AbstractLactate produced during exercise is no longer thought of as a waste product and it is now understood it plays an important role in exercise metabolism.
Exercise intensity during invasion sports elicits a mean heart rate of approximately 85% HRmax which equates to 80% V̇O2max and blood lactate concentration greater than 4mmol·l-1. It is likely that an athlete’s ability to metabolise this lactate and maintain a lactate balance is a key determining factor in match performance. Supplemented lactate is utilised more rapidly and to a greater extent than glucose and helps maintain performance level for the repeated high intensity actions required throughout invasion sport match play.
Study 1 examined the effect of supplementing calcium lactate during simulated rugby union match play to determine whether sprint speed and intermittent sprint performance could be improved. Ten recreationally active participants were recruited for part one of the study to determine the rate at which orally consumed lactate solution appears in the blood. For part two of the study, seven amateur rugby union players (age: 25 ± 5 years, weight: 84 ± 6kg, and height: 180 ± 4cm) underwent the BURST under three conditions to compare water, glucose, and lactate. Sprint performance was measured through 17 x 15m maximal sprints over the course of the BURST. An increase in blood lactate concentration ([La-]b) was evident within 10 minutes of ingestion and it was significantly (p ≤ 0.05) elevated from 20 to 60 minutes post ingestion. There was no change in blood glucose concentration throughout the testing period. There was no significant (p > 0.05) difference in sprint time between conditions at any performance test, with total sprint time per block, per half, and across the full BURST protocol also showing no difference. There was no significant difference in decrement of sprint performance between the first and second (p = 0.69), or third and fourth (p = 0.13) exercise blocks, or between the first and second halves (p = 0.59). There was a significant difference in peak heart rate between condition in both the first (C = 179 ± 4, L = 172 ± 6, G = 179 ± 9; p = 0.04) and second (C= 178 ± 3 L = 170 ± 7, G = 176 ± 6; p = 0.03) halves of simulated match play. There was no significant difference in respiratory rate between conditions in either the first (C = 44 ± 8, L = 38 ± 6, G = 47 ± 11; p =0.16) or second (C = 42 ± 17, L = 36 ± 6, G = 40 ± 19; p = 0.68) halves. Supplementation of 1% Wt/vol calcium lactate solution did not enhance sprint speed or significantly reduce the drop in sprint performance seen throughout a match. There was a trend for the decrement in performance to be less in the lactate condition and therefore, the use of calcium lactate may be recommended prior to rugby matches as an ergogenic aid to sustain sprint performance although any benefit is likely to be marginal.
Study 2 investigated the effect of sprint interval training on soccer specific performance indices and lactate kinetics. In youth soccer, 23% of the distance covered happens at speeds above maximal lactate steady state (MLSS) which suggests lactate kinetics may be important to soccer performance. Thirteen elite soccer academy players (age 15 ± 0.5y) underwent baseline testing (Wingate anaerobic Test (WAnT) with blood lactate measurements, incremental V̇O2peak and time to exhaustion test, 0-10m and 10-20m sprint performance, repeated 20m sprint performance, and vertical jump performance) before being allocated to control or SIT group. The control group maintained training whilst the SIT group carried out twice-weekly all-out effort cycle sprints consisting of 6 x 10s sprint with 80s recovery. Training elicited significant improvements in V̇O2peak (pre: 54.89 ± 3.09ml· kg−1·min-1 post: 60.81 ± 5.73ml· kg−1·min-1; p = 0.001), TTE (pre: 655 ± 54s post: 688 ± 55s; p=0.001), 10 - 20m sprint time (pre: 1.29 ± 0.04s post: 1.25 ± .04s; p=0.02), and peak power during WAnT (pre: 12.4 ± 1.3 W.kg-1 post: 15.3 ± 0.7W.kg-1; p=0.003) which were not seen in the control group. The changes in performance were significantly correlated to changes in lactate kinetics (time to exhaustion: r=0.77, p = 0.04). Cycle-based SIT is an effective training paradigm for elite youth soccer players and the improvements in match specific fitness indices are associated with changes in lactate kinetics. These increased levels of lactate utilisation may facilitate a greater ergogenic benefit from supplemented lactate solution further enhancing its ability to mitigate the decline in sprint performance seen throughout invasion sport match play.
Study 3 examined the effect of calcium lactate supplementation of laboratory-based performance tests specific to field hockey. It also sought to determine whether lactate kinetic altering sprint interval training would enhance any ergogenic effect of the supplementation. Invasion sports such as field hockey require players to perform multiple repetitions of maximal effort sprints, with the volume and intensity of these playing a critical role in determining level of match performance. The drop in sprint performance over the duration of match play is linked to reduced substrate availability leading to fatigue, and there a various ergogenic aids used to mitigate this. One such supplement is lactate which has been shown to possibly maintain high-intensity exercise performance with the effect being amplified as cardiorespiratory fitness increases. Eleven amateur female field hockey players underwent baseline testing for CP, V̇O2peak, TTE, PP and RSA both with and without supplemented calcium lactate solution. This was followed by a control period where normal training and match play were maintained. Testing was then repeated before and after carrying out twice-weekly all-out effort cycle sprints consisting of 6 × 10 s sprint with 80 s recovery. There were no differences in performance between either condition at the baseline testing or following the control period (p > 0.05).There was no change in any performance indicator following three-week control period (p > 0.05). Training elicited significant improvements in CP (Pre 2: 210 ± 2W; Post: 222 ± 25W, p = 0.01), V̇O2peak (Pre 2: 40.27 ± 6.04 ml· kg−1·min-1; Post: 44.52 ± 4.11 ml· kg−1·min-1, p = 0.02), and TTE (Pre 2: 613 ± 99s; Post: 677 ± 118s, p = 0.01). There were no changes in either power at LT (Pre 2: 118 ± 21W; Post: 118 ± 18W, p = 1.00), or [La-]b at LT (Pre 2: 3.15 ± 0.64 mmol·l-1; Post: 2.91 ± 0.47 mmol·l-1, p = 0.17). With the exception of TTE (p = 0.003) which saw a significant detrimental effect of lactate supplementation, there were no differences between condition during post-training testing (p > 0.05). It is evident performing cycling-based SIT training twice-weekly in addition to the regular field hockey training sessions can help players develop aerobic and anaerobic capacity in a short period of time. It would appear supplementation of a 2% calcium lactate solution offers no ergogenic benefit for short-duration performance tests and may in fact have a detrimental effect on endurance capacity.
Together, these studies show that supplementation of calcium lactate solution is not an effective method to enhance physical performance during aerobic and anaerobic performance tests. It may provide a small mitigation to the decline in sprint performance seen over the course of invasion sport match play. Therefore, the use of calcium lactate could be recommended prior to invasion sport to help sustain sprint performance which is a critical component of match success. Although any benefit seen would be small, at an elite level these small changes may enhance overall team performance giving an advantage over oppositions.
|Date of Award||24 Feb 2022|
|Supervisor||John Babraj (Supervisor)|
- Invasion/team sports
- Interval training
- Lactate kinetics