**3.3 Severe intensity domain**

162 Bioenergetics

involvement, called "aerobic inertia" (τ), understood as a temporary delay in the response of VO2, caused by dissociation of O2 absorbed in lungs and used especially by skeletal muscle. The use of CV in swimming training is suggested since 1966 (Ettema 1966). Studies by

Some authors (Gaesser et al. 1996; Greco et al. 2008) suggest a range of intensities of three domains (sometimes referred as training zones) and others (Dekerle & Pelayo 2011) a scale of five domains and their physiological effects. According to Table 1, exercise can be conducted in three different intensity domains, resulting in very distinctive physiological

There is no variable metabolic stabilization;

increase of protons concentration [H+]; VO2 increases toward the maximum.

[La] stabilizes at high values of concentration

perform the exercise for a longer period.

Table 1. Intensity domains and their physiological effects (Gaesser et al. 1996; Greco et al.

[La] stabilizes quickly and can be maintained almost similar to resting levels. Similarly, VO2 shows a quick set (1-3 min) before stabilization, and the individual can maintain the intensity for hours without exhaustion. The main explanation for the "end" of the exercise refers to substrate depletion (muscle and liver glycogen), changes related to hydration and electrolytes or problems related to the process of thermoregulation (Greco et al. 2008).

Production and removal rates of lactate levels are high due to a high metabolic demand. Consequently, [La] tends to stabilize at higher concentrations when compared to exercise at moderate intensity. Moreover, the efficiency of the specific motor gesture seems to be smaller, generating higher VO2 values than the linear relationship between VO2 and exercise intensity that characterizes the Moderate intensity domain (development of a slow

High VO2 values (development of a slow component);

The efficiency appears to be lower;

Accumulation and increase of lactate / pyruvate relationship and

It is still possible to maintain a stable physiological state and

The individual can maintain this intensity for hours without

researchers about its use continue to be published (Dekerle & Pelayo 2011).

effects in each of these domains (Gaesser et al. 1996; Greco et al. 2008).

**domains Effects** 

 [La] stabilizes quickly; VO2 has a quick adjustment;

exhaustion.

**3. Intensity domains (training zones)** 

**Intensity** 

**SEVERE** 

**HEAVY** 

**MODERATE** 

**3.1 Moderate intensity domain** 

**3.2 Heavy intensity domain** 

2008)

There is no stabilization in metabolic variables. Specifically, the rate of lactate production is greater than the rate of removal, with a consequent increase in the accumulation and the relationship between lactate and pyruvate and the concentration of protons ([H+]) (Greco et al. 2008). At the same time, VO2 increases towards to its maximum (VO2max) and the amplitude of the slow component is much higher than those that characterize the heavy intensity exercise (Xu & Rhodes 1999). This reduces exercise tolerance, with *tlim* related to the cellular level of disturbance (metabolites production and removal rates), caused by high demand of muscle adenosine 3-phosphate (ATP) (Greco et al. 2008).

## **3.4 Scale of five intensity domains proposed by Dekerle & Pelayo (2011)**

Dekerle & Pelayo (2011) propose a scale of five domains and their physiological effects. On this scale, lactate threshold (LT), MLSS and CV2par can be understood as boundaries that demarcate some intensity domains. Figure 1 shows the five intensity domains proposed by Dekerle & Pelayo (2011), in which the behavior of [La] and VO2 is illustrated in each domain.

Fig. 1. Intensity domains (adapted from Dekerle & Pelayo 2011) and the response of each to [La] and VO2 kinetics during exercise in different SS.

Bioenergetics Applied to Swimming: An Ecological Method to Monitor and Prescribe Training 165

In addition, the physiological responses to swimming at intensities equal to or above the MLSS are still unclear, since it is not certain that VO2max is reached. Thus, it is justifiable to establish at least one domain between the MLSS and CV2par: the "very heavy intensity domain". Thus, exercise performed in this domain (very heavy) suggests an increase in [La] and the occurrence of the VO2 slow component, but without reaching VO2max in the end of the exercise (Dekerle et al. 2010). VO2max would only be achieved if the exercise was conducted in intensity above CV2par and continued until exhaustion (featuring the severe domain). Thus, CV2par represents the boundary between very heavy and severe intensity domain. However, Dekerle & Pelayo (2011) suggest that more experiments are needed in these models of training zones. As a result, coaches and swimmers will be able to use them

Based on the information presented, it is believed that the model of five intensity domains proposed by Dekerle & Pelayo (2011) best describes the physiological responses to exercise

PC was used initially to determine exercise intensity that could be theoretically maintained for a long period of time without exhaustion (Monod & Scherrer 1965). CP (or CV in running or swimming) proved to be valid for aerobic capacity prediction (Dekerle et al. 2005a) and sensitive to physiological changes from aerobic training programs (Jenkins & Quigley, 1991). CP or CV determined by two-parameter model (CP2par or CV2par) represents the lower boundary t of the severe intensity domain (Poole et al. 1990; Hill & Ferguson 1999). Poole et al. (1990) found that when subjects performed exercise intensity on CP2par, VO2 stabilized around 75%VO2max. In addition, studies have investigated the hyperbolic relationship between power and time to achieve VO2max. The results also suggest that this relationship is the lower boundary of the severe intensity domain, or CP2par (or CV2par) (Hill & Smith 1999; Hill & Ferguson 1999). Thus, CV2par can determine the exercise intensity

The physiological meaning of ADC2par is still subject of many studies (Moritani et al. 1981; Green et al. 1994; Miura et al. 2000; Heubert et al. 2005). Evidence trying to suggest the ADC2par anaerobic nature was observed in cyclists (Green et al. 1994). Also in cyclists, Heubert et al. (2005) found a decrease of 60 to 70% in ADC2par values as a result of a 7 s maximal effort performed before a protocol of four exercises at constant intensity (95, 100, 110 and 115%VO2max) and to determine the ADC2par and CP2par. CP2par values did not change. Moritani et al. (1981) also found no differences in ADC2par values in response to ischemia, hypoxia and hyperoxia. In relation to prior depletion of glycogen, Miura et al. (2000) found a decrease in ADC2par values (in cycle ergometer). Jenkins & Quigley (1993) found an increase in ADC2par values in response to high-intensity training in untrained individuals, but the CP2par values did not change. ADC2par values also showed increases in response to creatine supplementation (Miura et al. 1999) and demonstrated good correlation with predominantly anaerobic exercises (Vandewalle et al. 1989; Jenkins & Quigley 1991; Hill 1993; Dekerle et al.

with a greater degree of reliability.

**4. Physiological meaning of each parameter** 

equivalent to the lower boundary of the severe intensity domain.

**4.1.2 Anaerobic distance capacity (ADC2par)** 

in different intensities.

2005b).

**4.1 Two-parameter model 4.1.1 Critical Speed (CV2par)** 

Each of the five intensity domains (Dekerle & Pelayo, 2011) is characterized by acute specific physiological responses. Dekerle & Pelayo (2011) establish the lactate threshold (LT) as the boundary between moderate and heavy domain. The LT is defined as the first increase in lactate response to an incremental test (Wasserman et al. 1990).

#### **3.4.1 Heavy intensity domain**

The exercise is performed in intensity very close to the LT, but a little higher, which causes a small increase in [La] (no more than 1 mmol·l-1) in the first minutes, with subsequent stabilization close to resting levels (≈ 2.1 mmol·l-1). The maximum exercise intensity at which [La] stabilization occurs is defined as maximal lactate steady state (MLSS, ≈ 3-5 mmol·l-1) (Beneke, 1995). The MLSS is the heavy intensity domain upper limit (Barstow 1994). The intensity corresponding to LT can be maintained for a very long period (e.g. aquatic marathons) and occurs at a slower speed when compared to MLSS (*tlim* ≈ 60 min). MLSS is located in the smaller SS than CV2par (*tlim* ≈ 14.3 to 39.4 min). Importantly, for being difficult to detect the MLSS through the curve obtained in [La] and SS, and also to avoid any misinterpretation, the term "anaerobic threshold" should not be associated to the MLSS. Swimming in a very low SS is a difficult task (<0.4 to 0.5 ms-1 or 50-60% of V400 -average speed of 400 m front *crawl* in maximal effort). Thus, the lowest speed that can be adopted by swimmers using a good technique, it is almost equal to LT (Dekerle & Pelayo 2011).

#### **3.4.2 Severe intensity domain**

In SS above the MLSS (heavy intensity domain upper limit) there is an increase in [La], HR and VO2 (occurrence of the slow component). Initially, it was suggested that the increase in VO2 in these intensities reach the maximum (VO2max) before exhaustion, which characterizes the severe intensity domain). This statement is controversial and difficult to investigate because of the low reliability of time to exhaustion obtained in constant intensity tests (variability of *tlim*) (Hinckson & Hopkins, 2005). The SS equivalent to the Severe intensity domain includes performances of approximately 2 to 60 minutes (VO2max reaching the end of the exercise) with the performance of 400 m in front *crawl*, the maximum aerobic speed (MAS) and CV2par lying within that domain (Lavoie & Montpetit et al 1981; Lavoie et al. 1983; Lavoie & Leone 1988; Rodrigues 2000; Pelayo et al. 2007; Billat et al. 2000; Dekerle et al. 2010).

#### **3.4.3 Extreme intensity domain**

This domain includes performances of very short duration (< 2 min). Due to the limited response of VO2, VO2max is not reached during exercise, although the task is performed to exhaustion.

#### **3.4.4 Very heavy intensity domain**

Dekerle & Pelayo (2011) suggest the subdivision of Heavy intensity domain. According to these authors, the range of effort associated to this area is wide (performances of ≈ 2 to 60 min) and associated with many chronic responses to training, i.e., the physiological adaptations of a training period in SS near the MLSS are different from the training adaptations induced by a training period in MAS or above.

In addition, the physiological responses to swimming at intensities equal to or above the MLSS are still unclear, since it is not certain that VO2max is reached. Thus, it is justifiable to establish at least one domain between the MLSS and CV2par: the "very heavy intensity domain". Thus, exercise performed in this domain (very heavy) suggests an increase in [La] and the occurrence of the VO2 slow component, but without reaching VO2max in the end of the exercise (Dekerle et al. 2010). VO2max would only be achieved if the exercise was conducted in intensity above CV2par and continued until exhaustion (featuring the severe domain). Thus, CV2par represents the boundary between very heavy and severe intensity domain. However, Dekerle & Pelayo (2011) suggest that more experiments are needed in these models of training zones. As a result, coaches and swimmers will be able to use them with a greater degree of reliability.

Based on the information presented, it is believed that the model of five intensity domains proposed by Dekerle & Pelayo (2011) best describes the physiological responses to exercise in different intensities.
