Six-minute rowing test: a practical tool for training prescription, from ventilatory thresholds and power outputs, in amateur male rowers

Experimental approach to the problem

An observational design with an associative and cross-sectional strategy was used to relate the outcomes of VT1, VT2, and VO_2max obtained in the IT to the outcomes of the 6-min_RT (Ato, López & Benavente, 2013) (Fig. 1). All study participants attended the laboratory for three days at 72-hour intervals. Also, participants did not exercise between assessment days. The time between races ensures the rowers’ physical recovery (American College of Sports Medicine, 2013). During the first visit, participants signed the informed consent form and were evaluated with basic anthropometry; on the second day, they performed the IT, and on the third day, the 6-min_RT (Fig. 1A).

Participants

Sixteen male amateur rowers participated voluntarily in this study (age 20.8 ± 2.2 years [range: 18–27], body mass 79.7 ± 7.6 kg [range: 68.2–103.6], stature 176.2 ± 5.1 cm [range: 169–186], BMI 25.7 ± 2.2 kg/m² [range: 22.5–31.3], body fat percentage 12.9 ± 2.9% [range: 7.1–19.9], VO_2max 46.32 ± 4.09 mLO₂ kg⁻¹ min⁻¹ [range: 36.48–52.66], and theoretical maximum HR (Tanaka, Monahan & Seals, 2001) 191.5 ± 1.9 [range: 187.1–193.4]. The inclusion criteria were previously described in Huerta Ojeda et al. (2022b). Specifically, the main inclusion criterion was the VO_2max assessed in the IT. This initial evaluation made it possible to verify the fitness level of the male amateur rowers. In this regard, all participants in the study presented a VO_2max between 33–55 mLO₂ kg⁻¹ min⁻¹. Also, it was found that the rowers trained between 3–6 h per week. All these antecedents allowed defining the participants as amateur rowers, also classified as ‘Recreationally Active’ (McKay et al., 2022). In contrast, rowers who did not reach the VO_2max in the IT, according to the criteria described in the literature (Howley, Bassett & Welch, 1995; American College of Sports Medicine, 2013), or could not finish the 6 min of the 6-min_RT were eliminated during the study. Statistical software (G*Power, v3.1.9.7; Heinrich-Heine-Universität, Germany) was used to calculate the sample (Faul, 2020). The combination of tests used in the statistical software to calculate the sample size was as follows: (a) t-test, (b) Correlation: Point biserial model, and (c) A priori: Compute required size –given α, power, and effect size. Tests considered two tails, slope H1 = 0.61, α-error < 0.05, and a desired power (1 −β error) = 0.8. The total sample size was 16 participants. All participants were informed of the study’s objective and the possible experiment risks. Before applying the protocols, all amateur rowers signed the informed consent form in person. The study and the informed consent were approved by the Scientific Ethical Committee of the Universidad Mayor, Santiago, Chile (registration number: 197_2020) and developed under the ethical standards for exercise and sports sciences (Harriss, Macsween & Atkinson, 2019).

Anthropometric measurements

For the characterization of the sample, body mass, stature, body mass index (BMI), and body fat percentage were evaluated. According to the international anthropometric assessment protocol, weight (kg) was assessed with a digital weight (TANITA, model InnerScan BC-554^®, Tokyo, Japan). Height (m) was assessed with a stadiometer (SECA, model 700^®; SECA, Hamburg, Germany), respecting the Frankfort plane and maximum inspiration. This ensured that the participants were evaluated in a euhydrated condition. The body fat percentage was assessed using an impedance meter (Tanita Inner Scan, BC-554^® digital scale; Tanita, Tokyo, Japan).

Snack

The snack prevents athletes from starting evaluations with a low blood glucose level (Ojeda et al., 2019). Este snack ensured a blood glucose level between 100–120 mg/dl, considered optimal before exercise (DeMarco et al., 1999). It was a carbohydrate load before the IT and 6-min_RT. All participants were available two hours before the tests in a fasting condition. The snack consisted of 2 g of rapidly absorbed carbohydrates per kg body mass, including fruit, fruit juice, bread, and jam (Fig. 1B).

Standardized warm-up

The warm-up consisted of 10 min on a bicycle (Airbike Xebex^® resistance; ABMG-3 Xebex Fitness). The warm-up intensity was 60–70% of the theoretical maximum HR, calculated through the formula: 208-(0.7*age) (Tanaka, Monahan & Seals, 2001). Five minutes of upper and lower extremity ballistic movements were then included (upper extremity: 1 × 10 shoulder adductions, abductions, flexion, and extension; lower extremity: 1 × 10 hip adductions, abductions, flexion and extension, and knee and 1 ×10 ankle flexion and extension, right and left respectively). After, athletes rowed for five minutes between 60–70% of the theoretical maximum HR (Tanaka, Monahan & Seals, 2001), and finally, there was a 10-minute rest (this time was used to install the mask and HR sensors) (Fig. 1B).

Incremental test

The objective and characteristics of the test were previously described in Huerta Ojeda et al. (2022b). Specifically, this test aims to progressively reach VO_2max and its equivalent PO or MAP. All ventilatory parameters were evaluated during IT with an automatic gas analyzer system (model Quark CPET; Cosmed, Rome, Italy). Before IT, the analyzer was calibrated strictly according to the manufacturer’s recommendations. The data were processed through a laptop computer, which calculated the results using software developed by the manufacturer. The IT was performed on a remoergometer (Concept2 Model D, PM5 monitor) using a drag factor of 117–119. The IT started with 100 watts (W) and was increased by 35 W every minute until exhaustion or the impossibility of maintaining the requested power (Mekhdieva, Zakharova & Timokhina, 2019). Two experienced investigators monitored the test. VO_2max was determined based on the following criteria (Howley, Bassett & Welch, 1995; American College of Sports Medicine, 2013): (i) when setting plateau, display a variation < 150 mlO₂ min⁻¹, (ii) a respiratory exchange ratio (RER) ≥ 1.1, and/or (iii) Theoretical maximum HR ≥ 90%. VO_2max was recorded with absolute (LO₂ min⁻¹) and relative values (mlO₂ kg⁻¹ min⁻¹). In addition, pulmonary ventilation was recorded (VE) at VO_2max (L min⁻¹) and RER at VO_2max (VCO₂/VO₂) (Howley, Bassett & Welch, 1995). VT1 and VT2 were identified according to the following criteria (Davis, 1985; Lucía et al., 2000; Cerezuela-Espejo et al., 2018): VT1, the intensity causing the first increase in ventilatory oxygen equivalent (VE/VO₂) without a simultaneous increase in ventilatory carbon dioxide equivalent (VE/VCO₂); VT2, the intensity that causes an increase in VE/VO₂ and VE/VCO₂ and a decrease of CO2 at the end of exhalation (PETCO₂). All the mechanical parameters performed in the rowing meter were recorded during IT. Also, the HR was recorded during the development of the IT through an HR monitor (model H10^®, Polar, Kempele, Finland). During IT, ventilatory parameters were recorded breath by breath, while mechanical parameters and HR were recorded from stroke to stroke. Subsequently, all data were averaged and synchronized at 15 s intervals. At the end of the IT, to evaluate the rating of perceived exertion (RPE) of the participants, the modified Borg scale was used (1–10) (Borg, 1990).

Six-minute rowing test

The purpose of this test is that the participant rows the longest distance possible for 6 min on an ergometer rowing machine. From a ventilatory and mechanical point of view, the 6-min_RT is a maximal test that allows the establishment of the MAP in amateur rowers (Huerta Ojeda et al., 2022b). The final 6-min_RT distance is recorded in meters (m). The 6-min_RT was performed on a rowing machine (Concept2 Model D, monitor) using a drag factor of 117–119. Two experienced investigators monitored the test. During the 6-min_RT, all ventilatory parameters were evaluated with the same automatic gas analyzer system used in the IT (model Quark CPET; Cosmed, Rome, Italy). During the 6-min_RT, ventilatory parameters were recorded breath-by-breath and then averaged at 15-s intervals. In this study, the slow and fast VO₂ components were determined by visual inspection of each curve, specifically from the moment a plateau was generated in the VO₂ curve until the end of the 6-min_RT (Billat et al., 1998; Womarck et al., 2000). For the statistical analysis, the ventilatory parameters correspond to the slow component of the VO₂ (VO_2max abs, VO_2max rel, VE, and RER). During the 6-min_RT, all mechanical parameters performed on the rowing meter were recorded. Also, HR was recorded during the 6-min_RT through an HR monitor (model H10^®; Polar). During the 6-min_RT, mechanical parameters and HR were recorded from stroke to stroke. Subsequently, all data were averaged and synchronized in a single 360 s interval. At the end of the 6-min_RT, to evaluate the rating of perceived exertion (RPE) of the participants, we used the modified Borg scale (1–10) (Borg, 1990).

Statistical analyses

Data were collected as described in Huerta Ojeda et al. (2022b). Specifically, ventilatory, mechanical, and HR parameters were sorted for all the tests on a spreadsheet designed for the study. Descriptive data are presented as means and standard deviation (SD). The Shapiro–Wilk test confirmed the normal distribution of the data (p > 0.05). Pearson’s test calculated the correlation between the VT1, VT2, and VO_2max outcomes obtained in the IT with the 6-min_RT outcomes (r and r²) (Hopkins et al., 2009). The criteria for interpreting the strength of the r coefficients were as follows: trivial (<0.1), small (0.1–0.3), moderate (0.3–0.5), high (0.5–0.7), very high (0.7–0.9), or practically perfect (>0.9). A 95% confidence interval was used for all statistical analyses, and the significance level was p < 0.05. All statistical analyses were performed with Prism version 7.00 for Windows^® software.

VTs and VO_2max through IT

When analyzing VT1, it was observed that male amateur rowers reached a VO₂ equivalent to 55% of VO_2max. From the ventilatory perspective, the percentage value of VO_2max reached by the present study’s participants is lower than existing theoretical reference parameters (60–65% of VO_2max) (López Chicharro, Vicente Campos & Cancino López, 2013). Finally, the low percentage of VT1 observed may be associated with the low aerobic capacity of the amateur rowers in the study (Billat, 1996). This situation would limit both the oxidative capacity of muscle fibers and the aerobic contribution to energy metabolism (Mickelson & Hagerman, 1982). However, this point needs to be studied further. Another essential variable to analyze to establish VT1 is the RER (Davis, 1985; Lucía et al., 2000; Cerezuela-Espejo et al., 2018). In this sense, the value of RER observed in the present study for VT1 (0.87 ± 0.08 VCO₂/VO₂) is coincident with the RER value reported by other research in rowers (0.89 ± 0.018 VCO₂/VO₂) (Cerda-Kohler et al., 2022). However, considering that the present study proposes to provide tools for the field without gas analysis, it is important to analyze some of the mechanical and HR parameters achieved in VT1. In fact, in this specific area, the pace every 500 m was 144.4 ± 6.1 s (62% of pace in VO_2max), while HR was equivalent to 132.9 ± 5.5 bpm (69% of HR_max). These results indicate that VT1 corresponds to 55 of the mechanical outcomes and 65–70% of the HR.

When analyzing VT2, it was observed that the participants reached a VO₂ equivalent to 80% of VO_2max. From the ventilatory perspective, the percentage value of VO_2max reached by the rowers in this study is within the theoretical reference parameters (80–85% of VO_2max) (López Chicharro, Vicente Campos & Cancino López, 2013). As in VT1, it is important to observe the RER achieved in VT2 (Davis, 1985; Lucía et al., 2000; Cerezuela-Espejo et al., 2018). In this context, the value of RER observed in the present study for VT2 is also coincident with the RER value reported by other research in rowers (Cerda-Kohler et al., 2022). In this sense, it is important to observe some of the mechanical and HR parameters achieved in VT2 to use them for training prescription. In this specific zone, the pace every 500 m was 118.1 ± 4.9 s (85% of pace in VO_2max), while the HR was equivalent to 162.7 ± 10.6 bpm (85% of HR_max). In this sense, the contribution of the present study is associated with the determination of VT. Indeed, after applying the 6-min_RT, it is possible to obtain HR and mechanical parameter values corresponding with VT2 for amateur rowers (80%). Thus, HR and mechanical parameters facilitate exercise prescription (Cerezuela-Espejo et al., 2018). The 6-minRT thus becomes a practical and easily accessible tool for monitoring and evaluating amateur rowers.

The VO_2max achieved by amateur rowers classifies them as ‘good’ (Herdy & Caixeta, 2016). In addition, both the RER achieved the HR at the same intensity, indicating that the male amateur rowers reached the VO_2max (Davis, 1985; Lucía et al., 2000; Cerezuela-Espejo et al., 2018). As in the VTs, the present study proposes providing tools for the field without gas analysis. Therefore, it is important to analyze some of the mechanical and HR parameters achieved in VO_2max. At this intensity, the pace every 500 m was 100.3 ± 3.4 s, while the HR was equivalent to 191.2 ± 6.8 bpm.

6-min_RT and ventilatory thresholds

Previous studies have established that the 6-min_RT is a valid and reliable test for determining MAP in male amateur rowers (Huerta Ojeda et al., 2022b). Likewise, the present study determined that male amateur rowers reach VT1 and VT2 at 55% and 80% of VO_2max, respectively. This background, together with the high correlations between IT outcomes and the 6-min_RT (r > 0.6), allows inferring that the distance, PO, and HR achieved in the 6-min_RT should be in good agreement with the VTs and VO_2max of the IT. That is, 55% of the 6-minRT would correspond to VT1, 80% to VT2, and 100% to MAP. Therefore, training loads should be prescribed ≤60% (VT1) if the purpose of training is to generate intramuscular and metabolic adaptations (such as increased expression of type I myosin heavy chains, reduced work HR—sympathoadrenal adaptation—and/or optimization of the fatty acid oxidative pathway) (López Chicharro, Vicente Campos & Cancino López, 2013). Based on the results of the male amateur rowers in the present study, training loads should be prescribed between 55–80% (aerobic-anaerobic transition zone) to (a) increase the oxidative muscle capacity of type IIa fibers—especially the oxidation of intramuscular fats—, (b) increase the possibility of sustaining prolonged exercise with a lactate level close to 2–3 mmol-L-1, and (c) increase the buffering capacity and maintenance of musculoskeletal acid–base balance (López Chicharro, Vicente Campos & Cancino López, 2013). However, to achieve the physiological adaptations described above, it is suggested to train close to, but not over 80%. Finally, if the training goal is to increase muscle shortening capacity (which would lead to an increase in rowing pace), adapt the sarcoplasmic reticulum for increased calcium release, increase glycolytic activation, and enhance lactate transport across cell membranes, training loads should be prescribed 80% (López Chicharro, Vicente Campos & Cancino López, 2013). In this context, an Excel spreadsheet is available to automatically calculate the PO and stroke rate by zones and the pace every 500 m from the result in the 6-min_RT (see practical applications).

Some responses and adaptations generated by the prescribed loads in the different training zones have been described. However, it is essential to mention that each athlete’s physiological responses and adaptations to a stimulus are different; therefore, the training prescription should consider the level of training, sex, and years of experience, among other factors (Scott et al., 2016).

Limitations

The absence of females in the study limits the conclusions only to study participants and amateur male rowers. The lack of descriptive information on field attainment of VT1 in rowers made it challenging to compare our results.

Practical applications

Considering that the 6-min_RT allows MAP to be obtained and that, in the present study, the thresholds for this field test were determined (55% for VT1 and 80% for VT2), only the creation of tools to facilitate its use in training prescription are missing. For this purpose, a spreadsheet that automatically calculates the pace and PO times for each intensity and training zones based on the results of the 6-min _RT is provided in this study. For the correct use of the spreadsheet, together with the personal data and evaluation date, the total distance and the average power achieved in the 6-min_RT must be included. After this, as many sheets as necessary can be created. To facilitate the spreadsheet, 55% for VT1 and 80% for VT2 (thresholds obtained by the male amateur rowers in this study) are highlighted in yellow. The spreadsheet also allows us to project performance over 2,000 m (green cell). This projection was obtained through a linear regression performed in previous studies on male amateur rowers (Huerta Ojeda et al., 2022a). Finally, in black, the MAP for each rowing pace is highlighted (https://doi.org/10.6084/m9.figshare.22190026).