Newsgroup: it.sport.nuoto
Titolo: [EWM][Molto Iper Lungo][Inglese] Hypoxia Training.

"Hypoxia is the term used to identify reduced oxygen supply in blood and 
body tissues. Hypoxic training refers to swimming a repeat distance with a 
restricted breathing pattern in the belief that it will reduce oxygen 
supply. When they swim hypoxic repeats, swimmers do not breathe once during 
each stroke cycle, as is their common practice. Instead, they hold their 
breaths for one or more stroke cycles before taking a breath.
The original purpose of hypoxic training was to simulate training at 
altitude. Proponents thought that reducing the breathing rates of athletes 
would also curtail their oxygen supply and create the same kind of hypoxia 
that takes place at altitude. Research has shown that this assumption was 
incorrect. Several studies have shown that hypoxic training does not reduce 
the oxygen supply to the tissues (Craig 1978; Dicker et al. 1980; Stager et 
al. 1985; Stanford et al. 1985; Van Ness and Town 1989; Yamamoto et al. 
1985). Although some of the studies reported small reductions in alveolar 
oxygen, those effects were not sufficient to simulate conditions at 
altitude.
Despite results like these, hypoxic swimming continues to be a popular form 
of training for competitive swimmers, perhaps because it produces other 
currently unidentified training effects. On the other hand, it may simply be 
that the difficulty of swimming with restricted breathing appeals to coaches 
and athletes because of the effort and discipline it requires. Some coaches 
reason that training that causes so much distress must be doing something 
worthwhile for swimmers.
Beneficial effects are not evident, however, at least as far as aerobic 
capacity is concerned. Because it does not simulate conditions at altitude, 
hypoxic training will not be any more effective than normal training for 
increasing red blood cells or for producing other adaptations that have been 
attributed to training at altitude. One could argue that restricting 
breathing can actually reduce the overall aerobic training effect. When they 
breathe less during long swims or long sets of repeats, swimmers must 
necessarily swim slower so that their muscle pH does not decline too early 
(Van Ness and Town 1989). A compromised oxygen supply will cause more 
production of lactic acid, which in turn will cause greater acidosis at 
slower speeds. Therefore, in trying to cover a long distance with restricted 
breathing, swimmers will have to swim slower than they would while breathing 
regularly. This circumstance could result in at least one unwanted physical 
reaction. They will be swimming slower than they could otherwise swim, so 
their stroke mechanics will be less racelike. If they try to swim at their 
normal training speed, they will create frequent and severe acidosis that 
may damage muscle tissue at a faster rate than it can be repaired. In time, 
they will experience a loss of strength, speed, and endurance.
All athletes have a finite tolerance for acidosis. They can reach that level 
by breathing less and swimming slower or by breathing more and swimming 
faster. I suggest that it is more effective to train by swimming faster 
while still accomplishing the goal of improving endurance. The swimmer's 
stroke mechanics will be more racelike, and acidosis is less likely to 
interfere with the attempt to produce aerobic training effects. Therefore, 
if the swimmer's goal is to improve aerobic endurance, I believe that 
swimming with regular breathing is more reasonable. Swimming with 
unrestrictedbreathing also makes more sense if the goal is to improve 
buffering capacity because the repeats will be more racelike.
Some coaches have suggested that hypoxic training can increase the buffering 
capacities of muscles and blood because of the acidosis that occurs when the 
oxygen supply is reduced. Hypoxic training is unlikely to be any more 
effective than free swimming for this purpose. In fact, it may be less 
effective for the reasons cited earlier, namely, that athletes can swim 
faster and thus with more racelike stroke rates and stroke lengths when they 
breathe regularly. At the same time, swimmers can produce the same degree of 
acidosis with normal breathing that they would produce with hypoxic 
training.
The one adaptation to hypoxic training that surely does take place is an 
improvement in breath-holding ability (Van Ness and Town 1989). Hypoxic 
training produces a condition called hypercapnia, which is an increase of 
carbon dioxide (CO2) in the alveolar air. Hypercapnia produces a strong 
drive to breathe. When a swimmer is having difficulty holding his or her 
breath during races, it is the increase of CO2, not a reduction in oxygen, 
that causes the person to feel starved for air. Frequent breath holding can 
increase a swimmer's resistance to this drive, allowing him or her to resist 
it and swim each length of a race with fewer breaths. For this reason, 
hypoxic training can be a valuable training aid for freestyle sprinters and 
butterfly swimmers, but not for the reasons usually espoused. Backstrokers 
may also gain an advantage from hypoxic training if they use the underwater 
dolphin kick in their races. Breaststrokers have no need for hypoxic 
training because only during turns do they need to hold their breaths. They 
can improve that ability more effectively with drills such as the double 
pulldown drill than they can by hypoxic training.
Swimmers can quickly develop the ability to swim races with fewer breaths. 
Estimates are that only a few weeks of breath-holding training is necessary 
to blunt the drive to breathe produced by a buildup of carbon dioxide in 
tissues. Examples of repeat sets that can improve breath-holding ability 
during sprint races are provided in table 13.6.
Because hypoxic training is physiologically stressful, I recommend that 
swimmers perform it only a few days per week during the season. Sprint 
swimmers should pick a 3- to 4-week period early in the season when they 
emphasize breath holding by doing some form of restricted breathing training 
almost daily. After they have decreased their sensitivity to hypercapnia, 
they should be able to maintain that training effect for the remainder of 
the season with just one or two short breath-holding training sets each 
week."
Kalì.
-- 
Ride History: Garellik 50->Mtx125->Dr650Rs->Sv650s
Riding: Lilith (aka GSX-R 750 my05)
"I miei hobbies sono indipendenti dalle mie morose" © Maz
"Sono ad Affi, dov'è Verona est?" © GSChicco
"Sono al centro Agroalimentare, vieni a prendermi" © GSChicco
"Maz è quello che chatta sempre con Kalì e va piano in moto?" © GenTLe

Kalě wrote:
[cut]
facendo ricordo alle mie (scarse) conoscenze di inglese ho cercato di
leggere quanto da te postato
mi par di capire che come meccanismo di simulazione dell'allenamento in
altitudine il lavoro in ipossia non funzioni
l'unica funzione utile potrebbe essere quella di abituare il nuotatore a
condizioni di ipercapnia simili a quelle delle gare e pertanto puň tornare
utile, a piccole dosi, soprattutto per i velocisti ed in particolare per
liberisti e delfinisti o per i dorsisti che fanno apnee subacquee molto
lunghe
ho colto il senso?
ciao
Vasco

 ho colto il senso?
Sì.


 they will experience a loss of strength, speed, and endurance.
Mi sembra molto interessante anche questo
-- 
PB:  50 sl: 27.37
      50 fa: 29.43 (near to update) (?)
     100 sl: 1.00.29
     100 fa: 1.08.49 (near to update) (?)

 Mi sembra molto interessante anche questo
Il Magli dimostra molto buon senso in parecchi punti del suo librone.
M'ispira un sacco di fiducia.
Probabilmente gli permetterò di allenarmi. :o)


 during sprint races are provided in table 13.6.
c'č modo di vedere questa tabella?
-- 
The only easy day was yesterday
Kaboom?
Yes, Rico. Kaboom.

Castel Chariot <matt...@RIMUOVItiscalinet.it> wrote:

si torna sempre al solito punto: il tipo di nuotata in allenamento deve
essere sempre il più simile possibile a quello che si terrà in gara


 essere sempre il più simile possibile a quello che si terrà in gara
Off course.
Ma mi pareva interessante sottolineare come l'*abuso* di questa tecnica 
potesse essere "dannosa", non ci avevo mai pensato


 potesse essere "dannosa", non ci avevo mai pensato
Ti raccomando le mazzate che "dedica" all'occlusion training ed al nuotare 
spesso sopra soglia.


 c'è modo di vedere questa tabella?
Sì, arriva.


 all'occlusion training
What's?


 What's?
Barbarie: nuotare con lacci agli arti.
Come curiosità posso anche scansire, ma le conclusioni sono _fortemente_ 
contro.


 Sě, arriva.
grazie!


 Barbarie: nuotare con lacci agli arti.
Intendi nuotare con elastici alle braccia che limitano i movimenti???


Table 13.6
Sample Repeat Sets for Improving Breath-Holding Ability
These sample repeat sets can be used for improving breath holding ability in 
50 and 100 freestyle races and for improving underwater dolphin Kicking in 
backstroke and butterfly races.
For 50 races
4 to 8 x 25/1 min send-off. Breathe only once during first several times the 
set is done. Swim with no breath later.
6 x 50/2 min send-off. Several different breathing patterns can be used. One 
breath on each length, or no breath on the first length, 2 breaths on the 
second, or no breath on the first length, 1 breath on the second length.
For 100 races
4 X 100/2 min send-off. Breath every 2, 3, or 4 stroke cycles. 10 x 100/1:30 
send-off. Breath every 2 or 3 stroke cycles. 6 X 200/3 min send-off. Breath 
every 2 or 3 stroke cycles.
6 x 100/2 min send-off. Breathe every stroke cycle during the first 50 of 
each swim and every second or third cycle on the second 50.
4  x 200/3 min send-off. Breathe every stroke cycle on the first 50, every 
second stroke cycle on the middle 100, and every third cycle on the last 50.
Underwater dolphin kicking for backstroke and butterfly races
5  x 25/1 send-off. Underwater dolphin kicks.
4 to 6 X 50/2 min send-off. Kick 15 m underwater on each length. 4 x 100/3 
min send-off. Kick 15 m of each length underwater. 3 x 200/5 min send-off. 
Kick 15 m of each length underwater.
EWM.


"Just beginning to find its way into the programs of competitive swimmers is 
a new form of training known as occlusion training. This method involves 
training with tight, straplike devices around the upper arms or upper legs. 
The purpose of the devices is to occlude, or shut off, part of the blood 
supply. The rationale behind this training is that reducing the blood flow, 
and thus the oxygen and nutrient supply, to muscles will improve their 
adaptations to training. A limited number of studies have investigated the 
effects of occlusion training for both endurance and strength training. The 
results of those studies have been favorable. For this reason, some experts 
have suggested that training with bands on the arms or legs might improve 
both endurance and strength to a greater extent than regular, nonoccluded 
training. I have some doubt about whether this form of training is truly 
beneficial. Let me describe the results of some representative research on 
occlusion training and then discuss why I do not favor this procedure. 
Sundberg (1994) conducted a study in which subjects performed 4 weeks of 
endurance cycling training in which the blood flow was occluded to one leg 
but not the other. A band was placed around one leg, and a pressure of 50mm 
Hg was applied so that the blood flow decreased by 13% to 20%. Several 
measurements were taken on both legs before and after training. These 
included VO2max, exercise time to exhaustion,
capillarization, glycogen storage, strength, enzyme activity, and fiber type 
percentages. As one would expect, both legs improved with training, but in 
all cases the percentage improvements were greater for the occluded leg. The 
percentage increase in VO2max for the occluded leg was nearly double that of 
the nonoccluded leg. The increase in capillaries in the occluded leg was 42% 
greater, and glycogen storage was nearly 10% greater. The activity of 
aerobic enzymes increased by 20% in the nonoccluded leg and by 26% in the 
occluded leg. Occlusion also caused a change in fiber type percentages. The 
percentage of slow-twitch fibers increased by 4% in the occluded leg, 
whereas no change occurred in the percentage of slow-twitch muscle fibers in 
the nonoccluded leg. At the same time, the percentage of FTa muscle fibers 
decreased by 3% in the occluded leg. No change occurred in the percentage of 
FTa fibers in the nonoccluded leg.
The additional improvements in the occluded leg should have had a beneficial 
effect on endurance, and indeed they did. Each leg was tested separately 
before and after training. Work time to exhaustion increased by 25% in the 
occluded leg but by only 13% in the nonoccluded leg.
1 should mention that endurance training produced some effects that would be 
detrimental to sprinting performance in the occluded leg but not in the 
nonoccluded leg. One of the most important of these was that activity of the 
muscle form of the enzyme lactate dehydrogenase (M-LDH) decreased by 25% in 
the occluded leg, whereas no change occurred in the activity of this enzyme 
in the nonoccluded leg. This change would favor the oxidation of pyruvate 
and result in a lower rate of lactic acid production. Another important 
negative training effect was that strength fell by 8% in the occluded leg 
but remained unchanged in the nonoccluded leg. The authors felt the loss of 
strength may have been related to the decrease in size and number of the FTa 
muscle fibers in the occluded leg.
Several other effects of occluded training that could be considered 
detrimental concern the rate of energy use. Reductions in ATP and CP were 
greater in the occluded leg than in the nonoccluded leg during testing, and 
lactate levels were higher in the muscles of the occluded leg. Muscle 
glycogen use was also greater in the muscles of the occluded leg, most 
likely because their supply of blood glucose was restricted. The difference 
in glycogen use was not substantial between slow-twitch muscle fibers. The 
slow-twitch fibers of the occluded leg were 80% depleted of the glycogen 
supply after 45 min of hard exercise, whereas the slow-twitch fibers of the 
nonoccluded leg lost approximately 70% of their glycogen. Differences in 
glycogen use were much more dramatic in the fast-twitch muscle fibers. Those 
of the occluded leg lost approximately 30% of their glycogen supply, whereas 
the fast-twitch fibers of the nonoccluded leg lost approximately 10%.
Researchers have also studied the effect of occlusion with regard to 
strength training. Takarada and coworkers (1998, 2000) reported that human 
growth hormone increased significantly when an occluded body part performed 
several repetitions to exhaustion with a light weight. The same exercise 
produced no significant change in the concentration of this hormone in the 
body when body parts were not occluded {Takarada et al. 1998,2000). 
Increases in human growth hormone should increase muscle size and strength.
In the first of these studies, subjects performed one-arm biceps curls with 
both their right and left arms. One arm was occluded during the training, 
and the blood flow was unobstructed in the other arm (Takarada et al. 1998). 
The training resistance for the occluded arm was 50% of the weight the 
subjects could curl for one repetition, and a resistance of 80% of their 
one-repetition maximum was used for training the nonoccluded arm.
The researchers reported a similar increase in the size of the biceps 
muscles of each arm. Muscular strength increases were also similar in both 
the occluded and nonoccluded arms. They concluded that occluded and 
nonoccluded training were equally effective for increasing muscle size and 
strength but that occluded training can produce the same results with 
considerably lower resistance. Unfortunately, the authors did not include a 
group that trained with low resistance and no occlusion, nor did they test a 
group that trained with high resistance and occlusion. The inclusion of 
subjects in such groups would have permitted us to determine (1) if 
low-resistance, nonoccluded training was as effective as low-resistance, 
occluded training for improving muscle size and strength and (2) if 
high-resistance, occluded training was more or less effective than 
high-resistance, nonoccluded training for the same purposes.
From these results, one could argue that several aerobic and anaerobic 
training effects can be produced more effectively with occlusion than with 
regular, nonoccluded training. I have doubts about this proposition, at 
least for swimming training, for three principal reasons:
1.  Athletes can produce improvements of the same magnitude as those 
resulting from occlusion training simply by training at a higher intensity 
with no occlusion. In addition, training with a greater intensity should be 
more effective in other ways. The first part of this statement seems evident 
from the weight-training study. Subjects got the same results with their 
nonoccluded arm by training at 80% of their one-repetition maximum as they 
did by training the occluded arm with lighter weights. The reason that 
training at a higher intensity should be more effective is that athletes 
will be training at faster speeds that are closer to those they use in 
competition. Athletes would have to swim more slowly during occluded 
training because of the additional energy use and lactic acid accumulation. 
Such slow speeds and slow stroke rates would not be conducive to maintaining 
the stroke rates and paces for competition.
2.   Occlusion training seems to produce more effects that many people would 
consider negative in regard to long-term training. Faster rates of muscle 
glycogen use would result in the need for more recovery swimming to provide 
time for replacement. This requirement would reduce the average training 
intensity for each week, and athletes would not be able to swim threshold, 
overload, and race-pace sets as often. Trying to train intensely when muscle 
glycogen is low could also cause swimmers to lose some of their muscle 
tissue, which would ultimately reduce their strength and power. Higher rates 
of lactic acid accumulation could also cause more muscle damage, which would 
further increase the amount of recovery training swimmers would need each 
week. Another negative effect is that endurance-oriented occlusion training 
might reduce muscle strength and anaerobic power more than normal training 
would. Loss of strength and anaerobic power would cause a loss of speed that 
could be detrimental to middle distance and
sprint swimmers. Finally, occlusion training may upset the delicate balance 
between lactate production and removal during exercise, causing more lactic 
acid to be produced at slower speeds and less to be removed from the 
muscles.
3. Perhaps the most compelling argument against occlusion training for 
swimming concerns the muscles affected. Occlusion training would affect only 
the muscles of the legs and arms. Athletes wear the bands that restrict 
circulation near the top of each thigh and just below the shoulder of each 
arm. This placement means that the large muscles of the shoulders, trunk, 
back, and hips, which provide most of the propulsive force for swimmers, 
would be largely unaffected by the occlusion. Consequently, the blood supply 
to the muscles that do most of the work in competitive swimming would not 
decrease.
I believe that the arguments against endurance-oriented occlusion training 
are persuasive, despite the fact that occlusion training appears to be 
effective for producing certain physiological adaptations. The arguments 
against using it for sprint training are even stronger. The more effective 
way to stress anaerobic metabolism and power production should be by 
swimming faster rather than swimming slower. When athletes swim faster in 
training, they will be using combinations of stroke rates and stroke lengths 
similar to those they use in races. In addition, the sensations they monitor 
for decreasing drag will also be similar to those they experience in 
competition. Additionally, occlusion training may be detrimental for 
improving the rate of anaerobic metabolism. Fast stroke rates and the 
application of substantial muscular force will stimulate the rate of 
anaerobic metabolism more than will swimming with slower rates and less 
force. In short, an evaluation of the physiological responses that occlusion 
produces suggests to me that occlusion training is not a viable procedure 
for competitive swimmers. In the long run, it has the potential to do more 
harm than good."
EWM.


"Running and other land activities such as running hills and stairs have 
become common early season activities in some swimming programs. Many 
coaches and athletes believe that these activities will enhance endurance 
beyond what athletes could achieve by swimming alone. Running will certainly 
produce central adaptations that can improve a swimmer's aerobic capacity. 
Running will train the circulatory and respiratory systems, causing 
improvements in cardiac output, stroke volume, tidal volume, and pulmonary 
diffusing capacity, which will improve oxygen delivery during swimming. 
Running may do this as well as swimming itself does. Running will also 
produce adaptations in the muscles of the legs, such as increased 
capillarization, improved blood shunting, and increases in size and number 
of mitochondria. But swimming can produce all these adaptations equally 
well. More important, swimming will produce significant training effects in 
the muscles of the upper body. These are the muscles crucial to success in 
most competitive strokes, and running cannot produce significant training 
effects in them.
One might wonder how running became such a popular part of many swimming 
programs. The rationale for including running in the training of swimmers 
was originally based on research in which trained subjects achieved higher 
heart rates and higher rates of oxygen consumption when running than when 
swimming (Holmer 1974). Unfortunately, some people interpreted these results 
to mean that running was superior to swimming for improving aerobic 
endurance. That conclusion, however, is incorrect. The results of the study 
demonstrated only the principle of specificity. Most of the subjects in 
Holmer's study were trained runners; only a few were trained swimmers. No 
one noticed that Holmer also reported that the competitive swimmers in the 
group achieved higher heart rates and maximal oxygen consumption values when 
swimming than the runners were able to achieve.
Other studies have repeatedly supported the position that athletes make the 
greatest improvement in oxygen consumption by specific training {Magel et 
al. 1975; McArdle et al. 1978; Pechar et al. 1974). In one of these, Magel 
and his associates (1975) trained 15 men for 1 hr per day, 3 days per week, 
over a 10-week period with standard swimming repeats. Each subject's VO2max 
was measured before and after training, while they were swimming and while 
they were running on a treadmill. Swimming VO2max increased by 11%, and 
swimming times to exhaustion increased 34%. In contrast, the subjects showed 
no improvement in running VO2max.
Competitive swimmers should use running only as a supplemental form of 
training, never as a substitute. Any swimmer who substitutes running for 
swimming to improve aerobic capacity should understand that the results will 
be inferior to those he or she could achieve by expending the same time and 
effort in swim training.
Running uphill or running up stairs is not advised for swimmers under any 
circumstances. The only improvements swimmers can hope to achieve from 
running up stairs will occur in the leg muscles used for running. No 
improvement will occur in the muscles of their upper bodies. At the same 
time, leg muscles that are more active in swimming than in running will not 
receive the same training benefit that would result from swim training. I 
believe that swimmers could more profitably spend the time they devote to 
running uphill and up stairs to doing kicking drills to improve the speed 
and endurance of their leg muscles. As far as land activities are concerned, 
exercises that increase leg extension power, such as plyometric jumps, 
vertical jumps, and power leg extension exercises with weights, should 
provide greater improvement in leg power for starting and turning than 
running uphill or running up stairs could produce.
Finally, running uphill and up stairs can be dangerous. Falling injuries are 
common. Some of these may require the athlete to take a few days off for 
healing, but others can be so serious that they curtail training for a good 
portion of the season. Injuries to the ankles, knees, and hip joints may 
occur because of the tremendous effort required to lift one's body weight 
explosively with one leg.
Although members of both sexes are susceptible to leg injuries from uphill 
running and, especially, from running stairs, the incidence of such injuries 
is likely to be greater among females than among males. Women, on average, 
have looser joints and smaller ligaments and tendons. In addition, fat makes 
up a greater percentage of their body weight, and muscle a smaller 
percentage. These differences between the sexes cause females to be more 
susceptible to injuries from activities in which they have to support their 
body weight. In addition, females generally have wider hips than males, 
which increases the angle between the long bone of the upper leg, the femur, 
and one of the two long bones of the lower leg, the tibia. When a female 
flexes her leg, that larger angle between the bones of the upper and lower 
leg permits the kneecap, or patella, to move laterally farther than it would 
in a male. Females are thus more susceptible to knee injuries, particularly 
dislocations of the patella (Wells 1985). I do not recommend including stair 
running in the training programs of swimmers, particularly female swimmers."
EWM.


 swimming than the runners were able to achieve.
Questo pare fuori dall'esperienza che molti di noi anno.
Comunque stavolta non mi ha convinto completamente per quanto riguarda 
l'inutilità della corsa (a piccole dosi).
Per esempio non analizza possibili controindicazioni in termini di 
adattamento sul fare grandi lavori aerobici in acqua (e qua si torna al 
caro discorso sul nuotare molto fuori dalle andature di gara).


 l'inutilità della corsa (a piccole dosi).
Uè, come contraltare mette dedicare quel tempo a tecnica solo gambe: 
sticazzi se convince!!!
Kalì.


 sticazzi se convince!!!
Quello per quanto riguarda la corsa in salita o i gradoni


 harm than good."
Ma questo mi pare condivisibile, e penso che valga per la maggior parte 
di tutti i metodi di allenamento "alla rocky"


Kalě wrote:
pur avendone letto, lo ammetto, solo una parte, devo dire che mi sembra
follia pura
qui stiamo rasentando pratiche di masochismo, altro che allenamento
questa perversione manco sapevo che esistesse e non ne sentivo affatto la
mancanza
piuttosto vorrei chiarire un punto che hai citato nel post precedente, oltre
all'occlusion training dicevi che Maglisco parla male del nuotare spesso
sopra soglia
giusto per chiarezza, cosa intende con questo?
piů velocemente della soglia o con tempi piů alti (quindi piů lentamente)
della soglia?
insomma critica chi fa troppo spesso lavori anaerobici (magari per lo stesso
motivo che ha colpito Castel, e cioč per gli effetti negativi dell'acidosi
protratta sui muscoli) o chi si allena troppo lentamente?

 giusto per chiarezza, cosa intende con questo?
Visti i numerosi stralci da questo capitolo (13 - Endurance Training) sto 
preparando un documento che lo contenga integralmente, da decidere come 
divulgarlo visto che non penso il NG adatto per post estensivi come quelli 
fatti tra ieri ed oggi.
Una mail list è più discreta ed appropriata. ;o)
Cmq, come da subj ecco la parte che ti interessa:
"I have attempted to explain why it is necessary to do some very fast 
training to improve aerobic endurance to a maximum level. Doing so too 
often, however, can produce the opposite effect. The results of several 
studies suggest that athletes can actually lose endurance by swimming faster 
than threshold speeds too frequently in training.
Madsen and Olbrecht (1983) reported that athletes who trained at speeds that 
produced blood lactate concentrations in the neighborhood of 6 mmol/L (which 
was probably above the anaerobic threshold for most of the athletes) 
exhibited deteriorations in performance on measures of aerobic endurance. 
Hollmann and coworkers (1981) reported that subjects who trained for 6 weeks 
at blood lactates in excess of 4 mmol/L, which is also above the anaerobic 
threshold for most athletes, did not improve their aerobic endurance. Heck 
and his associates (1985) reported similar results when subjects trained for 
20 weeks at speeds above those that produced blood lactates of 4 mmol/L.
In another study designed to investigate the effects of training above the 
anaerobic threshold, Gabriel and coworkers (1998) found that subjects 
"suffered from typical overtraining symptoms" after just 4 weeks of training 
at speeds above those corresponding to their anaerobic thresholds. In 
addition, their performance declined 3% on a maximum effort test of 60 sec 
and by 14% on a test of time to exhaustion at a pace equal to 110% of each 
subject's anaerobic threshold. Urhausen and associates (1998) also reported 
decrements in performance after 4 weeks of training above the anaerobic 
threshold. In addition, they disclosed that training above the anaerobic 
threshold caused a significant decline of 20% to 42% in the secretion of 
several hormones, including epinephrine, norepinephrine, and growth hormone. 
Mikesell and Dudley (1984) also reported that runners who did their 
endurance training at fast speeds lost aerobic capacity.
Four principal reasons explain why aerobic capacity may deteriorate if an 
athlete trains above the anaerobic threshold too frequently. First, intense 
training reduces the quantity of endurance work that the athlete can 
accomplish. When swimmers complete training sets above the anaerobic 
threshold, a steady increase of muscle lactate occurs that reduces pH and 
causes fatigue within 10 to 20 min. After swimmers become fatigued, they 
will probably require 10 to 30 min of easy swimming before muscle pH will 
normalize and they will be able to perform another intense set of repeats 
(Hermansen and Osnes 1972). So, swimmers spend a small amount of time 
swimming fast and a large amount of time swimming at recovery levels that 
are too slow to improve aerobic capacity. The slow speeds are usually 
inadequate for overloading aerobic metabolism, and the swimmers cannot 
maintain fast repeats long enough to overload aerobic metabolism adequately.
The second reason that frequent training at speeds beyond the anaerobic 
threshold can be detrimental concerns the effect on slow-twitch muscle 
fibers. As I described earlier, evidence suggests that swimming faster than 
threshold speed may reduce some aspects of aerobic capacity in slow-twitch 
muscle fibers even as it improves the aerobic capacity of fast-twitch muscle 
fibers. This finding reinforces the importance of training at speeds both 
slower than and faster than threshold speeds. Training in that way can 
increase the aerobic capacity of all muscle fiber types. A third reason may 
be the effect of training with low levels of muscle glycogen. One or two 
repeat sets swum near anaerobic threshold speed or faster will considerably 
reduce muscle glycogen. If athletes try to swim fast in subsequent training 
sessions before their muscle glycogen has been replaced, they will burn 
significantly greater amounts of protein for energy, cannibalizing their own 
muscle tissue for energy. The muscle will lose some mitochondria that 
provide their endurance and some structural proteins that give them strength 
and power. When that loss becomes extensive, performance will suffer.
  The fourth reason concerns wear and tear on the endocrine and immune 
systems and the potentially damaging effects of severe and frequent acidosis 
on muscles. Several pieces of research have shown a reduction in the 
secretion of certain hormones, principally human growth hormone and the 
hormones of the adrenal glands involved in the fight-or-flight reaction - 
cortisol, epinephrine, and norepinephrine - when athletes overtrain. The 
adrenal hormones are involved in the fight-or-flight reaction that prepares 
the body for exertion. Training faster than threshold pace initially causes 
an increase in secretion of these and other hormones. Over time, however, 
the rate of secretion decreases. These reductions in secretion are usually 
accompanied by symptoms of overtraining, including decreased performance, 
weight loss, lack of interest, and lowered motivation. Because growth 
hormone stimulates tissue growth and the adrenal hormones facilitate the 
release of energy from glycogen and fat, their suppression may cause a 
reversal of training adaptations and a reduction in performance. A reduction 
in the adrenal hormones will also make it difficult for athletes to mount 
maximum efforts in training and competition.
Experience and the available evidence suggest that athletes should not swim 
at threshold speed and faster too often. They should be sure to provide 
sufficient time to replace the glycogen their muscles used for energy during 
those sets, repair the damage to the muscles, and replenish the hormones 
they used."
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 Cmq, come da subj ecco la parte che ti interessa:
quindi è nuotare troppo spesso ad alta velocità che può creare problemi
insomma, alla fine è il solito problema di trovare il giusto equilibrio
grazie per la disponibilità
ciao
Vasco

 insomma, alla fine è il solito problema di trovare il giusto equilibrio
Si, direi che la questione è sempre la stessa.
L'acidosi è velenosa per il muscolo, ergo bisogna alternare gli allenamenti
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