Introduction
The graded exercise test (GXT) is a globally recognised test which offers valuable information on key aerobic parameters such as maximal oxygen uptake (
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\)), and can be used to prescribe training for both elite athletes, and recreational exercisers. Recently, a novel approach to the traditional GXT has been proposed, termed the self-paced
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\) test (SPV), which consists of 5 × 2 min stages where speed or power is freely adjusted by the participant based on rating of perceived exertion (RPE) (Mauger and Sculthorpe
2012; Borg
1982). The SPV has been applied across a wide range of exercise modalities and ergometry despite its relative infancy (Mauger and Sculthorpe
2012; Chidnok et al.
2013; Straub et al.
2014; Hogg et al.
2015; Jenkins et al.
2017b; Lim et al.
2016; Scheadler and Devor
2015).
The general consensus from published research to date suggests that the SPV provides comparable
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\) values to the GXT (Chidnok et al.
2013; Hogg et al.
2015; Lim et al.
2016; Scheadler and Devor
2015; Straub et al.
2014; Faulkner et al.
2015; Hanson et al.
2016), however, the methodological differences and contrasting populations used may make direct comparisons between studies challenging. Higher
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\) values have been observed within the SPV test (Mauger and Sculthorpe
2012; Jenkins et al.
2017a,
b; Astorino et al.
2015; Mauger et al.
2013), although all but one of these studies were cycling-based. However, the findings regarding differences in
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\) are less meaningful in terms of the utility of the test, with perhaps greater emphasis being placed on the practical advantages that the SPV has over the GXT. The problems associated with the GXT are well documented (Noakes
2008), such as the incremental fixed-intensity nature of the test, unknown test duration, and creating a test environment that is possibly unnatural and irrelevant for “real” sporting performance. It has, therefore, been put forward that the SPV may represent a paradigm shift in
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\) testing (Beltz et al.
2016), with self-paced protocols offering greater ecological validity due to the self-paced and closed-loop nature, whilst also circumventing the issue of estimating the ramp-rate and starting work rate for the researcher or practitioner (Poole and Jones
2017).
The GXT offers additional metrics in addition to the measurement of
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\), such as the velocity at
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\) (
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{{\text{2max}}}}\)) and the time in which
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{{\text{2max}}}}\) can be maintained (
Tmax). However, the identification of
Tmax requires an additional test which adds to the impracticality of the GXT. Nevertheless,
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\),
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{{\text{2max}}}}\) and
Tmax have been shown to be useful and viable parameters in running training and performance (Billat and Koralsztein
1996; Esfarjani and Laursen
2007; Manoel et al.
2017; Smith et al.
2003) and can be used to prescribe training and assess training adaptation. If similar metrics for training prescription could be acquired from the SPV, in a singular test, it would demonstrate utility over and above traditional GXT assessment of
\(\dot {V}{{\text{O}}_{{\text{2max}}}}\), especially as the SPV is an effective test for highly trained runners (Hogg et al.
2015; Scheadler and Devor
2015), and has good test–retest reliability (Jenkins et al.
2017a). In addition, the SPV has recently been validated as a field test (Lim et al.
2016), which increases its accessibility to a variety of athletes and coaches. Therefore, the ability to prescribe training from the SPV would enhance the value and utility of the test. As such, this study aimed to investigate whether training prescribed via novel metrics derived from the SPV could result in comparable improvements in key aerobic parameters as training formulated from traditional GXT variables.
Discussion
The primary finding of this study was that following a 6 weeks period of training, recreational runners' aerobic fitness and running performance was increased by a similar magnitude, regardless of whether SPV or GXT data were used to prescribe training. Specifically,
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) in the STND group improved by 4%, and by 6% in the S-P group. An improvement in
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) in the region of ~ 3% has previously been defined as a meaningful improvement in performance (Kirkeberg et al.
2010), as opposed to day-to-day variation. Previous literature has shown improvements in
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) by ~ 6% when training at 106%
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{2\hbox{max} }}\) (Franch et al.
1998) for similar training durations. However, in the aforementioned study the starting
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) for the participants were significantly lower than those reported in the current study, which may suggest a greater level of trainability for
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) (Swain and Franklin
2002) compared with the participants in the current study. Athletes of slightly higher training status’ than those in the current study achieved little to no improvements in
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) over 4–6 weeks of similar intensity training (Manoel et al.
2017; Smith et al.
2003; Denadai et al.
2006), but did show significant improvements in LT and 3–10 km running performance. Similar running programmes utilising interval training have also produced improvements in CS (Esfarjani and Laursen
2007). This is supported by the findings of the current study that in both STND and S-P, CS improved by 7 and 3%, respectively. For LT1 and LT2, STND improved by 5 and 3% and S-P improved by 7 and 8%.
An important finding of this study is that the novel training parameter extracted from the SPV, ‘
vRPE20’, is effective at prescribing running intensity for interval training. The
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{2\hbox{max} }}\) for the STND before and after training was 14.3 ± 0.9 vs. 15.2 ± 1.0 km h
− 1 compared to the S-P’s
vRPE
20 of 14.2 ± 1.9 vs. 15.7 ± 1.9 km h
− 1, respectively. It is likely that the
vRPE20 may reflect a speed between
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{2\hbox{max} }}\) and the maximal velocity achieved in a GXT (
Vmax).
Vmax has recently been shown to be as beneficial as
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{2\hbox{max} }}\) for exercise prescription (Manoel et al.
2017), and like
vRPE20 is simple to calculate. Moreover,
vRPE20 has been shown to be repeatable regardless of the pacing strategy adopted during this final stage (Hanson et al.
2017). This should be reason to encourage further investigation to assess the potential of
vRPE20 in training prescription and its suitability as a performance parameter.
As the aim of the study was to investigate whether SPV-derived training parameters could offer similar improvements in aerobic fitness compared to GXT prescribed training, it was important that training prescription was similar between groups in both intensity and duration. To calculate interval duration for the STND, 60%
Tmax was used. Setting interval duration at 60% of an individual’s
Tmax has been shown to produce significant improvements in aerobic parameters and 3–10 km running performance (Esfarjani and Laursen
2007; Manoel et al.
2017; Smith et al.
2003). In the study by Smith and colleagues (
2003), 60%
Tmax resulted in an average interval duration of 6 × 133.4 ± 4.1 s. This equated to ~ 13 min of high intensity effort per interval session. In the current study, 7 intervals at 120 s [which also matched the stage duration of the SPV] resulted in ~ 14 min of high intensity effort, ensuring it was comparable to the STND group (See Table
3). Durations of 2 min have been shown to elicit responses closer to
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) compared to shorter intervals (O’Brien et al.
2008). Longer interval work periods may have resulted in a greater
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) improvement (Esfarjani and Laursen
2007; O’Brien et al.
2008; Seiler and Sjursen
2002) but also significantly increased the interval duration. As a consequence, the mean prescribed training duration for each interval session over the 6 weeks training period was similar between groups (37 ± 8 vs. 38 ± 0 min for STND and S-P, respectively). Total training time over the 6-week period was also similar (804 ± 90 vs. 816 ± 0 min, for STND and S-P, respectively).
The similar
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) found between both protocols in this study is in line with previous research (Chidnok et al.
2013; Hogg et al.
2015; Lim et al.
2016; Scheadler and Devor
2015; Straub et al.
2014; Faulkner et al.
2015; Hanson et al.
2016). Even though test duration was significantly longer in the GXT, the test still fell within the recommended duration of 8–12 min (Yoon et al.
2007), and the
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{2\hbox{max} }}\) achieved was not significantly different between protocols. Interestingly, RER
max was significantly higher in the SPV, which has been observed in some (Mauger and Sculthorpe
2012; Hogg et al.
2015; Jenkins et al.
2017b), but not all previous SPV literature (Lim et al.
2016; Straub et al.
2014; Faulkner et al.
2015; Astorino et al.
2015). Consequently, no consensus on whether the SPV produces a higher RER
max can be currently drawn. However, the authors speculate that this potential difference in RER
max may be due to the higher peak velocities experienced in the SPV compared to the GXT, indicative of a greater anaerobic contribution towards the end of the test. This is supported by the recent work of Hanson and colleagues (
2017) who found, when comparing two SPV trials with different RPE20 pacing strategies, that RER
max was significantly greater in the SPV that adopted the more aggressive pacing strategy.
Table 3
Training prescription for a representative subject in both training groups
STND | Work: 6 × 167 s @ 15 km h− 1 Recovery: 5 × 334 s @ 8 km h− 1 | Work: 6 × 141 s @ 16 km h− 1 Recovery: 5 × 282 s @ 8 km h− 1 | 30 min @ 11.3 km h− 1 | 30 min @ 115 bpm |
S-P | Work: 7 × 120 s @ 15.6 km h− 1 Recovery: 6 × 240 s @ 8 km h− 1 | Work: 7 × 120 s @ 16.3 km h− 1 Recovery: 6 × 240 s @ 8 km h− 1 | 30 min @ RPE13 | 30 min @ 114 bpm |
Conclusions
The ability to prescribe training for recreationally active males and females via SPV-derived parameters offers coaches and athletes valuable alternatives to traditional methods. Prescribing training via the SPV is as effective but more time-economical. Specifically, the same level of improvement in key aerobic fitness parameters can be obtained when training is set via novel training parameters collected from a single 10 min SPV test compared to that achieved using a GXT and a mandatory additional test to acquire
Tmax data. This alone may make the SPV more attractive to athletes and coaches, however, recent research regarding a field based SPV (Lim et al.
2016) may emphasise this further. Whilst a field-based SPV has been shown to produce a valid directly measured
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\), future research should investigate whether
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) can be accurately estimated from the field based SPV. If so, athletes and coaches would then be able to utilize a single 10 min test on an athletics track, without expensive equipment, that would offer accurate
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\) estimation and data for effective training prescription. Therefore, the current findings demonstrate that training parameters derived from the SPV protocol can be used to prescribe effective running training that is similarly effective to training prescribed from GXT-derived parameters. Consequently, in the group that was prescribed training using SPV-derived parameters,
\(\dot {V}{{\text{O}}_{2\hbox{max} }}\), LTs and CS showed similar improvements compared to runners who were prescribed training via
\({}_{{\text{v}}}\dot {V}{{\text{O}}_{2\hbox{max} }}\) and LT zones
, with training durations and intensities suitably similar between groups throughout training.