Changes in submaximal and maximal measures of cardio-respiratory fitness resulting from 6-days of mountain walking.

Trekking is a popular activity associated with cardiovascular benefits. The aim of the present study was to investigate changes in the submaximal heart rate, oxygen uptake, oxygen pulse, and blood lactate concentration associated with a 6-day mountain walk. Over a 12-year period, 134 male (age 21.0 ± 1.4 years) and 124 female undergraduates (age 20.8 ± 1.6 years) participated. Three days before the trek submaximal and maximal laboratory measures were made on participants walking on a motorized treadmill using a breath-by-breath system to measure oxygen uptake (VO2) during exercise. Oxygen uptake and heart rate were recorded during steady-state exercise at treadmill gradients 0, 4, 8, 12, and 16%. Measurements were made, at the same time of day, two days after the trek. There were significant improvements in both the walking economy and the relative exercise intensity (%VO2max) at submaximal treadmill gradients 0-16%. Post-trek, heart rate was lower while oxygen pulse was higher, at each treadmill gradient. There was a significant increase in the maximal oxygen uptake for men (+2.7%) and women (+2.9%). The results of the present study suggest that improvements in cardiorespiratory fitness are associated with a 6-day mountain walk with no sex difference in the exercise response.      .

Effects of exercise intensity on anticipation timing performance during a cycling task at moderate and vigorous intensities in children aged 7-11 years.

This study examined coincidence anticipation timing performance at moderate and fast stimulus speeds before, during, and after a 15 minute cycling task. In a within-subject design, 24 children (18 males and 6 females) exercised on a cycle ergometer under two experimental conditions: exercise intensities of 50% (moderate) and 75% (vigorous) heart rate reserve. Coincidence anticipation timing was measured using the Bassin Anticipation Timer at stimulus speeds of 5 and 8 mph. A 2 (intensity) × 3 (time) repeated measures ANOVA was conducted to evaluate the effect of exercise intensity on coincidence anticipation performance before, during, and immediately after the cycling task. Results indicated that for absolute error there was no significant main effect for time (p = .633) or experimental condition (p = .782) at the 5 mph stimulus speed. However, there was a significant interaction effect between experimental condition and time (p = 0.026) at the 5 mph stimulus speed. At the 8 mph stimulus speed, there was no significant main effect for time (p = .910) or condition (p = .938), or interaction effect between experimental condition and time (p = .591). Cycling exercise at moderate intensity appears to influence anticipation timing performance during and immediately after exercise in children, but only when stimulus speeds are moderate in nature.

Using accelerometry to classify physical activity intensity in older adults: What is the optimal wear-site?

Abstract This study aimed to determine the optimal accelerometer wear-site specific cut-points for discrimination of the sedentary time, light physical activity and moderate-to-vigorous physical activity (MVPA) in older adults. Twenty-three adults (14 females) aged 55-77 years wore a GENEActiv accelerometer on their non-dominant wrist, dominant wrist, waist and dominant ankle whilst undertaking eight, five-minute bouts of activity: lay supine, seated reading, slow walking, medium walking, fast walking, folding laundry, sweeping and stationary cycling. VO2 was assessed concurrently using indirect calorimetry. Receiver-operating-characteristic (ROC) analyses were used to derive wear-site specific cut-points for classifying intensity. Indirect calorimetry indicated that being lay supine and seated reading were classified as sedentary (<1.5 METs), laundry as light (1.51-2.99 METs) and sweeping, slow, medium and fast walking and cycling all classified as moderate intensity (>3 METs). Areas under ROC curves indicated that the classification of sedentary activity was good for the non-dominant wrist and excellent for all other wear sites. Classification of MVPA was excellent for the waist and ankle, good for the waist and poor for the dominant and non-dominant wrists. Overall, the ankle location performed better than in other locations. Ankle-worn accelerometry appears to provide the most suitable wear-site to discriminate between sedentary time and MVPA in older adults.

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.

The impact of high and low-intensity exercise in adolescents with movement impairment.

Five to six percent of young people have movement impairment (MI) associated with reduced exercise tolerance and physical activity levels which persist into adulthood. To better understand the exercise experience in MI, we determined the physiological and perceptual responses during and following a bout of exercise performed at different intensities typically experienced during sport in youth with MI. Thirty-eight adolescents (11-18 years) categorised on the Bruininks-Oseretsky Test of Motor Proficiency-2 Short-Form performed a peak oxygen uptake bike test ([Formula: see text]) test at visit 1 (V1). At visits 2 (V2) and 3 (V3), participants were randomly assigned to both low-intensity (LI) 30min exercise at 50% peak power output (PPO50%) and high-intensity (HI) 30s cycling at PPO100%, interspersed with 30s rest, for 30min protocol (matched for total work). Heart rate (HR) and rating of perceived exertion (RPE) for legs, breathing and overall was measured before, during and at 1, 3 and 7-min post-exercise (P1, P3, P7). There was a significant difference in [Formula: see text] between groups (MI:31.5±9.2 vs. NMI:40.0±9.5ml⋅kg-1⋅min-1, p<0.05). PPO was significantly lower in MI group (MI:157±61 vs. NMI:216±57 W)(p<0.05). HRavg during HI-cycling was reduced in MI (140±18 vs. 157±14bpm, p<0.05), but not LI (133±18 vs. 143±17bpm, p>0.05). Both groups experienced similar RPE for breathing and overall (MI:7.0±3.0 vs. NMI:6.0±2.0, p>0.05) at both intensities, but reported higher legs RPE towards the end (p<0.01). Significant differences were found in HRrecovery at P1 post-HI (MI:128±25.9 vs. NMI:154±20.2, p<0.05) but not for legs RPE. Perceived fatigue appears to limit exercise in youth with MI in both high and low-intensity exercise types. Our findings suggest interventions reducing perceived fatigue during exercise may improve exercise tolerance and positively impact on engagement in physical activities.

Exploring the Metabolic and Perceptual Correlates of Self-Selected Walking Speed under Constrained and Un-Constrained Conditions.

Mechanisms underpinning self-selected walking speed (SSWS) are poorly understood. The present study investigated the extent to which SSWS is related to metabolism, energy cost, and/or perceptual parameters during both normal and artificially constrained walking. Fourteen participants with no pathology affecting gait were tested under standard conditions. Subjects walked on a motorized treadmill at speeds derived from their SSWS as a continuous protocol. RPE scores (CR10) and expired air to calculate energy cost (J.kg-1.m-1) and carbohydrate (CHO) oxidation rate (J.kg-1.min-1) were collected during minutes 3-4 at each speed. Eight individuals were re-tested under the same conditions within one week with a hip and knee-brace to immobilize their right leg. Deflection in RPE scores (CR10) and CHO oxidation rate (J.kg-1.min-1) were not related to SSWS (five and three people had deflections in the defined range of SSWS in constrained and unconstrained conditions, respectively) (p > 0.05). Constrained walking elicited a higher energy cost (J.kg-1.m-1) and slower SSWS (p < 0.05) versus normal walking. RPE (CR10) was not significantly different between walking conditions or at SSWS (p > 0.05). SSWS did not occur at a minimum energy cost (J.kg-1.m-1) in either condition, however, the size of the minimum energy cost to SSWS disparity was the same (Froude {Fr} = 0.09) in both conditions (p = 0.36). Perceptions of exertion can modify walking patterns and therefore SSWS and metabolism/ energy cost are not directly related. Strategies which minimize perceived exertion may enable faster walking in people with altered gait as our findings indicate they should self-optimize to the same extent under different conditions.

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.

Multi-modal characterization of rapid anterior hippocampal volume increase associated with aerobic exercise.

The hippocampus has been shown to demonstrate a remarkable degree of plasticity in response to a variety of tasks and experiences. For example, the size of the human hippocampus has been shown to increase in response to aerobic exercise. However, it is currently unknown what underlies these changes. Here we scanned sedentary, young to middle-aged human adults before and after a six-week exercise intervention using nine different neuroimaging measures of brain structure, vasculature, and diffusion. We then tested two different hypotheses regarding the nature of the underlying changes in the tissue. Surprisingly, we found no evidence of a vascular change as has been previously reported. Rather, the pattern of changes is better explained by an increase in myelination. Finally, we show that hippocampal volume increase is temporary, returning to baseline after an additional six weeks without aerobic exercise. This is the first demonstration of a change in hippocampal volume in early to middle adulthood suggesting that hippocampal volume is modulated by aerobic exercise throughout the lifespan rather than only in the presence of age related atrophy. It is also the first demonstration of hippocampal volume change over a period of only six weeks, suggesting that gross morphometric hippocampal plasticity occurs faster than previously thought.

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.

Motor impairment and its relationship to fitness in children.

OBJECTIVES: The aim of this work was to explore the physiological and perceptual limits to exercise in children with varying degrees of motor impairment, and the relationships to measures of health. DESIGN AND METHODS: In a group comparison design, 35 boys aged 12-15 years completed the Movement ABC test for the assessment of motor impairment, followed by an incremental cycle ergometer test to exhaustion for the assessment of maximal oxygen uptake (VO2peak), respiratory exchange ratio (RER), heart rate (HR) and rating of perceived exertion (RPE). Ten participants classified as having either high or no motor impairment also performed a maximal voluntary isometric contraction (MVIC) for the assessment of lower limb extensor strength. RESULTS: 18 boys were classified as having high motor impairment. There was a significant difference in peak (34.9 vs 48.5 mL kg/min), workload (12.5 vs 10.0 mL W), maximal HR (176 vs 188 bpm), maximal oxygen pulse (12.1 vs 15.9 mL beat) and MVIC (5.7 vs 9.1 Nm kg) between the high and non-motor impaired participants, respectively, (p<0.05). There was no significant difference in the RER or RPE between groups. CONCLUSIONS: When performing cycling ergometry, perceived exertion was not a limiting factor in children with high motor impairment. The lower maximal HR, coupled with reduced movement efficiency and muscle strength reported in this group, suggests that exercise is limited by impairment at the muscular level. This finding was supported by high RER values despite low maximal HR values attained at exercise cessation and reduced maximal strength. Perception of effort is not heightened in children with high motor impairment and future-exercise interventions should be focused on improving muscular condition in these participants to enable them to be better prepared to engage in physical activity for health.

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.