The role of pulse transit time as an index of arterial stiffness during exercise

The aim of the present study was to investigate, whether pulse transit time (PTT), a popular index of arterial stiffness at rest, can be also used as such, during steady state exercise. For this purpose, twelve male volunteers exercised on a cycle ergometer for 70 min on three separate occasions whereas, cycling cadence and workload were manipulated in order to produce diverse cardiorespiratory responses. PTT, blood pressure, cardiac output and respiratory frequency were measured during exercise. Resistance to systole and total peripheral resistance were calculated by the ratio of systolic pressure, and mean arterial pressure over cardiac output, respectively. All subjects across all conditions, showed a negative linear correlation (P < 0.01) between changes in PTT and systolic pressure (SP) (r = -0.66), changes in cardiac output (r = -0.76), and respiratory frequency (r = -0.40), whereas PTT was positively correlated (P < 0.05) with total peripheral resistance (r = 0.31), the SP to cardiac output ratio (r = 0.30) and plasma volume changes (r = 0.29). However, forward stepwise multiple regression analysis revealed that 71% (P < 0.001) of PTT changes from rest (ΔPTT) variability was attributed to changes in cardiac output, SP and SP to cardiac output ratio. In the same model, total peripheral resistance did not exert significant influence on ΔPTT variability. In conclusion, PTT is a reflection not only of SP but also of cardiac output changes per se and in combination with cardiac output (SP to cardiac output ratio) and should not be used as a pure marker of arterial stiffness under marked exercise cardiovascular and respiratory perturbations. © Springer Science+Business Media, LLC 2009

Five repeated maximal efforts of apneas increase the time to exhaustion in subsequent high-intensity exercise

Ten subjects were tested on a cycle ergometer to exhaustion with intensity corresponding to 150 % of their peak power output (TF150) under three conditions [C: base line measurement; PRE: after five repeated breath hold maneuvers (BH); and POST: after 5BH, preceded by two weeks of BH training]. Respiratory and blood measurements were carried out. Upon cessation of 5BH, subjects compared to C condition started TF150 with reduced arterialized blood pH (C:7.428±0.023, PRE:7.419±0.016, POST:7.398±0.021) and elevated bicarbonate concentration (mmol/l), ventilation (l/min) and oxygen uptake (ml/min) (C:28.4±1.5, PRE:29.9±1.2, POST:30.0±1.8; C:10.4±2.5, PRE:13.3±3.3, POST:15.6±5.6; C:333.0±113.8, PRE:550.1±131.1, POST:585.1±192.8, respectively). After TF150, subjects had significantly reduced pH and elevated ventilation, and oxygen uptake in PRE and POST, in comparison to the C condition. TF150 (sec) significantly improved after 5BH without being further affected by BH training (C:44.8±8.1, PRE:49.2±4.8, POST:49.3±8.2). Priming breath holds prior to middle-distance racing may improve performance. © 2021 Elsevier B.V

Cardiovascular drift and cerebral and muscle tissue oxygenation during prolonged cycling at different pedalling cadences

We hypothesized that a faster cycling cadence could exaggerate cardiovascular drift and affect muscle and cerebral blood volume and oxygenation. Twelve healthy males (mean age, 23.4 ± 3.8 years) performed cycle ergometry for 90 min on 2 separate occasions, with pedalling frequencies of 40 and 80 r·min -1, at individual workloads corresponding to 60% of their peak oxygen consumption. The main measured variables were heart rate, ventilation, cardiac output, electromyographic activity of the vastus lateralis, and regional muscle and cerebral blood volume and oxygenation. Cardiovascular drift developed at both cadences, but it was more pronounced at the faster than at the slower cadence, as indicated by the drop in cardiac output by 1.0 ± 0.2 L·min -1, the decline in stroke volume by 9 ± 3 mL·beat -1, and the increase in heart rate by 9 ± 1 beats·min -1 at 80 r·min -1. At the faster cadence, minute ventilation was higher by 5.0 ± 0.5 L·min -1, and end-tidal CO 2 pressure was lower by 2.0 ± 0.1 torr. Although higher electromyographic activity in the vastus lateralis was recorded at 80 r·min -1, muscle blood volume did not increase at this cadence, as it did at 40 r·min -1. In addition, muscle oxygenation was no different between cadences. In contrast, cerebral regional blood volume and oxygenation at 80 r·min -1 were not as high as at 40 r·min -1 (p < 0.05). Faster cycling cadence exaggerates cardiovascular drift and seems to influence muscle and cerebral blood volume and cerebral oxygenation, without muscle oxygenation being radically affected

The effect of interval training combined with thigh cuffs pressure on maximal and submaximal exercise performance

The purpose of the study was to investigate the effect of interval training combined with a thigh cuffs pressure of +90mmHg on maximal and submaximal cycling performance. Twenty untrained individuals were assigned either to a control (CON) or to an experimental (CUFF) training group. Both groups trained 3days per week for 6weeks at the same relative intensity; each training session consisted of 2-min work bout at 90% of : 2-min active recovery bout at 50% of An incremental exercise test to exhaustion, a 6-min constant-power test at 80% of (Sub 80) and a maximal constant-power test to exhaustion (TF 150) were performed pre- and post-training. Despite the unchanged , both groups significantly increased peak power output (CON: ~12%, CUFF: ~20%) that was accompanied by higher deoxygenation (ΔStO 2) measured with near-infrared muscle spectroscopy. These changes were more pronounced in the CUFF group. Moreover, both groups reduced during the Sub 80 test without concomitant changes in ΔStO 2. TF 150 was enhanced in both groups. Thus, an interval exercise training protocol under moderate restricted blood flow conditions does not provide any additive effect on maximal and submaximal cycling performance. However, it seems to induce peripheral muscular adaptations, despite the lower absolute training intensity. © 2011 Scandinavian Society of Clinical Physiology and Nuclear Medicine

Oxygen saturation in the triceps brachii muscle during an arm wingate test: The role of training and power output

The purpose of this study was to investigate the role of training and power output on muscle oxygen desaturation during and resaturation after an arm Wingate test (WAnT). Two groups of subjects were studied; the first group consisted of nine athletes participating in upper arm anaerobic sports and the second group of 11 university students. As a consequence, the group of athletes (HP) produced higher peak and mean power output (p < 0.01) than the group of university students (LP). Muscle oxygenation status was evaluated by using near infrared spectroscopy at the triceps brachii. The HP group exhibited 17.6 ± 8.0% less muscle oxygen desaturation than the LP group (p < 0.05) but similar muscle total hemoglobin during exercise and faster (p < 0.05) muscle oxygen resaturation during recovery ( τ= 12.4 ± 5.2 sec in HP vs. τ= 24.2 ± 11.0 sec in LP). These results indicate that the HP group exhibits less muscle desaturation during an arm WAnT and has a faster resaturation rate, probably attributed to differences in muscle mass, muscle fiber recruitment capability, and ATP production through anaerobic pathways

Somatic and physical traits affecting sprint swimming performance in young swimmers

The aim of this study was to examine the relationship between anthropometry, physical capacity, and sprint swimming performance in swimmers of both genders aged 12-14 years old. Anthropometric characteristics (body height and mass, total upper extremity, hand and foot lengths, chest circumference, certain body breadths, and skinfolds), as well as leg explosiveness (horizontal jump) and arm strength (handgrip strength test) were evaluated in 263 competitive swimmers (178 boys and 85 girls) aged 12-14 years. Skeletal age was assessed with the Tanner-Whitehouse method. All variables, except for the ankle and shoulder flexibility as well as the skeletal age, correlated with 100m freestyle performance in boys (r = - 0.46 to - 0.73, p < 0.01). Using a split-sample approach, upper extremity length, horizontal jump, and grip strength were detected as significant predictors of 100m freestyle performance in boys (R 2 = 0.59, p < 0.01). In girls, body height, upper extremity and hand length, shoulder flexibility, and horizontal jump were all significantly related to 100m freestyle time (r = - 0.22 to - 0.31, p < 0.05) but the degree of association was markedly lower than in boys. In addition, only 17% of the variance in performance was explained by a combination of body height, hand length, and horizontal jump in girls. These results suggest that 100m freestyle performance can be partially explained by anthropometry and physical capacity tests in young swimmers. The contribution of these factors to sprint swimming performance is different in boys and girls and this requires further research. These findings could be used for male young swimmers' selection. © Georg Thieme Verlag KG

Forearm-finger skin temperature gradient as an index of cutaneous perfusion during steady-state exercise

The purpose of this study was to examine whether the forearm-finger skin temperature gradient (Tforearm-finger), an index of vasomotor tone during resting conditions, can also be used during steady-state exercise. Twelve healthy men performed three cycling trials at an intensity of ~60% of their maximal oxygen uptake for 75 min separated by at least 48 h. During exercise, forearm skin blood flow (BFF) was measured with a laser-Doppler flowmeter, and finger skin blood flow (PPG) was recorded from the left index fingertip using a pulse plethysmogram. Tforearm-finger of the left arm was calculated from the values derived by two thermistors placed on the radial side of the forearm and on the tip of the middle finger. During exercise, PPG and BFF increased (P<0·001), and Tforearm-finger decreased (P<0·001) from their resting values, indicating a peripheral vasodilatation. There was a significant correlation between Tforearm-finger and both PPG (r = -0·68; P<0·001) and BFF (r = -0·50; P<0·001). It is concluded that Tforearm-finger is a valid qualitative index of cutaneous vasomotor tone during steady-state exercise. © 2013 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd

Cardiovascular drift in trained paraplegic and able-bodied individuals during prolonged wheelchair exercise: Effect of fluid replacement

The progressive heart rate (HR) increase and stroke volume (SV) decline during prolonged constant-load leg exercise signifies cardiovascular drift (CVdrift); fluid replacement is known to minimize this phenomenon. Like their able-bodied counterparts (AB), paraplegic athletes undergo prolonged exercise during training and competition, which could result in CVdrift. The aim of this study is to address the role of rehydration on preventing CVdrift in spinal cord injured (SCI) paraplegic athletes. Eight SCI athletes with an injury level between C7 and T6 and 9 AB subjects performed 60-min constant-load exercise on a wheelchair ergometer in a thermo-neutral environment. No fluid was taken in 1 trial, whereas 85% of sweat losses were replaced by drinking water in another trial. Cardic output (CO), SV, HR, and oral temperature (Tor) were determined during exercise. Prolonged exercise resulted in similar HR (18 beats·min-1 for AB and 12 beats·min-1 for SCI) and Tor (0.63 °C for AB and 0.71 °C for SCI) elevation and SV decline (-8.5 mL·beat-1 for AB and -5.5 mL·beat-1 for SCI), whereas CO remained unchanged. Water intake restrained the exercise-induced hyperthermia and resulted in smaller SV decline (-4.0 mL for AB and -3.0 mL for SCI, p < 0.01). In conclusion, CVdrift was similar in SCI and AB subjects during prolonged wheelchair exercise. Likewise, the beneficial effects of hydration in both groups were analogous

The effect of menthol application to the skin on sweating rate response during exercise in swimmers and controls

We tested the hypothesis that menthol application would reduce the magnitude and initiation of sweating via excitation of cold-sensitive afferent pathways and concurrently via a cross-inhibition of heat loss pathways in acclimatized (swimmers, SW) and non acclimatized (control, CON) subjects in cool water. It was expected this effect to be exaggerated in SW subjects. Eight SW and eight CON subjects cycled at 60% of their V̇O2max, as long as to reach 38°C in rectal temperature (Tre), without or with (4.6 g per 100 ml of water) all-body application of menthol sediment. Heart rate (HR), Tre, sweating rate (SwR), the proximal-distal skin temperature gradient (TSk f-f), and oxygen consumption (V̇O2) were measured continuously. V̇O2 and HR were similar between groups and conditions. Menthol increased TSkf-f, Tre threshold for SwR [+0.32 (0.01)°C] and Tre gain, while menthol reduced exercise time by 8.1 (4.1) min. SW group showed higher changes in Tre threshold for SwR [+0.50 (0.01)°C for SW vs. +0.13 (0.03)°C for CON], higher Tre gain, lower time for Tre increase and shorter exercise time [-10.7 (7) min for SW vs. -4.9 (4) min for CON] in menthol condition. Upon exercise initiation, previously applied menthol on the skin seems to induce vasoconstriction, results in a delayed sweating, which in turn affects the rectal temperature. Acclimatized subjects showed higher delay in SwR and earlier rise in Tre, which most probably is due to the inter-group differences in cold receptors activity. © Springer-Verlag 2010