REF-1601 · Beneke et al., 2005 · Journal of Applied Physiology · Paper · PubMed

After a 30-s all-out Wingate test, blood lactate in 12 young men kept rising for about six minutes, peaking at 13.7 ± 1.4 mmol/L at 5.7 ± 1.1 min, and the modelled rate at which lactate left the blood (about 0.020 per min) means the extra lactate halves only about every 35 min (our arithmetic); boys peaked lower and sooner and cleared faster. From the abstract

Main caveat: Written from the abstract: blood sampling times, recovery activity and training status are not given.
limited evidenceMeasured on a mixed groupRead from the abstract only

Beneke and colleagues asked whether children's lower blood lactate after short maximal exercise reflects different kinetics.

Fifteen prepubescent boys, 12 adolescents and 12 adults did a Wingate test, and each blood lactate curve was fitted with a biexponential model with four parameters: the lactate generated outside the blood (A), a rate constant for lactate entering the blood (k1), a rate constant for it leaving the blood (k2), and from these the peak blood lactate (BLCmax) and the time it was reached (TBLCmax).

The boys' peak was lower and earlier than that of adolescents and adults. Lactate generated per unit of muscle mass and k1 did not differ between groups, while k2 was higher in the boys. The authors conclude that the age differences are unlikely to come from how much lactate muscle produces or how fast it enters the blood, and partly come from faster removal from the blood.

Participants

GroupnAge (yr)Height (m)Body mass (kg)
Prepubescent boys1512.0 ± 0.61.54 ± 0.0640.0 ± 5.2
Adolescents1216.3 ± 0.71.83 ± 0.0768.2 ± 7.5
Adults1227.2 ± 4.51.83 ± 0.0681.6 ± 6.9

Male (MEDLINE indexing); training status not given.

Protocol

Exercise: a Wingate anaerobic test (30 s all-out).
Model: biexponential, four parameters: A (lactate generated in the extravascular compartment), k1 (entry into blood), k2 (exit from blood), giving BLCmax and TBLCmax.
Blood sampling times and the activity during recovery are not described in the abstract.

Key Results

ParameterBoysAdolescentsAdults
BLCmax (mmol/L)10.2 ± 1.312.7 ± 1.013.7 ± 1.4
TBLCmax (min)4.1 ± 0.45.5 ± 0.75.7 ± 1.1
A per muscle mass (mmol/L)22.8 ± 2.722.7 ± 1.324.7 ± 2.8
k1 (per min)0.865 ± 0.1150.692 ± 0.2210.687 ± 0.287
k2 (per min)0.0287 ± 0.00750.0203 ± 0.00890.0199 ± 0.0093
ln 2 / k2, half-time of the late fall (min; our arithmetic)about 24about 34about 35
BLCmax and TBLCmax were lower in boys than in adolescents and adults (P < 0.05); k2 was higher in boys (P < 0.01); A per muscle mass and k1 did not differ.
Our arithmetic: at the adults' mean k2 plus or minus one SD, the half-time spans roughly 24 to 65 min, so individuals differ widely. Reading k2 as the rate of the late fall assumes that the much faster entry phase (k1 about 0.7 per min, a half-time near 1 min, our arithmetic) is over, which is how a biexponential curve behaves (inference from the model's form).

Practical Application

Blood lactate is a slow clock and a poor gate for starting intervals: after a 30-s all-out test in 12 young men it was still rising until about six minutes after the effort, and the modelled clearance halves the extra lactate only about every 35 min (our arithmetic), far slower than power recovers ([REF-809], [REF-480]).
Inference, not tested here: a lactate reading taken in the first minutes after a hard effort is still on the way up, so it understates the peak and says nothing yet about recovery.
What the base uses instead of a lactate number: on an SFT day, 3-5 min easy after the test and then the decision (practice, SYNTH-66), with the test read as output, RPE and heart-rate recovery together (SYNTH-41).
An active cool-down clears blood lactate faster but was largely ineffective for next-day performance (REF-913); this study did not compare recovery modes.
In boys the extra lactate cleared faster (half-time about 24 min, our arithmetic) and peaked lower (SYNTH-81 for the teenage rider).

Limitations

Written from the abstract: blood sampling times, recovery activity and training status are not given.
The time course is modelled; the half-times are our arithmetic from the group means.
Twelve adults, males only by indexing.
One kind of effort: a 30-s maximal test.
The spread in k2 is large (SD close to half the mean).
How this entry was checked and changed
Why this level

a cross-sectional measurement study with 12 adults (39 in all); blood lactate kinetics are the subject, so the marker step does not apply (rule 3)