Lactic threshold worsens with fatigue?

carbonmanx

I'm currently working on improving my hill climbing speed and endurance, I can get up most hills currently albeit slowly i live near sidmouth so peak hill and salcombe hill are good training grounds for me.

I understand what lactic threshold is I think, but I dont understand why this gets less and less as I get more and more tired.

i.e I can be 5 miles into a ride, hit peak hill say, and climb up it relatively pain free, if I then hit it again 20 miles later, the burn in my quads kicks in considerably quicker. I'm obviously more tired, but from what I understand about the process which creates the lactic acid, I dont understand why this gets worse the longer the ride - to the point where eventually I wouldnt be able to climb the hills because I burn out so early.

If that makes any sense, does anyone have an explanation as to why the above happens, and more importantly, how can I improve / reduce that fatigue related burn?

Thanks in advance :-)

colinsmith123

I'm no expert, so I have copied this from my lab test taken in March of this year. Hopefully this goes some way towards answering your question and find useful.

Your lactate threshold occurred at (deleted) W. This point represents the intensity in an incremental exercise test where blood lactate concentration ([La]) suddenly begins to increase above the resting concentrations and reflects an increased rate of anaerobic metabolism (hence the concept of the ‘anaerobic threshold’). However, the lactate threshold does NOT represent the onset of ‘anaerobic’ metabolism (lactate is actually produced below the lactate threshold), but it does indicate the first point at which significant changes in the body occur. One of the main reasons your breathing rate increases noticeably and sharply during incremental exercise of this type is because of the accumulation of lactate in the bloodstream – the body has to breathe harder and faster to get rid of the excess carbon dioxide this lactate produces.

The intensity that corresponds to this first ‘threshold’ usually lies somewhere between 50 and 70% of the maximal oxygen uptake, with less-well endurance trained individuals being closer to the lower percentage. A world-class time-triallist may have this point at 80% of their VO2 max whereas in a poorly conditioned sedentary person this may be as low as 40%. By raising this point to a higher percentage this would allow you to sustain a greater percentage of your maximal capacity without fatigue and in turn allow a sizeable increase in sustainable power in longer races. (Contrary to popular belief, lactate itself does not directly cause muscle fatigue; in fact, lactate should really be regarded as the consequence of muscle fatigue, not the cause of it).

jibberjim

The burn in your quads has nothing to do with your lactic threshold. It's down to fatigue, it's linked of coure, as to generate the fatigue, you probably need to work really hard and hence rely on lactic energy systems. Your second time up it, more of your muscle fibres are fatigued, so your body can't just recruit others but has to force already tired ones to work.

There are also loads of "lactic thresholds" and no two people would agree on what it means, the example colinsmith123 pasted would have little to do with climbing peak hill (but a lot to do with a flat 100mile TT)

carbonmanx

that makes more sense - i had always associated the muscle "burn" when you are doing something for a prolonged period - hill climbing, repeated squats etc.. as a lactate ? (lactic?) burn...

if its just my muscles going arrgghhh im tired, then it makes much more sense why the longer I ride the more readily I get that burn...

Presumably the only way the combat that then is to build up my stamina / keep hydrated and well energized through regular carb intake etc..?

Thanks

jibberjim

You can also lower the forces required - since creating high forces requires more "motor units" - your muscle fibres and the more you need each time the more you have to rely on fatigued ones. Which you can do by spinning more - of course that's not going to be easy up Peak Hill (I had to stop for a rest on the driveway last time I did it) whatever gears you take are not going to be that helpful, but if there is any scope at the moment it will likely help.

carbonmanx

Thanks a good point, I think I am hitting my legs threshold before my aerobic one.. So I might try spinning more which will use more of my lungs and might give my legs a better chance...
Will see how it goes!
Thanks for the advise.

Team4Luke

20 miles later is probably over an hours riding and your probably doing that section at such effort your generating even more fatigue/latic before you hit that hill again. Try riding steadier over the whole ride and your effort will span out and eventually you will do your ride faster. Use what tools you have and keep it your pace steady and constant, so look at HR, speed, Watts, Cadence.