaning you really have to push hard. This would probably be a good wokrout for you, seeing as how you are probably already within the ability of doing workouts at this range.
But for the other reps where I left the time recovery rather ambiguous, it depends on what you're trying to do. If you're trying to increase lactate threshold, either moderate reps still faster than race pace but with little reovery is good, or if you're looking to imrpove basic speed, more recovery is better. This would be for when you're looking to peak. For my last few workouts, I might do a lactate threshold workout (like 12-16 x 200m @ 30 w/ 30-45 seconds rest) and follow it up 2-4 days later with a 4 x 200m @ 28 seconds w/ 1:30-2:00 rest. The key is you want to feel fresh and not worn out when you get ready for your final racing.
You still want to plot out this last period as a kind of 'zoning in' on that specific pace you're looking to make. Maybe doing a workout like
4-6 x 400m @ 65 w/ 200m jog recovery
would be good, because coupled with some 200m workouts, you would develop the speed to close that gap betwen 65 seconds 400m lap pace and 64 seconds 400m lap pace.
You also want to make sure you are still sticking with your strides(3-4 times a week now) and also giving yourself plenty of time for recovery between workouts. You don't want to be doing more than 3 medium-hard workouts a week or more than 2 hard workouts a week. You want to make sure you balance you anaerobic threshold with your aerobic threshold so that you don't peak too soon, and this can be a tricky thing. The long run every week won't be as necessary, but once in a while(every 2 weeks) is good to maintain your aerobic endurance. Also keep up with the core strengthening, because as you demand more of your body, your core strength will become more imporant, so the intensity will need to be increase a bit as well. The important thing though is to manage the appropriate rest/recovery time between these increasingly intense workouts, which, after a while, will become less intense, because you will be looking to make sure you feel fresh and relaxed for reach upcoming race.
I hope this helps your running. If not, I'm sorry. I just love learning and talking about training. Enjoy the ride.
P.S.
Just one last workout:
3-4 x
(1 x 400m @ 61-62 w/ 1:30-2:00 min. rest
2 x 200m @ 29-30 w/ 1:00-1:30 min. rest)
w/ 3:00 min. rest between sets