Lactate recovery kinetics in response to high-intensity exercises

Abstract

Purpose

The aim of this study was to investigate lactate recovery kinetics after high-intensity exercises.

Methods

Six competitive middle-distance runners performed 500-, 1000-, and 1500-m trials at 90 % of their current maximal speed over 1500 m. Each event was followed by a passive recovery to obtain blood lactate recovery curves (BLRC). BLRC were fitted by the bi-exponential time function: La(t) = La(0) + A ₁(1–e ^−γ1t) + A ₂(1–e ^−γ2t), where La(0) is the blood lactate concentration at exercise completion, and γ ₁ and γ ₂ enlighten the lactate exchange ability between the previously active muscles and the blood and the overall lactate removal ability, respectively. Applications of the model provided parameters related to lactate release, removal and accumulation rates at exercise completion, and net amount of lactate released during recovery.

Results

The increase of running distance was accompanied by (1) a continuous decrease in γ ₁ (p < 0.05), (2) a primary decrease (p < 0.05) and then a stabilization of γ ₂, and (3) a constant increase in blood concentrations (p < 0.05) and whole body accumulation of lactate (p < 0.05). Estimated net lactate release, removal and accumulation rates at exercise completion, as well as the net amount of lactate released during recovery were not significantly altered by distance.

Conclusion

Alterations of lactate exchange and removal abilities have presumably been compensated by an increase in muscle-to-blood lactate gradient and blood lactate concentrations, respectively, so that estimated lactate release, removal and accumulation rates remained almost stable as distance increased.

Appendix

An application of the bi-compartmental model of lactate distribution space allows the prediction of the net lactate release rate (NLRR, mmol min⁻¹) during recovery using the following equation:

$${\text{NLRR}}\left( t \right) \, = \, (\gamma_{1} {-}d_{2} ) \times V_{S} \times A_{1} \times e^{{{-}\gamma_{1} t}} + \, (\gamma_{2} {-}d_{2} ) \times V_{S} \times A_{2} \times e^{{{-}\gamma_{2} t}} + \, \mu ,$$

(2)

where V _S is the volume of compartment S [i.e., 250 mL kg⁻¹ body mass; V _S  = V _TLS (volume of the total lactate distribution space) − V _M (lactate distribution volume of muscles previously involved in exercise)], µ is the net muscular release rate of lactate at t → ∞ and was set at 0.12 mmol min⁻¹ (Bret et al. 2003; Freund and Zouloumian 1981b; Maciejewski et al. 2013), and d ₂ is the efficiency of lactate utilization in compartment S. The application of the model gives realistic prediction when d ₂ is close to γ ₂. Therefore, to approximate NLRR, we set, as previously (Bret et al. 2003; Freund and Zouloumian 1981b; Maciejewski et al. 2013), d ₂ = γ ₂ − 0.005. The integral of Eq. (2) gives an estimation of the net amount of lactate released during recovery (NALR, mmol) from the previously active muscles to the blood (Bret et al. 2003). The maximal value (NALR_max) will be considered (Maciejewski et al. 2013).

Recently, Maciejewski et al. (2013) have developed a method to estimate the amount of lactate accumulated in the body at exercise completion (QLaA, mmol):

$${\text{QLaA }} = {\text{ QLaA at La}}_{\text{peak}} + {\text{ QLaR,}}$$

(3)

where QLaA at La_peak is the quantity of lactate accumulated at La_peak which is calculated as the following:

$${\text{QLaA at La}}_{\text{peak}} = {\text{ La}}_{\text{peak}} \times V_{\text{TLS}} ,$$

(4)

where La_peak represents the maximal blood lactate concentration during recovery, and V _TLS represents the volume of the total lactate distribution space (i.e., 500 mL kg⁻¹).

QLaR represents the amount of lactate removed from the end of exercise to La_peak, which is calculated as

$${\text{QLaR }} = \, [[{\text{La}}_{\text{peak}} + {\text{ La}}(0)]{ / 2}] \times \gamma_{ 2} \times t{\text{La}}_{\text{peak}} \times V_{\text{TLS}} ,$$

(5)

where tLa_peak is the time to reach the maximal lactate concentration during recovery. For more information about this method, we refer the reader to Maciejewski et al. (2013).

Lactate removal rate at the end of each exercise [LRR(0), mmol min⁻¹] was estimated from the following equation:

$${\text{LRR}}\left( 0 \right) \, = \gamma_{ 2} \times {\text{QLaA}} .$$

(6)

A calculation of the lactate accumulation rate (LAR, mmol min⁻¹) during each fraction of 500 m was derived from QLaA values according to the following equation:

$${\text{LAR }} = \, \Delta {\text{QLaA / }}t,$$

(7)

where ΔQLaA is the difference in QLaA between two distances and t is the time to complete 500 m. For the first 500 m, ΔQLaA = QLaA − (La_warm-up × V _TLS), where La_warm-up is the blood lactate concentration at the end of the warm-up.

As done in the past (Freund et al. 1986; Messonnier et al. 2001), a metabolic clearance rate of lactate during recovery (MCRR, mL kg⁻¹ min⁻¹) can be derived from γ ₂ values according to the following equation:

$${\text{MCR}}R = \gamma_{ 2} \times V_{\text{TLS}} .$$

(8)

A calculation of the lactate disappearance rate at exercise completion (R_d R(0), mg kg⁻¹ min⁻¹) can also be derived from Eq. (8) according to the following equation:

$${\text{R}}_{\text{d}} R\left( 0 \right) = {\text{MCR}}R\cdot\left( {{\text{QLaA / }}V_{\text{TLS}} } \right)\cdot\left( { 8 9 { / 1}000} \right).$$

(9)