CHAPTER 11 CARDIORESPIRATORY TRAINING: PROGRAMMING AND PROGRESSIONS | ACE PERSONAL TRAINER MANUAL
At higher intensities, when the buffering mechanism cannot keep up with the extra acid production, and the pH of the blood begins to fall (due to accumulating lactate), the respiratory center is strongly stimulated, and there is yet another increase in breathing (VT2) (see Figure 11-4). This is usually associated with a blood lactate concentration of about 4 mmol/L (this blood lactate concentration is equivalent to the OBLA) (Sjodin et al., 1982; Sjodin & Jacobs, 1981). This point represents the intensity at which the body can no longer sustain an activity, given the accumulation of lactate, and begins to shut down. In most healthy people, this marker is associated with a flattening of the HR response to increasing intensity, referred to as the HR turnpoint (HRTP) (Figure 11-5).
Figure 11-5
Schematic of the detection of the first and second thresholds based on increases in ventilation (VT1 and VT2), on lactate (4 mmol/L), and on the non-linearity of the HR increase. This provides for the possibility of three effective training zones based on two thresholds.
20
HR/10 V•
E/10 15 10 5 0 Lactate ZONE 1
THRESHOLD DETECTION ZONE 2
ZONE 3 VT2 & 4 mmol & HRTP
VT1
| 0
| 25
| 50
| 75
| 100 OUTPUT (W)
Note: VT1 = First ventilatory threshold; VT2 = Second ventilatory threshold; HR = Heart rate; V•
E = Minute ventilation; mmol = millimols; HRTP = Heart rate turnpoint; W = Watts
| 125
| 150
| 175
| 200
KEY CONCEPT
These two metabolic markers—VT1 and VT2—whether based on respiratory responses or blood lactate responses, provide a convenient way to divide intensity into training zones that are determined without any use of, or reference to, MHR (Figure 11-6): • Zone 1 (low to moderate exercise) reflects heart rates below VT1. • Zone 2 (moderate to vigorous exercise) reflects heart rates from VT1 to just below VT2. • Zone 3 (vigorous to very vigorous exercise) reflects heart rates at or above VT2.
Figure 11-6 Three-zone intensity model
VT1 ZONE 1 ZONE 2 Note: VT1 = First ventilatory threshold; VT2 = Second ventilatory threshold VT2 ZONE 3
