Introduction:
Judo requires highly technical and tactical skills with physiological response optimization to succeed.

Aim of the study:
The present study aims to investigate an association between a rating of perceived exertion (RPE), a heart rate (HR), and a blood lactate concentration [La–] along with a grip strength (GS) deterioration in successive judo simulations (randori).

Material and methods:
Ten male judokas performed six successive fights (randori), of 5-minute each, with 5-minute rests. The HR, [La–], GS, and grip activation time (GAT) were recorded with a standard procedure at various time points (resting – T0 and after each bout T1-T6).

Results:
The HR and [La–] showed significant (p < 0.001) differences when compared among T1-T6, including T0, but a variation in the HR (ΔHR) and a variation in the lactate concentration (Δ[La–]) reported no significant difference after a post-simulation data comparison. The GS (for both dominant and non-dominant hand) reported significant differences among post-simulation GS measurements, including T0. The GAT was negatively and significantly (p < 0.01) correlated with GS-right (r = –0.397) and GS-left (r = –0.440). Similarly, the RPE was positively correlated with the ΔHR, Δ[La–], HR, and [La–]. Whereas the GS (for both hands) was negatively (p < 0.05) correlated with the Δ[La–] and [La–]. Finally, the ΔHR was positively (p < 0.01) correlated with the Δ[La–] and [La–].

Conclusions:
Judo simulations involve high-intensity exercises, leading to a maximum average frequency RPE of 7-9 with an HR of 192-193 beats·min-1 (90-95% HRmax) and 9.79-15.41 mmol·L-1 of peak [La–]. The RPE was positively (significantly) correlated with the ΔHR, Δ[La–], HR, and [La–]. Whereas the GAT was negatively (significantly) correlated with the GS-right and GS-left.