Alan Ruddock

Reproducibility of cutaneous thermal hyperaemia assessed by laser Doppler flowmetry in young and older adults

OBJECTIVES The primary objective of this study was to assess the inter-day reproducibility of cutaneous thermal hyperaemia, as assessed using integrating-probe laser Doppler flowmetry (LDF), in young and older men. A secondary objective was to identify the most reproducible form of data expression. METHODS Cutaneous thermal hyperaemia was assessed on the forearm in 14 young (25±1 year) and 14 older (65±1 year) men, using integrating-probe LDF. The test was repeated 7-14 days later. The baseline, initial peak, and plateau phases of the data traces were identified and expressed as raw cutaneous vascular conductance (CVC), CVC normalised to baseline (%CVC(BL)), and CVC normalised to 44°C vasodilatation (%CVC(MAX)). Reproducibility was assessed using the coefficient of variation (CV) and intraclass correlation coefficient (ICC) statistics. RESULTS The inter-day reproducibility was dependent on how the data were expressed. The reproducibility of the initial peak and plateau was equally acceptable in both young and older adults when data were expressed as %CVC(MAX) (e.g., CVs ranging from 4 to 11%). However, the baseline phase was poorly reproducible in both groups irrespective of the data presentation method used (e.g., CVs ranging from 25 to 35%). Furthermore, expressing data as raw CVC or as %CVC(BL) generally showed poor reproducibility for both groups and all phases of the test (e.g., CVs ranging from 15 to 39%). CONCLUSION Integrating-probe LDF is a reproducible technique to assess cutaneous thermal hyperaemia on the forearm when data are expressed as %CVC(MAX) in healthy young and older adults without history of hypertension or taking system drugs.

Role of sensory nerves in the rapid cutaneous vasodilator response to local heating in young and older endurance‐trained and untrained men

The ability to increase skin blood flow (SkBF) rapidly in response to local heating is diminished with advanced age; however, the mechanisms are unclear. The primary aim of this study was to investigate the role of sensory nerves in this age‐related change. A secondary aim was to investigate the effect of aerobic fitness on sensory nerve‐mediated vasodilatation in young and aged skin. We measured SkBF (using laser Doppler flowmetry) in young and older endurance‐trained and untrained men (n = 7 in each group) at baseline and during 35 min of local skin heating to 42°C at two sites on the ventral forearm. One site was pretreated with topical anaesthetic cream to block local sensory nerve function. Cutaneous vascular conductance (CVC) was calculated as SkBF divided by mean arterial pressure and normalized to maximal values (CVCmax) achieved during local heating to 44°C. At the untreated site, the rapid vasodilatation during the first ∼5 min of local heating (initial peak) was lower in the older untrained group (68 ± 3%CVCmax) compared with all other groups (young trained, 76 ± 4%CVCmax; young untrained, 75 ± 5%CVCmax; and older trained, 81 ± 3%CVCmax; P < 0.05). Sensory nerve blockade abolished these differences among the groups (P > 0.05). The contribution of sensory nerve‐mediated vasodilatation was lower in the older untrained group compared with all other groups (P< 0.05). Our results suggest that the age‐related decline in the rapid vasodilator response to local heating in human skin is explained by diminished sensory nerve‐mediated vasodilatation. These findings also indicate that this age‐related change can be prevented through participation in regular aerobic exercise.

Aging and aerobic fitness affect the contribution of noradrenergic sympathetic nerves to the rapid cutaneous vasodilator response to local heating

Sedentary aging results in a diminished rapid cutaneous vasodilator response to local heating. We investigated whether this diminished response was due to altered contributions of noradrenergic sympathetic nerves by assessing 1) the age-related decline and 2) the effect of aerobic fitness. Using laser-Doppler flowmetry, we measured skin blood flow (SkBF) in young (24 ± 1 yr) and older (64 ± 1 yr) endurance-trained and sedentary men (n = 7 per group) at baseline and during 35 min of local skin heating to 42°C at 1) untreated forearm sites, 2) forearm sites treated with bretylium tosylate (BT), which prevents neurotransmitter release from noradrenergic sympathetic nerves, and 3) forearm sites treated with yohimbine + propranolol (YP), which antagonizes α- and β-adrenergic receptors. SkBF was converted to cutaneous vascular conductance (CVC = SkBF/mean arterial pressure) and normalized to maximal CVC (%CVC(max)) achieved by skin heating to 44°C. Pharmacological agents were administered using microdialysis. In the young trained group, the rapid vasodilator response was reduced at BT and YP sites (P < 0.05); by contrast, in the young sedentary and older trained groups, YP had no effect (P > 0.05), but BT did (P > 0.05). Neither BT nor YP affected the rapid vasodilator response in the older sedentary group (P > 0.05). These data suggest that the age-related reduction in the rapid vasodilator response is due to an impairment of sympathetic-dependent mechanisms, which can be partly attenuated with habitual aerobic exercise. Rapid vasodilation involves noradrenergic neurotransmitters in young trained men and nonadrenergic sympathetic cotransmitters (e.g., neuropeptide Y) in young sedentary and older trained men, possibly as a compensatory mechanism. Finally, in older sedentary men, the rapid vasodilation appears not to involve the sympathetic system.

Reliability of Intestinal Temperature Using an Ingestible Telemetry Pill System During Exercise in a Hot Environment

Abstract Ruddock, AD, Tew, GA, and Purvis, AJ. Reliability of intestinal temperature using an ingestible telemetry pill system during exercise in a hot environment. J Strength Cond Res 28(3): 861–869, 2014—Ingestible telemetry pill systems are being increasingly used to assess the intestinal temperature during exercise in hot environments. The purpose of this investigation was to assess the interday reliability of intestinal temperature during an exercise-heat challenge. Intestinal temperature was recorded as 12 physically active men (25 ± 4 years, stature 181.7 ± 7.0 cm, body mass 81.1 ± 10.6 kg) performed two 60-minute bouts of recumbent cycling (50% of peak aerobic power [watts]) in an environmental chamber set at 35° C 50% relative humidity 3–10 days apart. A range of statistics were used to calculate the reliability, including a paired t-test, 95% limits of agreement (LOA), coefficient of variation (CV), standard error of measurement (SEM), Pearsons correlation coefficient (r), intraclass correlation coefficient (ICC), and Cohens d. Statistical significance was set at p ⩽ 0.05. The method indicated a good overall reliability (LOA = ±0.61° C, CV = 0.58%, SEM = 0.12° C, Cohens d = 0.12, r = 0.84, ICC = 0.84). Analysis revealed a statistically significant (p = 0.02) mean systematic bias of −0.07 ± 0.31° C, and the investigation of the Bland–Altman plot suggested the presence of heteroscedasticity. Further analysis revealed the minimum “likely” change in intestinal temperature to be 0.34° C. Although the method demonstrates a good reliability, researchers should be aware of heteroscedasticity. Changes in intestinal temperature >0.34° C as a result of exercise or an intervention in a hot environment are likely changes and less influenced by error associated with the method.

Effect of age on cutaneous vasomotor responses during local skin heating

This study examined the effect of ageing on the low-frequency oscillations (vasomotion) of skin blood flow in response to local heating (LH). Skin blood flow was assessed by laser-Doppler flowmetry on the forearm at rest (33°C) and in response to LH of the skin to both 42°C and 44°C in 14 young (24±1years) and 14 older (64±1years) participants. Vasomotion was analyzed using a wavelet transform to investigate power of the frequency intervals associated with endothelial, neural, myogenic, respiratory, and cardiac activities of the laser-Doppler signal. Laser-Doppler flux increased in both groups with LH (both d>1.8, p<0.001). Endothelial activity increased in both groups following LH to 42°C (young d=1.4, p<0.001; older d=1.2, p=0.005) and 44°C (young d=1.4, p=0.001; older d=1.5, p=0.005). Endothelial activity was higher in the young compared to older group during LH to 42°C (d=1.4, p=0.017) and 44°C (d=1.5, p=0.004). In response to LH to 42°C and 44°C, neural activity in both groups was decreased (both groups and conditions: d>1.2, p<0.001). Myogenic activity increased in the younger group following LH to 44°C (d=1, p=0.042), while in the older group, myogenic activity increased following LH to 42°C (d=1.2, p=0.041) and 44°C (d=1.1, p=0.041). Respiratory and cardiac activities increased in both groups during LH to 42°C and 44°C (All: d>0.9, p<0.017). There were no differences in wavelet amplitude between younger and older in the neural (d=0.1, p>0.7), myogenic (d=0.3, p>0.7), respiratory (d=0.4, p>0.6), and cardiac (d=0.1, p>0.7) frequency intervals. These data indicate that LH increases cutaneous endothelial and myogenic activity, while decreasing neural activity. Furthermore, ageing reduces the increase in cutaneous endothelial activity in response to LH.

Dietary nitrate does not affect physical activity or outcomes in healthy older adults in a randomized, cross-over trial

Although dietary nitrate (NO3-) ingestion appears to enhance exercise capacity and performance in young individuals, inconclusive findings have been reported in older people. Therefore, we conducted a double-blind, crossover randomized clinical trial using beetroot juice in older healthy participants, who were classified as normal weight and overweight. We tested whether consumption of beetroot juice (a rich source of NO3-) for 1 week would increase nitric oxide bioavailability via the nonenzymatic pathway and enhance (1) exercise capacity during an incremental exercise test, (2) physical capability, and (3) free-living physical activity. Twenty nonsmoking, healthy participants between 60 and 75 years of age and with a body mass index of 20.0 to 29.9 kg/m2 were included. Presupplementation and postsupplementation resting, submaximal, maximal, and recovery gas exchanges were measured. Physical capability was measured by hand-grip strength, time-up-and-go, repeated chair rising test, and 10-m walking speed. Free-living physical activity was assessed by triaxal accelerometry. Changes in urinary and plasmaNO3-concentrations were measured by gas chromatography-mass spectrometry. Nineteen participants (male-to-female ratio, 9:10) completed the study.Beetroot juice increased significantly both plasma and urinary NO3-concentrations (P<.001) when compared with placebo. Beetroot juice did not influence resting or submaximal and maximal oxygen consumption during the incremental exercise test. In addition, measures of physical capability and physical activity levels measured in free-living conditions were not modified by beetroot juice ingestion. The positive effects of beetroot juice ingestion on exercise performance seen in young individuals were not replicated in healthy, older adults. Whether aging represents a modifier of the effects of dietary NO3-on muscular performance is not known, and mechanistic studies and larger trials are needed to test this hypothesis.

Dietary nitrate does not modify blood pressure and cardiac output at rest and during exercise in older adults: a randomised cross-over study

Abstract Dietary nitrate (NO3-) supplementation has been associated with improved vascular and metabolic health. We conducted a double-blind, cross-over, placebo-controlled RCT to investigate the effects of 7-d consumption of beetroot juice compared with placebo on (1) blood pressure (BP) measured in resting conditions and during exercise, (2) cardiac and peripheral vascular function and (3) biomarkers of inflammation, oxidative stress and endothelial integrity. Twenty non-smoking healthy participants aged 60–75 years and BMI 20.0–29.9 kg/m2 were recruited. Measurement was conducted before and after each 7-d intervention period. Consumption of NO3- had no effect on resting systolic and diastolic BP. NO3- consumption did not improve indexes of central and peripheral cardiac function responses during cardiopulmonary exercise testing. Dietary NO3- supplementation did not modify biomarkers of inflammation, oxidative stress and endothelial integrity. This study does not support the short-term benefits of dietary NO3- supplementation on physiological and biochemical markers of vascular health in older healthy adults. Graphical Abstract

Jumping depends on impulse not power

We read with interest the manuscript by Russell, Sparkes, Northeast & Kilduff (2015) and noted their use of power to characterise performance in jumping. Such use is widespread in sport and exercise science, but it is also incorrect. The success of either a vertical or horizontal jump is determined by velocity at take-off. From Newton’s second law of motion outlined in Principia that was published in 1687, this velocity is determined by the preceding impulse generated by an athlete. In the context of jumping, misuse of the construct power was highlighted several decades ago by Adamson and Whitney (1971). Because velocity is a vector quantity, it possesses both magnitude and direction. Newton’s second law is expressed as the impulse–momentum relationship and the relationship allows precise identification of velocity at departure. Themathematical link that identifies this velocity is irrefutable. Adamson and Whitney’s (1971) objections were followed by others (Knudson, 2009; Cronin & Sleivert, 2005; Knuttgen, 1978; Rodgers & Cavanagh, 1984; Winter, 2005; Winter & Fowler, 2009) to clarify misconceptions. In spite of this, authors often continue to associate and at worst attempt to explain jumping performance in scientific literature by means of “power” as if it were a clearly defined key performance variable (Knudson, 2009). The definition of power from classical (Newtonian) mechanics is the rate of doing work (J · s) (Rodgers &Cavanagh, 1984). It is problematic to consider short-duration, discrete projectile activities as “power” events and hence incorrect to extend assessments of power to describe and explain performance in impulsive activities such as jumping. When a jump is performed on a force platform, a key metric is the integral of force and time, i.e. the area under the force–time curve. Information from this curve can be used beguilingly to provide a velocity–time profile of the body’s centre of mass. At this point it is worth considering that power is also frequently but erroneously calculated as products of force (F) and velocity (v),

Effects of Creatine and Sodium Bicarbonate Coingestion on Multiple Indices of Mechanical Power Output During Repeated Wingate Tests in Trained Men

This study investigated the effects of creatine and sodium bicarbonate coingestion on mechanical power during repeated sprints. Nine well-trained men (age = 21.6 ± 0.9 yr, stature = 1.82 ± 0.05 m, body mass = 80.1 ±12.8 kg) participated in a double-blind, placebo-controlled, counterbalanced, crossover study using six 10-s repeated Wingate tests. Participants ingested either a placebo (0.5 g·kg(-1) of maltodextrin), 20 g·d(-1) of creatine monohydrate + placebo, 0.3 g·kg(-1) of sodium bicarbonate + placebo, or coingestion + placebo for 7 days, with a 7-day washout between conditions. Participants were randomized into two groups with a differential counterbalanced order. Creatine conditions were ordered first and last. Indices of mechanical power output (W), total work (J) and fatigue index (W·s(-1)) were measured during each test and analyzed using the magnitude of differences between groups in relation to the smallest worthwhile change in performance. Compared with placebo, both creatine (effect size (ES) = 0.37-0.83) and sodium bicarbonate (ES = 0.22-0.46) reported meaningful improvements on indices of mechanical power output. Coingestion provided small meaningful improvements on indices of mechanical power output (W) compared with sodium bicarbonate (ES = 0.28-0.41), but not when compared with creatine (ES = -0.21-0.14). Coingestion provided a small meaningful improvement in total work (J; ES = 0.24) compared with creatine. Fatigue index (W·s(-1)) was impaired in all conditions compared with placebo. In conclusion, there was no meaningful additive effect of creatine and sodium bicarbonate coingestion on mechanical power during repeated sprints.

Physiology and Risk Management of Cold Exposure

When combined with extreme environmental conditions extreme sport challenges and often pushes physiological capacities to their regulatory limit, impairing performance and increasing the risk of serious medical conditions. Cold environmental temperatures associated with water and air exposure are of particular concern as hypothermia and cold injury can occur rapidly and without warning. Despite controlled endothermy that utilises several integrated thermoregulatory mechanisms, human body temperature is constrained by environmental biophysics. In cold environments rapid heat exchange can occur if metabolic heat production is insufficient to maintain thermal balance, or because of limited protection from extreme conditions. Declining body temperatures are associated with reduced dexterity, shivering, poor muscle co-ordination and force production, amnesia and cardiovascular strain that might challenge human survival let alone performance. The occurrence of cold injury can be alleviated with the implementation of risk management strategies that are designed to assess environmental conditions, location, protection and metabolic heat production of the event. The aim of this chapter is to highlight the risks associated with cold environments by presenting pertinent research, physiological responses and applied practice relevant to sport medics, athletes and coaches challenges.