The use of the self-paced exercise test in assessing cardiorespiratory fitness in runners

The aim of this thesis was to investigate the utility of the self-paced exercise test (SPXT) in assessing the cardiorespiratory fitness of runners. Traditionally, cardiorespiratory fitness is assessed via an open-ended graded exercise test (GXT) which utilises fixed increments of work-rate and involves the participant continuing until volitional exhaustion. The SPXT is a closed-looped 10 minute (min) test which is made up of 5 x 2 min stages in which intensity is clamped by ratings of perceived exertion (RPE). The test starts at RPE 11, and this increases in an incremental fashion to encompass RPE 13, 15, 17, and finally 20. The test is more time-efficient than traditional protocols due to not requiring a known starting speed. Additionally, the SPXT may be more valid for runners compared to the GXT in which test duration is unknown.

In study one, gradient and speed-based SPXT protocols were compared to a laboratory based GXT to investigate the validity of the SPXT in producing maximal oxygen uptake (V?O2max). The gradient-based SPXT [which has not previously been investigated] produced higher V?O2max than the GXT (71 ± 4.3 vs. 68.6 ± 6.0 mL·kg-1·min-1, P = .03, ES = .39) but the speed-based SPXT produced similar V?O2max to the GXT (67.6 ± 3.6 vs. 68.6 ± 6.0 mL·kg-1·min-1, P = .32, ES = .21). Results also demonstrated that the oxygen (O2) cost of ventilation may differ between the SPXT and GXT (26.4 ± 2.8 vs. 28.2 ± 2.8 mL.min-1, respectively) (P = .02).

In study two, the oxygen cost of breathing during the SPXT was investigated. When assessed via separate ventilation trials, there were no differences in the oxygen cost of breathing between the SPXT and GXT (26.1 ± 5.3 vs. 26.9 ± 4.2 mL.min-1, respectively) (t7 = -1.00, P = .34,), and V?O2max was again similar between the SPXT and GXT (Z = -.43, P = .67,). The mean velocity at RPE20 (vRPE20) measured via the SPXT was also similar to the maximal velocity (Vmax) derived from the GXT (t8 = .74, P = .48).

In study three, the ability of the SPXT to provide novel parameters that could be used to prescribe six-weeks of running training for recreationally active runners was investigated. Results demonstrated that vRPE20 was effective in improving V?O2max (6 ± 6 %), critical speed (3 ± 3 %) and lactate threshold (7 ± 8%) and these improvements were similar to a separate group who trained using GXT-derived parameters including Vmax (4 ± 8, 7 ± 7, 5 ± 4 %, for V?O2max, critical speed, and lactate threshold, respectively). Prescribing training via the SPXT may be beneficial as it does not require additional testing that is usually associated with the GXT.

In study four, the ability of the SPXT to accurately determine ventilatory thresholds (VT) was investigated. The first and second VT (VT1 and VT2, respectively) were not significantly different when measured as V?O2 between the SPXT (4.03 ± 0.5 and 4.37 ± 0.6 L.min-1, for VT1 and VT2, respectively) and GXT (4.18 ± 0.5 and 4.54 ± 0.7 L.min-1, respectively) in highly trained runners. In recreationally trained runners VT1 was significantly different when measured via the SPXT and GXT (2.78 ± 0.5 vs. 2.99 ± 0.5 L.min-1, respectively) (t23 = -4.51, P < .01, ES = .42) whilst VT2 was also significantly different (3.10 ± 0.6 vs. 3.22 ± 0.6 L.min-1) (t21 = -2.35, P = .03, ES = .20). However, when calculated using different variables such as velocity, RPE, and HR, VT1 and VT2 were similar between protocols. This demonstrated that the SPXT can provide valid VT for runners.

The conclusion from this thesis is that the SPXT is a valid protocol for measuring V?O2max and can also be used to prescribe a programme of endurance training, and provide an accurate marker of VT.