'Priming' exercise and O2 uptake kinetics during treadmill running.

We tested the hypothesis that priming exercise would speed V(O2) kinetics during treadmill running. Eight subjects completed a square-wave protocol, involving two bouts of treadmill running at 70% of the difference between the running speeds at lactate threshold (LT) and V(O2) max, separated by 6-min of walking at 4 km h(-1), on two occasions. Oxygen uptake was measured breath-by-breath and subsequently modelled using non-linear regression techniques. Heart rate and blood lactate concentration were significantly elevated prior to the second exercise bout compared to the first. However, V(O2) kinetics was not significantly different between the first and second exercise bouts (mean+/-S.D., phase II time constant, Bout 1: 16+/-3s vs. Bout 2: 16+/-4s; V(O2) slow component amplitude, Bout 1: 0.24+/-0.10 L min(-1)vs. Bout 2: 0.20+/-0.12 L min(-1); mean response time, Bout 1: 34+/-4s vs. Bout 2: 34+/-6s; P>0.05 for all comparisons). These results indicate that, contrary to previous findings with other exercise modalities, priming exercise does not alter V(O2) kinetics during high-intensity treadmill running, at least in physically active young subjects. We speculate that the relatively fast V(O2) kinetics and the relatively small V(O2) slow component in the control ('un-primed') condition negated any enhancement of V(O2) kinetics by priming exercise in this exercise modality.

The effects of contrast bathing and compression therapy on muscular performance.

UNLABELLED: Contrast bathing (CB) and compression garments (CG) are widely used to promote recovery. PURPOSE: To evaluate CB and CG as regeneration strategies after exercise-induced muscle damage (EIMD). METHODS: Baseline values of muscle soreness, serum creatine kinase (CK) and myoglobin (Mb), joint range of motion, limb girth, 10- or 30-m sprint, countermovement jump (CMJ), and five repetition maximum squat were completed by 26 young men who then undertook a resistance exercise challenge (REC) to induce EIMD: 6 x 10 parallel squats at 100% body weight with 5-s one repetition maximum eccentric squat superimposed onto each set. After the REC, subjects were separated into three intervention groups: CB, CG, and control (CONT). Forty-eight hours after REC, the subjects exercise performance was reassessed. CK and Mb were also measured +1, +24, and +48 h post-REC. RESULTS: CK was elevated at +24 h ( upward arrow140%; upward arrow161%; upward arrow270%), and Mb was elevated at +1 h ( upward arrow523%; upward arrow458%; upward arrow682%) in CB, CG, and CONT. Within-group large effect sizes for loge[CK] were found for CB at +24 h (0.80) and +48 h (0.84). Area under the [Mb] curve was lower in CB compared with CG and CONT (P < or = 0.05). At +48 h, significant differences from baseline were found in all groups for CMJ (CG, downward arrow5.1%; CB, downward arrow4.4%; CONT, downward arrow8.5%) and soreness ( upward arrow213%; upward arrow284%; upward arrow284%). Soreness transiently fell at +1 h compared with post-REC in the CB group. At +48 h, midthigh girth increased in CB ( upward arrow1.4%) and CONT ( upward arrow1.6%), whereas 30-m sprint time increased in CG ( upward arrow2%). CONCLUSION: No hierarchy of recovery effects was found. Neither contrast bathing nor compression acted to promote acute recovery from EIMD any more effectively than passive conditions, although contrast bathing may transiently attenuate postexercise soreness.

Assessment of an international breaststroke swimmer using a race readiness test.

Competitive swimmers routinely undertake a 7 x 200-m incremental step test to evaluate their fitness and readiness to compete.An exercise protocol more closely replicating competition swimming speeds may provide further insight into the swimmer's physiological and technical readiness for competition. This case study reports data over a 3-year period from 11 Race Readiness Tests, which were completed, in addition to the 7 x 200-m test, as an attempt to provide the swimmer and coach with a fuller assessment. For this individual, data provided objective information from which to assess training status and race readiness following a transition from 200-m to 100-m race training. Data also raised a question as to whether a 100-m maximal effort 10 minutes before another one actually enhances performance owing to a priming effect.

Effect of blood lactate sample site and test protocol on training zone prescription in rowing.

PURPOSE: To assess the effect of sample site (earlobe vs toe) and incremental exercise protocol (continuous vs discontinuous) on training zone prescription in rowing. METHODS: Twenty-six rowers performed two incremental exercise tests on an ergometer: (1) a five-step discontinuous test with 4-min stages and 30-W increment, with blood samples taken from the earlobe and toe at the start of the 1-min break between steps; (2) a continuous test, with 2-min stages and 30-W increment, with blood samples taken from the right first toe at the end of each stage. Blood was analyzed for lactate concentration. RESULTS: At a lactate concentration of 2 mmol x L(-1), the mean (95% CI) power output was 8.1 (+/- 15.4) W greater for the continuous protocol, the random error between the methods (1.96 x SD of differences) was +/- 58.8 W, and there was no evidence of any relationship between power output and error between methods. At a lactate concentration of 4 mmol x L(-1), the mean (95% CI) power output was 24.2 (+/- 17.0) W greater for the continuous protocol, and the random error was +/- 64.8 W. At 4 mmol x L(-1), systematic bias between methods increased with high power outputs. CONCLUSIONS: The continuous protocol with toe sampling led to higher power outputs for a given lactate concentration compared with the discontinuous protocol with earlobe sampling. This was partly due to the choice of sample site and largely due to the choice of protocol. This bias, and also random variability, makes direct comparison of these tests inappropriate.

Indices of electromyographic activity and the "slow" component of oxygen uptake kinetics during high-intensity knee-extension exercise in humans.

The control of pulmonary oxygen uptake (VO2) kinetics above the lactate threshold (LT) is complex and controversial. Above LT, VO2 for square-wave exercise is greater than predicted from the sub-LT VO2-WR relationship, reflecting the contribution of an additional "slow" component (VO2(sc)). Investigators have argued for a contribution to this slow component from the recruitment of fast-twitch muscle fibres, which are less aerobically efficient than slow-twitch fibres. Six healthy subjects performed a rapid-incremental bilateral knee-extension exercise test to the limit of tolerance for the estimation of VO2(peak), ventilatory threshold (VT), and the difference between VO2(peak) and VO2 at VT (Delta). Subjects then completed three repetitions of square-wave exercise at 30% of VT for 10 min (moderate intensity), and at VT + 25%Delta (heavy intensity) for 20 min. Pulmonary gas exchange was measured breath-by-breath. Surface EMG was recorded from m. rectus femoris; integrated EMG (IEMG) and mean power frequency (MPF) were derived for successive contractions. In comparison to moderate-intensity exercise, the phase 2 VO2 kinetics in heavy exercise were marginally slower than for moderate-intensity exercise (time constant (+/- SD) 25 +/- 9 and 22 +/- 10 s, respectively; NS), with a discernible VO2(sc) (VO2 difference between minutes 6 and 3 of exercise: 74 +/- 21 and 0 +/- 20 ml min(-1), respectively). However, there was no significant change in IEMG or MPF, either in the moderate domain or in the heavy domain over the period when the slow component was manifest. These observations argue against an appreciable preferential recruitment of fast-twitch units with high force-generating characteristics and fast sarcolemmal conduction velocities in concert with the development of the VO2 slow component during heavy-intensity knee-extensor exercise. The underlying mechanism(s) remains to be resolved.