at what point do you know to stop training?
 

often when i'm doing something specific (such as hill repeats, intervals, etc.) i have a certain number of repetitions in mind and i usually try to complete them all. naturally i start to get tired and slower toward the end. sometimes i get a little nauseous or light headed but i feel compelled to keep on.

however, is doing too much ultimately hurting my performance? for example, am i gaining anything by struggling up the hill at 25% reduced speed for the two reps? or am i just wearing my body down needlessly?

i know that more training isn't necessarily good training. but how do you know exactly when to call it a day and head home?

As a runner, who in the past did interval sessions as part of road race training, if I couldn't hit and hold target pace during the work interval or I couldn't complete the work interval at target pace or if my heart rate did not recover in the recovery interval to a certain level before the next work interval, then it was time to pack it in for the day.

+1

Also after about 15min total work interval time you are not really gaining much benefit. Mix up doing stuff like: 3x5min, 5x3min or 15x1min. The last sets will always be harder than the first but you should still be getting close to your goal pace.

Yeah, you'll get the most benefit from the first intervals.

I've heard one rule of thumb is to stop when you feel like you can complete just one more interval. (I'd assume that's one more at the optimal speed.)

If you are nauseous you are probably pushing too hard.

Well, usually there's a difference between feeling tired and feeling sick. As far as "knowing" how much to do, a training plan is supposed provide a "system" for determining workout length and intensity, not your "feelings" during the workout.

yeah, i have two habits which i frequently do:

1. i always try to reach my target. for example, if i'm doing 10 hill repeats i'll finish all 10 of them. i seem to be a bit of a slave to my own training schedule even if i'm not "feeling it" that day.

2. if i do feel a little queazy, i sometimes just give myself a couple more minutes of rest (i.e. soft pedaling) until my heart rate comes down and i can do another. i suppose i should really try to stick to x amount of recovery time and if i can't get my HR down, i should stop.

I think the answer to this differs a great deal from one individual to the next. An important question to ask is how do you feel the day or two days after the workout? If you are too sore to do your planned workout, then you probably rode too hard in the day or two before. If you are just recovering before your next workout, then I think you are doing it right.

good point. i've been recovering pretty quickly lately and my legs are surprisingly fresh most days. it's also hard for me to determine what is actually exercise induced fatigue and what is work\personal life\sleep related. i try to get as much sleep as possible but getting up at 5:30am several days in a row wears me out. i recently added another rest day during the week (now 2) to get additional sleep and it's been much better.