The effects of prior postactivation potentiation on 4 km cycling time trial performance

The aim of this study was to examine the effects of post-activation potentiation (PAP) on performance and physiological measures during endurance cycling. Eleven well trained male endurance cyclists (mean ± SD; 32.7 ± 10.3 yr; 70.7 ± 7.2 kg; VO2max 65.3 ± 5.3 ml·kg-1·min-1) performed two 4 km cycling time trials on separate days following 5 minutes recovery after a) a moderate intensity cycling warm-up at 60% of VO2peak for 6.5 minutes (CONTCOND), and b) a PAP-inducing cycling warm-up (PAPCOND) consisting of 5 minutes at 60% of VO2peak then 3 x 10 s at 70% of peak power interspersed with 30 s recovery, in a counterbalanced design. Before the start of the time trial blood lactate was significantly elevated following PAP-inducement compared to the moderate warm-up (4.88 ± 1.36 mM·L-1 vs 1.14m ± 0.26 mM·L-1). A non-significant possibly small improvement in completion time (1.7 ± 3.5 s, P = 0.17) and a non-significant increase in power (5.1 ± 10.5 W, P = 0.16) were attributed to PAPCOND. Following PAPCOND oxygen uptake (VO2) was elevated by 1.44 ± 1.65 ml·kg-1·min-1 (P = 0.02) and respiratory exchange ratio (RER) was decreased by 0.05 ± 0.02 (P < 0.01) compared to CONTCOND. All differences were greatest in the first 1500 m. A PAP-inducing warm-up leads to small performance improvements in endurance cycling that are associated with elevated blood lactate and increased VO2. These performance improvements are most evident in the early stages so would be of greatest benefit in short endurance cycle races

The effects of a cycling warm-up including high-intensity heavy-resistance conditioning contractions on subsequent 4 km time trial performance

Prior exercise has been shown to improve subsequent performance via different mechanisms. Sport-specific conditioning contractions can be used to exploit the 'post-activation potentiation' (PAP) phenomenon to enhance performance although this has rarely been investigated in short endurance events. The aim of this study was to compare a cycling warm-up with PAP-inducing conditioning contractions (CW) with a moderate intensity warm-up (MW) on performance and physiological outcomes of 4 km time trial. Ten well-trained male endurance cyclists (V[Combining Dot Above]O2max 65.3 +/- 5.6 ml[middle dot]kg-1[middle dot]min-1) performed two 4 km cycling time trials following a 5-minute recovery after a warm-up at 60% of V[Combining Dot Above]O2max for 6.5-minutes (MW), and a warm-up with conditioning contractions (CW) consisting of 5 minutes at 60% of V[Combining Dot Above]O2max then 3 x 10-seconds at 70% of peak power interspersed with 30-seconds recovery. Blood lactate concentrations were measured before and after time trial. Expired gases were analysed along with time, power output (PO), and peak forces over each 500 m split. Following CW, mean completion time was reduced (1.7 +/- 3.5 s p > 0.05), PO increased (5.1 +/- 10.5 W p > 0.05) as did peak force per pedal stroke (5.7 +/- 11 N p > 0.05) when compared to MW. V[Combining Dot Above]O2 increased (1.4 +/- 1.6 ml[middle dot]kg-1[middle dot]min-1 p < 0.05) following CW, whilst RER decreased (0.05 +/- 0.02 p < 0.05). Physiological and performance differences following CW were greatest over the first 1500 m of the trials. The results suggest a PAP-inducing warm-up alters V[Combining Dot Above]O2 kinetics and can lead to performance improvements in short endurance cycling but work and recovery durations should be optimised for each athlete

Bi-exponential modelling of W ′ reconstitution kinetics in trained cyclists

From Springer Nature via Jisc Publications RouterHistory: received 2021-06-21, accepted 2021-12-10, registration 2021-12-11, pub-electronic 2021-12-18, online 2021-12-18, pub-print 2022-03Publication status: PublishedAbstract: Purpose: The aim of this study was to investigate the individual W′ reconstitution kinetics of trained cyclists following repeated bouts of incremental ramp exercise, and to determine an optimal mathematical model to describe W′ reconstitution. Methods: Ten trained cyclists (age 41 ± 10 years; mass 73.4 ± 9.9 kg; V˙O2max 58.6 ± 7.1 mL kg min−1) completed three incremental ramps (20 W min−1) to the limit of tolerance with varying recovery durations (15–360 s) on 5–9 occasions. W′ reconstitution was measured following the first and second recovery periods against which mono-exponential and bi-exponential models were compared with adjusted R2 and bias-corrected Akaike information criterion (AICc). Results: A bi-exponential model outperformed the mono-exponential model of W′ reconstitution (AICc 30.2 versus 72.2), fitting group mean data well (adjR2 = 0.999) for the first recovery when optimised with parameters of fast component (FC) amplitude = 50.67%; slow component (SC) amplitude = 49.33%; time constant (τ)FC = 21.5 s; τSC = 388 s. Following the second recovery, W′ reconstitution reduced by 9.1 ± 7.3%, at 180 s and 8.2 ± 9.8% at 240 s resulting in an increase in the modelled τSC to 716 s with τFC unchanged. Individual bi-exponential models also fit well (adjR2 = 0.978 ± 0.017) with large individual parameter variations (FC amplitude 47.7 ± 17.8%; first recovery: (τ)FC = 22.0 ± 11.8 s; (τ)SC = 377 ± 100 s; second recovery: (τ)FC = 16.3.0 ± 6.6 s; (τ)SC = 549 ± 226 s). Conclusions: W′ reconstitution kinetics were best described by a bi-exponential model consisting of distinct fast and slow phases. The amplitudes of the FC and SC remained unchanged with repeated bouts, with a slowing of W′ reconstitution confined to an increase in the time constant of the slow component

Physiological and anthropometric determinants of critical power, W ′ and the reconstitution of W ′ in trained and untrained male cyclists

From Springer Nature via Jisc Publications RouterHistory: received 2020-01-17, accepted 2020-07-31, registration 2020-08-01, pub-electronic 2020-08-09, online 2020-08-09, pub-print 2020-11Publication status: PublishedAbstract: Purpose: This study examined the relationship of physiological and anthropometric characteristics with parameters of the critical power (CP) model, and in particular the reconstitution of W′ following successive bouts of maximal exercise, amongst trained and untrained cyclists. Methods: Twenty male adults (trained nine; untrained 11; age 39 ± 15 year; mass 74.7 ± 8.7 kg; V̇O2max 58.0 ± 8.7 mL kg−1 min−1) completed three incremental ramps (20 W min−1) to exhaustion interspersed with 2-min recoveries. Pearson’s correlation coefficients were used to assess relationships for W′ reconstitution after the first recovery (W′rec1), the delta in W′ reconstituted between recoveries (∆W′rec), CP and W′. Results: CP was strongly related to V̇O2max for both trained (r = 0.82) and untrained participants (r = 0.71), whereas W′ was related to V̇O2max when both groups were considered together (r = 0.54). W′rec1 was strongly related to V̇O2max for the trained (r = 0.81) but not untrained (r = 0.18); similarly, ∆W′rec was strongly related to V̇O2max (r = − 0.85) and CP (r = − 0.71) in the trained group only. Conclusions: Notable physiological relationships between parameters of aerobic fitness and the measurements of W′ reconstitution were observed, which differed among groups. The amount of W′ reconstitution and the maintenance of W′ reconstitution that occurred with repeated bouts of maximal exercise were found to be related to key measures of aerobic fitness such as CP and V̇O2max. This data demonstrates that trained cyclists wishing to improve their rate of W′ reconstitution following repeated efforts should focus training on improving key aspects of aerobic fitness such as V̇O2max and CP

The Reconstitution and Modelling of the Work Capacity Above Critical Power Following Severe Intensity Cycling

The two-parameter critical power model comprising critical power (CP) and W′ is well accepted as a mathematical model representing exercise in the severe intensity domain. CP represents the maximum work rate derived from aerobic metabolism and W′ the fixed capacity of work above CP. However, within competitive cycle sport few races are performed exclusively within this domain, instead stochastic efforts where W′ is repeatedly depleted and reconstituted typify race demands. Relatively little is known about the reconstitution mechanisms and kinetics of W′ hence the initial aims of this thesis were to develop a reliable method of assessing W′ reconstruction and evaluate likely underlying physiological contributors to the rate of W′ reconstitution. Thereafter, the aim was to develop a dynamic model of W′ reconstitution and depletion which could contribute to race planning and tactics leading to improved sporting performance. A repeated ramp test developed for Study 1 to measure the amount of W′ reconstituted following its full depletion was found to produce reliable results for 2-min recoveries at 50 W (ICC ≥ 0.859; TE ≤ 559 J; CV ≤ 9.2%). A slowing of W′ reconstitution following the repeated bout was evident in this and all subsequent studies. Study 2 found that W′ reconstitution after 2-min recovery was related to measures of aerobic fitness such as V̇O2max (r = 0.81) and CP (r = 0.52) in trained cyclists, whilst the reconstitution of W′ was more related to fat mass in untrained participants (r = -0.70). Studies 1 & 2 also demonstrated existing mono-exponential models of W′ balance did not fit the results obtained after 2-min recovery periods. Therefore, Study 3 compared existing mono-exponential models to a bi-exponential model, finding the latter a much superior fit (AICc bi-exponential: 72.2 versus bi-exponential: 30.2) of the temporal profile of W′ reconstitution of trained cyclists. The resultant model demonstrated that W′ comprised distinct fast and slow components that were unrelated to each other. Study 4 assessed the likelihood of a minimum recovery power output beyond which no further improvement in the rate of W′ reconstitution was apparent. Study 5 investigated the effects of different recovery intensities on W′ reconstitution. Fitting the results of the different recovery intensities into the bi-exponential framework of Study 3 allowed a full dynamic model of W′ reconstitution and depletion to be built allowing for both duration and intensity. The model can be customised to an athlete using the known parameters of CP and W′ together with a single additional test session including a 4-min recovery at 85% of CP. The model can be applied in real time for use by cyclists in competition to aid tactical decision making and optimising race performance

Effect of varying recovery intensities on power outputs during severe intensity intervals in trained cyclists during the Covid-19 pandemic.

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record will soon be available online.Purpose: The study aimed to investigate the effects of different recovery intensities on the power outputs of repeated severe intensity intervals and the implications for W′ reconstitution in trained cyclists. Methods: 18 trained cyclists (FTP 258.0 ± 42.7 W; weekly training 8.6 ± 1.7 h∙week-1) familiar with interval training, use of the Zwift® platform throughout the Covid-19 pandemic and previously established FTP (95% of mean power output from a 20-min test), performed 5 x 3-min severe intensity efforts interspersed with 2-min recoveries. Recovery intensities were: 50 W (LOW), 50% of functional threshold power (MOD), and self-selected power output (SELF). Results: Whilst power outputs declined as the session progressed, mean power outputs during the severe intervals across the conditions were not different to each other (LOW 300.1 ± 48.1 W; MOD: 296.9 ± 50.4 W; SELF: 298.8 ± 53.3 W) despite the different recovery conditions. Mean power outputs of the self-selected recovery periods were 121.7 ± 26.2 W. However, intensity varied during the self-selected recovery periods, with values in the last 15-s being greater than the first 15-s (p <0.001) and decreasing throughout the session (128.7 ± 25.4 W to 113.9 ± 29.3 W). Conclusions: Reducing recovery intensities below 50% of FTP failed to enhance subsequent severe intensity intervals, suggesting a lower limit for optimal W′ reconstitution had been reached. As self-selected recoveries were seen to adapt in order to maintain the severe intensity power output as the session progressed, adopting such a strategy might be preferential for interval training sessions

A dynamic model of the bi-exponential reconstitution and expenditure of W′ in trained cyclists

From Crossref journal articles via Jisc Publications RouterHistory: epub 2023-07-20, issued 2023-07-20, published 2023-07-20Publication status: Publishe

Bi-exponential modelling of W' reconstitution kinetics in trained cyclists

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s00421-021-04874-3Purpose The aim of this study was to investigate the individual W′ reconstitution kinetics of trained cyclists following repeated bouts of incremental ramp exercise, and to determine an optimal mathematical model to describe W′ reconstitution. Methods Ten trained cyclists (age 41 ± 10 years; mass 73.4 ± 9.9 kg; V˙O2max 58.6 ± 7.1 mL kg min−1) completed three incremental ramps (20 W min−1) to the limit of tolerance with varying recovery durations (15–360 s) on 5–9 occasions. W′ reconstitution was measured following the first and second recovery periods against which mono-exponential and bi-exponential models were compared with adjusted R2 and bias-corrected Akaike information criterion (AICc). Results A bi-exponential model outperformed the mono-exponential model of W′ reconstitution (AICc 30.2 versus 72.2), fitting group mean data well (adjR2 = 0.999) for the first recovery when optimised with parameters of fast component (FC) amplitude = 50.67%; slow component (SC) amplitude = 49.33%; time constant (τ)FC = 21.5 s; τSC = 388 s. Following the second recovery, W′ reconstitution reduced by 9.1 ± 7.3%, at 180 s and 8.2 ± 9.8% at 240 s resulting in an increase in the modelled τSC to 716 s with τFC unchanged. Individual bi-exponential models also fit well (adjR2 = 0.978 ± 0.017) with large individual parameter variations (FC amplitude 47.7 ± 17.8%; first recovery: (τ)FC = 22.0 ± 11.8 s; (τ)SC = 377 ± 100 s; second recovery: (τ)FC = 16.3.0 ± 6.6 s; (τ)SC = 549 ± 226 s). Conclusions W′ reconstitution kinetics were best described by a bi-exponential model consisting of distinct fast and slow phases. The amplitudes of the FC and SC remained unchanged with repeated bouts, with a slowing of W′ reconstitution confined to an increase in the time constant of the slow component

The Physicochemistry of Capped Nanosilver Predicts Its Biological Activity in Rat Brain Endothelial Cells (RBEC4)

The “capping” or coating of nanosilver (nanoAg) extends its potency by limiting its oxidation and aggregation and stabilizing its size and shape. The ability of such coated nanoAg to alter the permeability and activate oxidative stress pathways in rat brain endothelial cells (RBEC4) was examined in the present study. The aggregate size and zeta potential of nanoAg with different sizes (10 and 75 nm) and coatings (PVP and citrate) were measured in cell culture media. Results indicated that both PVP-coated nanoAg were less electronegative than their citrate-coated counterparts over all exposure times, but only the PVP-coated 10 nm particles retained their initial electronegativity over all exposure times. In addition, only the PVP-coated particles retained their initial sizes throughout the 3 h measurement. PVP-coated 10 nm nanoAg selectively altered the permeability of RBEC4 monolayers within a 15 min exposure, although high resolution microscopy indicated that all coated nanoAg distributed throughout the cell’s cytoplasm within the 3 h exposure. Reporter genes for AP-1 and NRF2/ARE, transfected into RBEC4, were selectively stimulated by the PVP-coated 10 nm nanoAg. Global gene arrays indicated that only PVP-coated nanoAg significantly altered gene expressions in the RBEC4, and those altered by 10 nm PVP-coated nanoAg were qualitatively similar but quantitatively much higher than those of its 75 nm counterpart. IPA and DAVID analyses indicated that the altered pathways affected by both PVP-coated nanoAg were primarily associated with a NRF2-mediated oxidative stress response, endocytosis, and bioenergetics. Together, these data suggest that the physicochemical features of surface coating aggregate size and surface charge contribute to capped nanoAg’s permeability and oxidative stress responses in RBEC4

The Physicochemistry of Capped Nanosilver Predicts Its Biological Activity in Rat Brain Endothelial Cells (RBEC4)

The “capping” or coating of nanosilver (nanoAg) extends its potency by limiting its oxidation and aggregation and stabilizing its size and shape. The ability of such coated nanoAg to alter the permeability and activate oxidative stress pathways in rat brain endothelial cells (RBEC4) was examined in the present study. The aggregate size and zeta potential of nanoAg with different sizes (10 and 75 nm) and coatings (PVP and citrate) were measured in cell culture media. Results indicated that both PVP-coated nanoAg were less electronegative than their citrate-coated counterparts over all exposure times, but only the PVP-coated 10 nm particles retained their initial electronegativity over all exposure times. In addition, only the PVP-coated particles retained their initial sizes throughout the 3 h measurement. PVP-coated 10 nm nanoAg selectively altered the permeability of RBEC4 monolayers within a 15 min exposure, although high resolution microscopy indicated that all coated nanoAg distributed throughout the cell’s cytoplasm within the 3 h exposure. Reporter genes for AP-1 and NRF2/ARE, transfected into RBEC4, were selectively stimulated by the PVP-coated 10 nm nanoAg. Global gene arrays indicated that only PVP-coated nanoAg significantly altered gene expressions in the RBEC4, and those altered by 10 nm PVP-coated nanoAg were qualitatively similar but quantitatively much higher than those of its 75 nm counterpart. IPA and DAVID analyses indicated that the altered pathways affected by both PVP-coated nanoAg were primarily associated with a NRF2-mediated oxidative stress response, endocytosis, and bioenergetics. Together, these data suggest that the physicochemical features of surface coating aggregate size and surface charge contribute to capped nanoAg’s permeability and oxidative stress responses in RBEC4