Specificity of training adaptation

[Guest guest]

The below seems relevant to recent discussions:

Specificity of training adaptation: time for a rethink?

A. Hawley (2008)

Specificity of training adaptation: time for a rethink?

The Journal of Physiology 586 (1), 1–2. Excerpts provided:

....The key components of any training programme are the volume (how

much), intensity (how hard) and frequency (how often) of exercise

sessions. These `training impulses' determine the magnitude of

adaptive responses that either enhance (fitness) or decrease

(fatigue) exercise capacity (Hawley, 2002). A long held view is that

the training response/adaptation is directly related to the volume of

exercise undertaken (Fitts et al. 1975). However, there is obviously

a threshold volume/duration beyond which additional stimuli do not

induce further increases in functional capacity. This `biological

ceiling' is important because it implies that the regulatory control

mechanisms signalling adaptive responses are ultimately titrated by

exercise duration (Booth & , 1985).....

One of the key tenants of exercise physiology is the principle of

training specificity, which holds that training responses/adaptations

are tightly coupled to the mode, frequency and duration of exercise

performed (Hawley, 2002). This means that the vast majority of

training-induced adaptations occur only in those muscle fibres that

have been recruited during the exercise regimen, with little or no

adaptive changes occurring in untrained musculature....

In this issue of The Journal of Physiology, the results of study by

Burgomaster et al. (2007) force us to rethink some of our long held

beliefs regarding the concept of training specificity and

response/adaptation, as well as providing a reminder that for certain

individuals, very intense training can be a time-effective and potent

stimulus for inducing many of the benefits normally associated with

more prolonged, submaximal endurance-type workouts....

In their recent investigation Burgomaster et al. (2007) report that 6

weeks of low-volume, high-intensity sprint training induced similar

changes in selected whole-body and skeletal muscle adaptations as

traditional high-volume, low-intensity endurance workouts undertaken

for the same intervention period. Specifically, they show that four

to six 30 s sprints separated by 4–5 min of passive recovery

undertaken 3 days per week results in comparable increases in markers

of skeletal muscle carbohydrate metabolism (i.e. total protein

content of pyruvate dehydrogenase), lipid oxidation (i.e. maximal

activity of â-3-hydroxyacyl CoA dehydrogenase) and mitochondrial

biogenesis (i.e. maximal activity of citrate synthase and total

protein content of the peroxisome-proliferator-activated receptor-ã

coactivator-1á) as when subjects undertook 40–60 min of continuous

submaximal cycling a day for 5 days per week. These findings are

particularly impressive given that weekly training volume was 90%

lower in the sprint-trained group (225 versus 2250 kJ week & #8722;1)

resulting in a total cumulative training time of 1.5 versus 4.5 h per

week.....

As with all studies, one should use caution when extrapolating the

results beyond the specific conditions of the investigation.....

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Similar metabolic adaptations during exercise after low volume sprint

interval and traditional endurance training in humans

Kirsten A. Burgomaster, Krista R. Howarth, Stuart M. , Mark

Rakobowchuk, Maureen J. Mac, L. McGee, J. Gibala

(2008)

The Journal of Physiology 586 (1), 151–160.

Low-volume `sprint' interval training (SIT) stimulates rapid

improvements in muscle oxidative capacity that are comparable to

levels reached following traditional endurance training (ET) but no

study has examined metabolic adaptations during exercise after these

different training strategies.

We hypothesized that SIT and ET would induce similar adaptations in

markers of skeletal muscle carbohydrate (CHO) and lipid metabolism

and metabolic control during exercise despite large differences in

training volume and time commitment. Active but untrained subjects

(23 ± 1 years) performed a constant-load cycling challenge (1 h at

65% of peak oxygen uptake before and after 6 weeks of either SIT or

ET (n = 5 men and 5 women per group). SIT consisted of four to six

repeats of a 30 s `all out' Wingate Test (mean power output 500 W)

with 4.5 min recovery between repeats, 3 days per week. ET consisted

of 40–60 min of continuous cycling at a workload that elicited 65%

(mean power output 150 W) per day, 5 days per week. Weekly time

commitment (1.5 versus 4.5 h) and total training volume (225 versus

2250 kJ week & #8722;1) were substantially lower in SIT versus ET.

Despite these differences, both protocols induced similar increases

(P < 0.05) in mitochondrial markers for skeletal muscle CHO (pyruvate

dehydrogenase E1á protein content) and lipid oxidation (3-hydroxyacyl

CoA dehydrogenase maximal activity) and protein content of peroxisome

proliferator-activated receptor-ã coactivator-1á.

Glycogen and phosphocreatine utilization during exercise were reduced

after training, and calculated rates of whole-body CHO and lipid

oxidation were decreased and increased, respectively, with no

differences between groups (all main effects, P < 0.05).

Given the markedly lower training volume in the SIT group, these data

suggest that high-intensity interval training is a time-efficient

strategy to increase skeletal muscle oxidative capacity and induce

specific metabolic adaptations during exercise that are comparable to

traditional ET.

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Carruthers

Wakefield, UK