James P. Gavin

Reproducibility of lactate markers during 4 and 8 min stage incremental running: A pilot study

OBJECTIVES This study examined the reproducibility of speed corresponding to specific lactate markers during incremental treadmill running of normal and prolonged stage durations. DESIGN Nineteen healthy participants (14 male, 5 female) performed repeated, incremental treadmill running trials of 4 and 8 min stages on separate days to examine the test-retest reproducibility of speed at lactate markers. Two trials were completed for each duration in a randomised order. METHODS Fingertip blood samples drawn upon stage completion were analysed for plasma lactate, then used to determine running speed at: 2.0, 3.5, and 4.0 mmol l(-1) fixed blood lactate accumulations (FBLA), a 1 mmol l(-1) rise from baseline, and the markers: the deviation maximum (Dmax), the Dmax of the second curve derivative (D2L(max)), the lactate threshold (LT) and log-log LT. RESULTS The 2.0 mmol l(-1) FBLA reported the lowest mean bias between 4 min trials (-0.06 km h(-1)), with the narrowest limits of agreement (LoA) (-1.78 to 1.66 km h(-1)). The Dmax had the second lowest bias (0.14 km h(-1)), D2L(max) the second narrowest LoA (-1.93 to 2.90 km h(-1)). For 8 min stages, the 1 mmol l(-1) rise demonstrated, low mean bias (-0.13 km h(-1)) and narrowest LoA (-1.22 to 0.97 km h(-1)) between trials. CONCLUSIONS This preliminary report suggests the reproducibility of running speed at lactate summary markers is influenced by stage duration for incremental treadmill running. Varied marker reproducibility between 4 and 8 min stages indicates different blood lactate response, and therefore workload calculation, according to stage length. Consideration of marker construct is recommended.

Neuromuscular responses to mild-muscle damaging eccentric exercise in a low glycogen state.

The aim of this study was to examine the effect of low muscle glycogen on the neuromuscular responses to maximal eccentric contractions. Fourteen healthy men (22 ± 3 years) performed single-leg cycling (20 min at ~75% maximal oxygen uptake (V̇O2 max); eight 90 s sprints at a 1:1 work-to-rest ratio (5% decrements from 90% to 55% V̇O2 max until exhaustion) the evening before 100 eccentric (1.57 rads(-1)) with reduced (RED) and normal glycogen (NORM). Neuromuscular responses were measured during and up to 48 h after with maximal voluntary and involuntary (twitch, 20 Hz and 50 Hz) isometric contractions. During eccentric contractions, peak torque decreased (RED: -16.1 ± 2.5%; NORM: -6.2 ± 5.1%) and EMG frequency increased according to muscle length. EMG activity decreased for RED only. After eccentric contractions, maximal isometric force was reduced up to 24h for NORM (-13.5 ± 5.8%) and 48 h for RED (-7.4 ± 10.9%). Twelve hours after eccentric contractions, twitch force and the 20:50 Hz ratio were decreased for RED but not for NORM. Immediate involuntary with prolonged voluntary force loss suggests that reduced glycogen is associated with increased susceptibility to mild muscle-damaging eccentric exercise with contributions of peripheral and central mechanisms to be different during recovery.

The Accumulative Effect of Concentric-Biased and Eccentric-Biased Exercise on Cardiorespiratory and Metabolic Responses to Subsequent Low-Intensity Exercise: A Preliminary Study

Abstract The study investigated the accumulative effect of concentric-biased and eccentric-biased exercise on cardiorespiratory, metabolic and neuromuscular responses to low-intensity exercise performed hours later. Fourteen young men cycled at low-intensity (~60 rpm at 50% maximal oxygen uptake) for 10 min before, and 12 h after: concentric-biased, single-leg cycling exercise (CON) (performed ~19:30 h) and eccentric-biased, double-leg knee extension exercise (ECC) (~06:30 h the following morning). Respiratory measures were sampled breath-by-breath, with oxidation values derived from stoichiometry equations. Knee extensor neuromuscular function was assessed before and after CON and ECC. Cardiorespiratory responses during low-intensity cycling were unchanged by accumulative CON and ECC. The RER was lower during low-intensity exercise 12 h after CON and ECC (0.88 ± 0.08), when compared to baseline (0.92 ± 0.09; p = 0.02). Fat oxidation increased from baseline (0.24 ± 0.2 g·min1) to 12 h after CON and ECC (0.39 ± 0.2 g·min1; p = 0.01). Carbohydrate oxidation decreased from baseline (1.59 ± 0.4 g·min-1) to 12 h after CON and ECC (1.36 ± 0.4 g·min1; p = 0.03). These were accompanied by knee extensor force loss (right leg: -11.6%, p < 0.001; left leg: -10.6%, p = 0.02) and muscle soreness (right leg: 2.5 ± 0.9, p < 0.0001; left leg: 2.3 ± 1.2, p < 0.01). Subsequent concentric-biased and eccentric-biased exercise led to increased fat oxidation and decreased carbohydrate oxidation, without impairing cardiorespiration, during low-intensity cycling. An accumulation of fatiguing and damaging exercise increases fat utilisation during low intensity exercise performed as little as 12 h later.

The effects of knee joint angle on neuromuscular activity during electrostimulation in healthy older adults

Introduction Electrostimulation devices stimulate the common peroneal nerve, producing a calf muscle-pump action to promote venous circulation. Whether knee joint angle influences calf neuromuscular activity remains unclear. Our aim was to determine the effects of knee joint angle on lower limb neuromuscular activity during electrostimulation. Methods Fifteen healthy, older adults underwent 60 min of electrostimulation, with the knee joint at three different angles (0°, 45° or 90° flexion; random order; 20 min each). Outcome variables included electromyography of the peroneus longus, tibialis anterior and gastrocnemius medialis and lateralis and discomfort. Results Knee angle did not influence tibialis anterior and peroneus longus neuromuscular activity during electrostimulation. Neuromuscular activity was greater in the gastrocnemius medialis (p = 0.002) and lateralis (p = 0.002) at 90°, than 0° knee angle. Electrostimulation intensity was positively related to neuromuscular activity for each muscle, with a knee angle effect for the gastrocnemius medialis (p = 0.05). Conclusion Results suggest that during electrostimulation, knee joint angle influenced gastrocnemii neuromuscular activity; increased gastrocnemius medialis activity across all intensities (at 90°), when compared to 0° and 45° flexion; and did not influence peroneus longus and tibialis anterior activity. Greater electrostimulation-evoked gastrocnemii activity has implications for producing a more forceful calf muscle-pump action, potentially further improving venous flow.

Stair negotiation as a rehabilitation intervention for enhancing recovery following total hip and knee replacement surgery

BACKGROUND Total hip replacement (THR) and total knee replacement (TKR) are common orthopaedic procedures. However, an optimal programme for post-operative rehabilitation has yet to be established. Stair negotiation is a challenging, habitual task, regularly used as a post-operative functional outcome measure; yet as a physical rehabilitation intervention it appears to be rarely used. AIM The review purpose was to investigate the effectiveness of stair climbing as a rehabilitation intervention for THR and TKR patients. METHODS MEDLINE, PsycINFO, Science Citation Index, CINAHL, SPORTDiscus and the Cochrane Database of Systematic Reviews were searched. The systematic review targeted studies using stair negotiation as a rehabilitation intervention. Randomised and non-randomised controlled trials, pilot studies, and case studies were included; systematic reviews and meta-analyses were excluded. RESULTS Of 650 articles identified, ten studies were eligible for review. A predefined data table to extract information from selected studies was used. Of the ten identified reports, two prehabilitation and eight rehabilitation studies included stair negotiation exercises as part of multi-modal physical interventions. Outcome measures were classified as: functional self-reported, perceptual, psychological and those relating to quality of life. CONCLUSION Studies were methodologically heterogeneous and typically lacked adequate control groups. It was not possible to determine the impact of stair negotiation exercise on the positive outcomes of interventions. Stair negotiation warrants further investigation as a rehabilitation activity.

Placement experience and learning motivations in higher education

Purpose – Placement-based learning is claimed to benefit educational outcomes in undergraduate programmes, with students gaining employability skills and the application of skill-sets in “real world” situations. Most courses incorporate experiential learning; however, work placements remain exclusive to the aims of the academic programme. The purpose of this paper is to explore the changing learning motivations between students enroled on: a practical-based programme, involving work placement (BA adventure education (Ad Ed)); and a study-based programme (BSc sport and exercise science (SES)). In addition, motivation was examined between courses at each year. Design/methodology/approach – A 44 item Motivated Strategies for Learning Questionnaire was completed by first and final year undergraduates studying BA Ad Ed and BSc SES courses in the academic year 2011/2012. Questionnaires were triangulated with focus groups, lecturer observations and statistical analyses. Findings – Learning motivation was influenced by: knowledge of academic grades; link between theoretical content and work experience; opportunity for reflection; and multidisciplinary nature of degree programmes. Furthermore, the majority of final year Ad Ed students showed understanding of the job market, degree transferability and career availability upon graduation. Originality/value – Where placement experience prepares British undergraduate learners for employment and provides insight into career demand, placements may also demotivate, particularly where careers do not necessitate degree qualification.

Effect of eccentric exercise with reduced muscle glycogen on plasma interleukin-6 and neuromuscular responses of musculus quadriceps femoris

Eccentric exercise can result in muscle damage and interleukin-6 (IL-6) secretion. Glycogen availability is a potent stimulator of IL-6 secretion. We examined effects of eccentric exercise in a low-glycogen state on neuromuscular function and plasma IL-6 secretion. Twelve active men (23 ± 4 yr, 179 ± 5 cm, 77 ± 10 kg, means ± SD) completed two downhill treadmill runs (gradient, -12%, 5 × 8 min; speed, 12.1 ± 1.1 km/h) with normal (NG) and reduced muscle glycogen (RG) in randomized order and at least 6 wk apart. Muscle glycogen was reduced using an established cycling protocol until exhaustion and dietary manipulation the evening before the morning run. Physiological responses were measured up to 48 h after the downhill runs. During recovery, force deficits of musculus quadriceps femoris by maximal isometric contractions were similar. Changes in low-frequency fatigue were larger with RG. Voluntary activation and plasma IL-6 levels were similar in recovery between conditions. It is concluded that unaccustomed, damaging eccentric exercise with low muscle glycogen of the m. quadriceps femoris 1) exacerbated low-frequency fatigue but 2) had no additional effect on IL-6 secretion. Neuromuscular impairment after eccentric exercise with low muscle glycogen appears to have a greater peripheral component in early recovery.