Effect of Work: Rest Ratio on Cycling Performance Following Sprint Interval Training: A Randomized Control Trial.

Lloyd Jones, MC, Morris, MG, and Jakeman, JR. Effect of work: Rest ratio on cycling performance following sprint interval training: A randomized control trial. J Strength Cond Res 33(12): 3263-3268, 2019-Sprint interval training (SIT) has been shown to improve performance measures in a range of individuals, and it is understood that different responses can be elicited from different training protocols. However, consideration of changes in work to rest ratios could offer important insight into optimizing training programs. The purpose of this study was to investigate the effect of 3 different work to rest ratios on exercise performance. Thirty-six male and female subjects were randomly allocated to 1 of 3 training groups or a nontraining control group. Training consisted of 10 × 6 second "all-out" sprints on a cycle ergometer, with a 1:8, 1:10, or 1:12 work-to-rest ratio. Performance data, including peak power output, performance decrement, and 10-km time trial performance data were collected before and after 2 weeks of SIT. There were significant (p ≤ 0.05) improvements in all parameters for the training groups, but no changes were observed in the control condition. Peak power increased by 57.2, 50.7, and 53.7 W in the 1:8, 1:10 and 1:12 groups, respectively, with no significant differences in response between conditions. Time trial performance improved significantly in all 3 training conditions (29.4, 8.7, and 25.1 seconds in the 1:8, 1:10, and 1:12 groups), while worsening in the control group. All training conditions resulted in significant improvements in performance, but there were no significant differences in improvement for any of the groups. Any of the 3 stated that work to rest ratios would be appropriate for use with athletes and allow some level of personal preference for those interested in using the protocol.

High-intensity exhaustive exercise reduces long-interval intracortical inhibition.

The development of fatigue during single-joint isolated muscle contractions is accompanied by an increase in long-interval intracortical inhibition (LICI). However, the effect of whole-body locomotor endurance exercise on LICI is unknown. Eighteen healthy men completed three exercise trials on a cycle ergometer. The first trial was completed to determine the lactate threshold (LT) and maximal oxygen uptake ([Formula: see text]). The remaining two trials (familiarisation and experimental) involved cycling to volitional exhaustion at an intensity equivalent to halfway between the LT and [Formula: see text] (50%Δ). Responses to stimulation of the femoral nerve [motor nerve stimulation (MNS)] and motor cortex [transcranial magnetic stimulation (TMS)] were determined pre- and post-exercise to determine the level of peripheral fatigue [potentiated quadriceps twitch (Qtw,pot)] and central fatigue [voluntary activation measured by MNS and TMS (VAMNS and VATMS, respectively)]. Corticospinal excitability (motor evoked potentials) and intracortical inhibition [LICI and corticospinal silent period (SP)] were also measured from electromyography recordings on the vastus lateralis. There were exercise-induced reductions in maximal voluntary contraction torque (- 21 ± 10%), Qtw,pot (- 37 ± 18%), VAMNS (- 7 ± 7%) and VATMS (- 8 ± 10) (all P < 0.01). There were increases in the LICI ratio and reductions in SP duration from pre- to post-exercise (mean absolute change of 16 ± 14% and - 31 ± 28 s, respectively) (both P < 0.01). The pre- and post-exercise MEP amplitudes were not different (P = 0.86). The neural inhibitory circuits that mediate the LICI and SP became less excitable with fatigue following high-intensity exhaustive cycling, which could be important in the aetiology of central fatigue during whole-body locomotor endurance exercise.

The relationship of gross upper and lower limb motor competence to measures of health and fitness in adolescents aged 13-14 years.

INTRODUCTION: Motor competence (MC) is an important factor in the development of health and fitness in adolescence. AIMS: This cross-sectional study aims to explore the distribution of MC across school students aged 13-14 years old and the extent of the relationship of MC to measures of health and fitness across genders. METHODS: A total of 718 participants were tested from three different schools in the UK, 311 girls and 407 boys (aged 13-14 years), pairwise deletion for correlation variables reduced this to 555 (245 girls, 310 boys). Assessments consisted of body mass index, aerobic capacity, anaerobic power, and upper limb and lower limb MC. The distribution of MC and the strength of the relationships between MC and health/fitness measures were explored. RESULTS: Girls performed lower for MC and health/fitness measures compared with boys. Both measures of MC showed a normal distribution and a significant linear relationship of MC to all health and fitness measures for boys, girls and combined genders. A stronger relationship was reported for upper limb MC and aerobic capacity when compared with lower limb MC and aerobic capacity in boys (t=-2.21, degrees of freedom=307, P=0.03, 95% CI -0.253 to -0.011). CONCLUSION: Normally distributed measures of upper and lower limb MC are linearly related to health and fitness measures in adolescents in a UK sample. TRIAL REGISTRATION NUMBER: NCT02517333.

High but not moderate-intensity endurance training increases pain tolerance: a randomised trial.

PURPOSE: To examine the effect of high-intensity interval training (HIIT) compared to volume-matched moderate-intensity continuous training (CONT) on muscle pain tolerance and high-intensity exercise tolerance. METHODS: Twenty healthy adults were randomly assigned (1:1) to either 6 weeks of HIIT [6-8 × 5 min at halfway between lactate threshold and maximal oxygen uptake (50%Δ)] or volume-matched CONT (~60-80 min at 90% lactate threshold) on a cycle ergometer. A tourniquet test to examine muscle pain tolerance and two time to exhaustion (TTE) trials at 50%Δ to examine exercise tolerance were completed pre- and post-training; the post-training TTE trials were completed at the pre-training 50%Δ (same absolute-intensity) and the post-training 50%Δ (same relative-intensity). RESULTS: HIIT and CONT resulted in similar improvements in markers of aerobic fitness (all P ≥ 0.081). HIIT increased TTE at the same absolute- and relative-intensity as pre-training (148 and 43%, respectively) to a greater extent than CONT (38 and -4%, respectively) (both P ≤ 0.019). HIIT increased pain tolerance (41%, P < 0.001), whereas CONT had no effect (-3%, P = 0.720). Changes in pain tolerance demonstrated positive relationships with changes in TTE at the same absolute- (r = 0.44, P = 0.027) and relative-intensity (r = 0.51, P = 0.011) as pre-training. CONCLUSION: The repeated exposure to a high-intensity training stimulus increases muscle pain tolerance, which is independent of the improvements in aerobic fitness induced by endurance training, and may contribute to the increase in high-intensity exercise tolerance following HIIT.

Impact of time and work:rest ratio matched sprint interval training programmes on performance: A randomised controlled trial.

OBJECTIVES: The aim of this study was to examine the effects of a short training intervention using two repeated sprint protocols matched for total sprint duration and work:rest ratio. DESIGN: Randomised-controlled trial. METHODS: Thirty physically active males were randomly allocated to one of two sprint training groups: a 6s group, a 30s group or a non-exercising control. The training groups were matched for work:rest ratio and total sprint time per session, and completed 6 training sessions over a 2-week period. Before and after the 2 week training period, participants completed a VO2max test and a 10km time trial on a cycle ergometer. RESULTS: Time trial performance increased significantly by 5.1% in 6s (630±115s to 598±92s; p<0.05) and 6.2% in 30s (579±68s to 543±85s; p<0.05) from baseline testing, but there was no significant change in the control group (p>0.05), and no significant difference between exercise groups (p>0.05). The 6s group increased peak power output by 9.0% (from 1092±263W to 1181±248W; p<0.05) from sprint session 1 to 6, and the 30s group by 20.0% (1041±161W to 1237±159W; p<0.05). CONCLUSIONS: This study indicates that both 6 and 30s bouts of repeated sprint exercise, matched for total sprint duration and W:R can improve athletic performance.

Reliability of single and paired-pulse transcranial magnetic stimulation in the vastus lateralis muscle.

INTRODUCTION: Transcranial magnetic stimulation (TMS) is an important tool to examine neurological pathologies, movement disorders, and central nervous system responses to exercise, fatigue, and training. The reliability has not been examined in a functional locomotor knee extensor muscle. METHODS: Within- (n = 10) and between-day (n = 16) reliability of single and paired-paired pulse TMS was examined from the active vastus lateralis. RESULTS: Motor evoked potential amplitude and cortical silent period duration showed good within- and between-day reliability (intraclass correlation coefficient [ICC] ≥ 0.82). Short- and long-interval intracortical inhibition (SICI and LICI, respectively) demonstrated good within-day reliability (ICC ≥ 0.84). SICI had moderate to good between-day reliability (ICC ≥ 0.67), but LICI was not repeatable (ICC = 0.47). Intracortical facilitation showed moderate to good within-day reliability (ICC ≥ 0.73) but poor to moderate reliability between days (ICC ≥ 0.51). CONCLUSIONS: TMS can reliably assess cortical function in a knee extensor muscle. This may be useful to examine neurological disorders that affect locomotion.

Alterations in peripheral muscle contractile characteristics following high and low intensity bouts of exercise.

The aim of this study was to monitor muscle contractile performance in vivo, using an electrical stimulation protocol, immediately following an acute high and low intensity exercise session conducted at the same average intensity performed on a cycle ergometer. Eighteen healthy males (25.1 ± 4.5 years, 81.6 ± 9.8 kg, 1.83 ± 0.06 m; mean ± SD) participated in the study. On two occasions, separated by 1 week, subjects completed a high and low intensity exercise session in a random order on a cycle ergometer, performing equal total work in each. At the end of each test, a muscle performance test using electrical stimulation was performed within 120 s. Post-exercise muscle data were compared to the subjects' rested muscle. We found a reduction in muscle contractile performance following both high and low intensity exercise protocols but a greater reduction in maximal voluntary contraction (MVC) (P < 0.01), rate of torque development (RTD) (P < 0.001), rate of relaxation (RR(½)), (P < 0.001) the 60 s slope of the fatigue protocol (P < 0.01) and torque frequency response (P < 0.05) following the high intensity bout. Importantly muscle performance remained reduced 1 h following high intensity exercise but was recovered following low intensity exercise. Muscle function was significantly reduced following higher intensity intermittent exercise in comparison to lower intensity exercise even when the average overall intensity was the same. This study is the first to demonstrate the sensitivity of muscle contractile characteristics to different exercise intensities and the impact of higher intensity bursts on muscle performance.

Muscle contractile characteristics: relationship to high-intensity exercise.

We investigated the relationship between muscle contractile characteristics, collected using percutaneous electrical stimulation, and high-intensity exercise performance. Seventeen participants performed a muscle performance test for the calculation of rate of torque development (RTD), rate of relaxation (RR(1/2)), rate of fatigue and fatigue resistance. On a second visit the participants completed a Wingate cycle ergometer test with peak power, mean power, fatigue index and fatigue rate calculated. The muscle fatigue index related significantly to the WAnT fatigue index and fatigue rate (p < 0.01). The change in rate of torque development (%DeltaRTD) was also related significantly to the fatigue rate (W/s) during the WAnT. Subjects displaying the greatest reduction in RTD had the greatest fatigue rate during the WAnT and greater fatigue during the electrical stimulation protocol. There were no significant relationships between peak (r 0.36; p > 0.01) or mean power (r -0.11, p > 0.01) with any of the muscle performance measures. These findings demonstrate that muscle contractile characteristics, elicited during standardised in vivo electrical stimulation, relate to performance during a Wingate anaerobic test. They suggest that muscle contraction characteristics play an important role in high-intensity exercise performance and indicate that electrical stimulation protocols can be a useful additional tool to explore muscle contraction characteristics in relation to exercise performance and trainability.

Relationships between muscle fatigue characteristics and markers of endurance performance.

The aim of this study was to examine the relationship of a range of in-vivo whole muscle characteristics to determinants of endurance performance. Eleven healthy males completed a cycle ergometer step test to exhaustion for the determination of the lactate threshold, gross mechanical efficiency, peak power and VO2max. On two separate occasions, contractile and fatigue characteristics of the quadriceps femoris were collected using a specially designed isometric strength-testing chair. Muscle fatigue was then assessed by stimulating the muscle for 3 minutes. Force, rate of force development and rates of relaxation were calculated at the beginning and end of the 3 minute protocol and examined for reliability and in relation to lactate threshold, VO2max, gross mechanical efficiency and peak power. Muscle characteristics, rate of force development and relaxation rate were demonstrated to be reliable measures. Force drop off over the 3 minutes (fatigue index) was related to lactate threshold (r = -0.72 p » 0.01) but not to VO2max. The rate of force development related to the peak power at the end of the cycle ergometer test (r = -0.75 p » 0.01). Rates of relaxation did not relate to any of the performance markers. We found in-vivo whole muscle characteristics, such as the fatigue index and rate of force development, relate to specific markers of peripheral, but not to central, fitness components. Our investigation suggests that muscle characteristics assessed in this way is reliable and could be feasibly utilised to further our understanding of the peripheral factors underpinning performance. Key pointsParticipants with a high lactate threshold displayed greater fatigue resistance in the electrical stimulation test.Muscle performance characteristics relate to specific components of endurance performance.The electrical stimulation protocol could be a useful technique, alongside other established measures, when constructing a physiological profile of a participant.