Effect of New Zealand Blackcurrant Extract on Isometric Contraction-Induced Fatigue and Recovery: Potential Muscle-Fiber Specific Effects

Abstract

New Zealand blackcurrant (NZBC) extract has shown performance-enhancing effects during cycling, running and sport climbing. We examined effects of NZBC extract on (1) voluntary and twitch force of the quadriceps femoris muscles during repeated isometric contraction-induced fatigue, (2) twitch force during recovery and (3) muscle fiber-specific effects. Familiarized recreationally active males (n = 12, age: 24 ± 5 yrs; height: 180 ± 5 cm; body mass: 89 ± 11 kg) performed sixteen, 5-s voluntary maximal isometric contractions (iMVC) separated by 3-s rest. Twitch force was recorded before, during the 3-s rests and 5-min recovery. Supplementation consisted of 7-days intake of NZBC extract (600 mg∙day^-1 containing 210 mg anthocyanin) in a double-blind, randomized, placebo-controlled crossover design with a 14-days washout. NZBC extract allowed for greater force in the first quartile of the iMVCs. Twitch force at baseline was 12% higher with NZBC extract (p = 0.05). However, there was no effect of NZBC for twitch force during the 16-iMVCs and recovery. Based on the maximum post-activation potentiation during the placebo 16-iMVCs, four subjects were classified of having a predominant type I or II muscle fiber typology. In type II, NZBC extract provided a trend for increased MVC force (~14%) in the first quartile and for type I in the fourth quartile (~10%). In type I, NZBC extract seemed to have higher twitch forces during the fatiguing exercise protocol and recovery, indicating increased fatigue resistance. New Zealand blackcurrant extract affects force during repeated maximal isometric contractions. Future work on mechanisms by NZBC extract for muscle fiber-specific fatigue-induced force responses is warranted.

Keywords: anthocyanins; blackcurrant; muscle fatigue; muscle force; recovery; sports nutrition; twitch force.

Figure 1

(a) Voluntary maximum isometric force during the repeated 16 voluntary maximal isometric contractions (iMVCs). (b) Twitch forces during the repeated 16-iMVCs and recovery. For clarity, force data are presented as mean ± SEM. 1st, 2nd, 3rd and 4th represent the quartiles. * indicates a difference between conditions in the 1st quartile p = 0.047).

Figure 2

Voluntary maximum isometric force during the repeated 16-iMVCs for type I (a) and type II (b) fiber predominant typology. # indicates a trend for a difference between conditions in the 1st quartile (p = 0.064) and 4th quartile (p = 0.094).

Figure 3

Twitch force between the repeated 16-iMVCs and during recovery for type I (a) and type II (b) muscle fiber predominant typology. For clarity, data are presented as mean ± SEM.