We compared physiological responses corresponding to speeds at plasma lactate markers
between incrementa
l treadmill running of 4 and 8
min
stages in fifteen
healthy men (23 ± 4
yrs
, 1.78 ± 0.49 m, 72.7 ± 10.8 kg).Treadmill speed, oxygen uptake (
V
O
2
), heart rate (HR),
rating of perceived exertion (RPE) and plasma lactate were measured for each stage, and
calculated at: fixed blood lactate accumulation (FBLA) 4.0
mmol/L
, an initial 1
mmol/L
rise,
deviation maximum (D
max
), lactate t
hreshold (LT) and log
-
log LT.
There was no effect
(
p
>0.05) of stage duration on speed,
V
O
2
, HR
and RPE at fixed markers. For 8 min
stages,
speed was lower at modelled markers: D
max
(
-
1.1 km/
h;
p=
0.001), LT (
-
0.9
km/
h
;
p=0
.008)
and log
-
log LT (
-
0.8
km/h;
p=0
.006), yet RPE was higher and
V
O
2
lower for LT (1.1,
p=
0.02
;
-
0.27 L/
min,
p=
0.01
) and log
-
log LT (1.4,
p=
0.03
;
-
0.29
L/min
,
p=
0.002). Lactate and
V
O
2
were greater at 8
km/h
for 4 min
(
p=
0.000
1), then similar until 11
km/
h
, with a trend
towards elevated plasma lactate
for 4 min
thereafter.
When applying
lactate
threshold
markers to assess physiological responses to incremental running, protocols using prolonged
stage durations may underestimate
marker running spee