Bill Nye the Sport Science Guy wrote:
I would agree glycogen depletion is associated with fatigue - but I don't necessarily agree it is always associated with acidosis. For example - if you deplete glycogen content in muscle with prolonged, moderate-intensity exercise, you're unlikely to induce a significant strain on the pH of muscle.
Elite athletes will have glycogen values of ~700-800 mmol/kg dry weight muscle. Maximal intensity exercise (think 400-600m all out) has a rate of glycogen depletion of ~100 mmol/kg dry weight/minute, which drops to ~40 mmol/kg/minute for most mid-distance event durations. It has been suggested that you need to drop below 250-300 mmol/kg to impair function. This would suggest you are highly unlikely to deplete glycogen across the entire muscle in middle distance events lasting 100-780 seconds (1:40-13:00 mm:ss).
In contrast, it's entirely possible to deplete glycogen in an event like the marathon, despite lactate levels never exceeding 4 mmol. But yes you are correct - lactate production consumes a H+ ion, but this occurs regardless of where the glucose comes from (glycogen or blood glucose).
As for those speeds: 9 m/s is 540m/60s. That's ~44sec 400m pace.
·Hocker closed the lasted 300m in Paris in ~39.65, which is ~7.6m/s. El Guerrouj also closed the last 300m in ~39.77 when he ran 3:26.
·The fastest 100m in both the Wanamaker Mile (Cam Myers) and the Dr. Sanders 3000m (Grant Fisher) was slightly slower, at ~13.6 s (7.4 m/s).
·Rudisha's opening 200m during the 2012 Olympics was his fastest at ~23.4s, which is ~8.5 m/s.
So while top tier athletes they may potentially hit the speeds you've mentioned as an absolute peak speed, they are absolutely not holding 9-10 m/s for any significant portion of time even when running World/Olympic Records.
I'm talking about glycogen depletion in the most powerful muscle fibers in the shorter distance races. I stated that implicitly. I don't know why it confuses you, it's an obvious point.
Regarding blood glucose versus muscle glycogen, Robergs et al state:"For the production of 2 pyruvate, there is a net release of 2 protons when glucose is the source of G6P, and 1 proton when glycogen is the source. Using glycogen as the source of G6P, as opposed to blood glucose, is less acidifying to muscle during intense exercise"
Regarding the speed of athletes, Yes, I was referring to top speed. Hocker is much faster than my best over 100m. He obviously has more fast twitch fibers than me. This should be obvious from my post.