Effects of Flywheel Strength Training on the Running Economy of Recreational Endurance Runners.

Festa, L, Tarperi, C, Skroce, K, Boccia, G, Lippi, G, La Torre, A, and Schena, F. Effects of flywheel strength training on the running economy of recreational endurance runners. J Strength Cond Res 33(3): 684-690, 2019-Running economy (RE) has been defined as the most important determining factor in endurance performance in both elite and recreational runners. The purpose of this study was to evaluate the effect of flywheel strength training (FST) and high-intensity training (HIT) protocols on RE and strength parameters in a group of recreational runners. Twenty-nine recreational runners were recruited to take part in the study and were randomly assigned to FST (n = 9; 44.5 ± 6.0 years; V[Combining Dot Above]O2max 48.8 ± 5.2 ml·min·kg), HIT (n = 9; 42.2 ± 8.6 years; V[Combining Dot Above]O2max 50.3 ± 3.7 ml·min·kg), or low-intensity training (LIT) (n = 11; 45.4 ± 8.0 years; V[Combining Dot Above]O2max 50.2 ± 6.8 ml min kg) groups. Before and after 8 weeks of an experimental period, maximal oxygen uptake (V[Combining Dot Above]O2max), ventilatory thresholds (VTs), maximal dynamic force (1 repetition maximum [1RM]), and anthropometric data were evaluated. The FST group showed significant increases (p < 0.05) in 1RM and RE. No differences were found in the other groups. Significative changes are found for all groups on average speed on 2 and 10 km (p < 0.05). Anthropometric data were unchanged after the training period. The results of this study indicate that in recreational runners, FST seems able to obtain improvements in RE and neuromuscular adaptation.

Prothrombotic State Induced by Middle-Distance Endurance Exercise in Middle-Aged Athletes.

Since the impact of possible prothrombotic factors on blood coagulation resulting from exercise remains elusive, this study investigated the acute effects of middle-distance endurance running on blood coagulation parameters in middle-aged athletes. The study population consisted of 33 male endurance runners who were engaged in a 21.1 km run under competitive conditions. Blood samples were collected before the run, immediately after the run, and 3 hours after run completion. Samples were assessed for activated partial thromboplastin time (APTT), prothrombin time (PT), fibrinogen, D-dimer, factor VIII (FVIII), von Willebrand factor antigen (VWF:Ag), endogenous thrombin potential (area under the curve of thrombin generation [TGA-AUC]), and peak thrombin generation (TGA-PK). Post-run variations were expressed as delta (Δ). At baseline, APTT was found to be significantly associated with ABO blood group, VWF:Ag, and FVIII; fibrinogen with age; VWF:Ag with BMI, training regimen, and ABO blood group; APTT with FVIII; FVIII with VWF:Ag and ABO blood group; APTT with VWF:Ag; and TGA-PK with ABO blood group, PT, and TGA-AUC. Immediately after the run, statistically significant increases were observed for PT, D-dimer, VWF:Ag, and FVIII, while statistically significant reductions could be observed for APTT, TGA-AUC, and TGA-PK. Fibrinogen values remained unchanged. Significant correlations were observed between Δ VWF:Ag and Δ FVIII, Δ APTT and Δ VWF:Ag, Δ APTT and Δ FVIII, Δ TGA-AUC and Δ TGA-PK, and between Δ D-dimer and Δ TGA-AUC and Δ TGA-PK. No Δ variation was associated with running time. The results of this study seemingly suggest that middle-distance competitive running may evoke several prothrombotic changes in blood coagulation.

The effect of leg preference on mechanical efficiency during single-leg extension exercise.

To investigate how leg preference affects net efficiency (ηnet), we examined central and peripheral hemodynamics, muscle fiber type, activation and force of preferred (PL) and nonpreferred (NPL) leg. Our hypothesis was that PL greater efficiency could be explained by adaptations and interactions between central, peripheral factors, and force. Fifteen young participants performed single-leg extension exercise at absolute (35 W) and relative [50% peak power-output (Wpeak)] workloads with PL and NPL. Oxygen uptake, photoplethysmography, Doppler ultrasound, near-infrared-spectroscopy deoxyhemoglobin [HHb], integrated electromyography (iEMG), maximal isometric force (MVC), rate of force development (RFD50-100), and muscle biopsies of both vastus lateralis were studied to assess central and peripheral determinants of ηnet. During exercise executed at 35 W, ηnet was 17.5 ± 5.1% and 11.9 ± 2.1% (P < 0.01) in PL and NPL respectively, whereas during exercise at the 50% of Wpeak was in PL = 18.1 ± 5.1% and in NPL = 12.5 ± 1.9 (P < 0.01). The only parameter correlated with ηnet was iEMG, which showed an inverse correlation for absolute (r = -0.83 and -0.69 for PL and NPL) and relative workloads (r = -0.92 and -0.79 for PL and NPL). MVC and RFD50-100 were higher in PL than in NPL but not correlated to ηnet. This study identified a critical role of leg preference in the efficiency during single-leg extension exercise. The whole spectrum of the central and peripheral, circulatory, and muscular determinants of ηnet did not explain the difference between PL and NPL efficiency. Therefore, the lower muscle activation exhibited by the PL is likely the primary determinant of this physiological phenomenon.NEW & NOTEWORTHY This study examined the impact of leg preference on efficiency during single-leg exercise. The results revealed lower efficiency of the nonpreferred leg during exercises performed at absolute and relative workloads. Central (cardiac output) and peripheral (fiber typing) determinants of efficiency did not explain the difference between the legs. However, the lower muscle activation of the preferred leg that was inversely correlated with efficiency is likely the primary determinant of this physiological feature.

Mechanical determinants of the energy cost of running at the half-marathon pace.

BACKGROUND: The aim of this study was to determine the influence of spring mass model characteristics (e.g. stiffness) and Achilles tendon properties in determining the energy cost of running in half marathon runners. METHODS: Achilles tendon characteristics (i.e. cross-sectional area -ATCSA- and resting length -ATL-) were measured on 32 males by means of an ultrasound apparatus the day before a half marathon race. After these measurements the energy cost of running (C) was determined while the subjects run on a treadmill at the speed (vT) they were expected to maintain during the race (vR); the vertical (kvert) and leg (kleg) stiffness were calculated based on kinematic data. RESULTS: No differences were observed between vT and vR. Higher values of vT were associated with larger values of kleg and kvert. The faster runners (with larger vT) were the ones with the lower C (r=-0.43, P<0.05) and the larger ATCSA (r=0.46, P<0.01). No relationship was found between C and ATCSA but C was lower in runners with longer ATL (r=-0.52, P<0.001). Finally, no relationship was found between kleg or kvert and C, but runners with larger kvert were also those with the larger ATCSA (r=0.45, P<0.01). CONCLUSIONS: These findings underline the correlation between spring-mass model parameters and Achilles tendon characteristics in half-marathon runners; they further show how these parameters influence the half marathon pace and the energy cost of running at this pace.

Effects of Different Training Intensity Distribution in Recreational Runners.

Purpose: To compare the impact of two different training intensity distributions in terms of conditional and performance parameters and spent time to training in recreational athletes. Methods: Two different training intensity distribution model were performed for 8 weeks by 38 recreational runners. Runners recruited were randomly assigned to 2 different training models based on HR intensity detected with maximal test. The percentage distribution splitted in zone 1, 2, and 3 were by 77/3/20 and 40/50/10 in polarized endurance training group (PET) and focused endurance training (FOC) group, respectively. Programs were balanced for total training impulse (TRIMP). To evaluate effects of training, before and after treatment were performed a maximal exercise test to determine Maximal Oxygen Uptake (V'O2max), Ventilatory Threshold (VT), respiratory-compensation point (RCT) Running Economy (RE), and 2 Km performance. To investigate the effects of training on muscular performance were performed one repetition maximum (1 RM), squat jump (SJ), and counter movement jump (CMJ). Results: Both groups significantly improved their velocity at V'O2max (3.2 and 4.0%), at VT (4.0 and 3.2%), RCT (5.7 and 3.4%), the average velocity in 2 Km performance (3.5 and 3.0%) and RE (-5.3 and -8.7%) for PET and FOC, respectively for each variable. No differences were found between the groups on any parameter investigated except about the total training time (PET = 29.9 ± 3.1 h and FOC = 24.8 ± 2.0 h). Conclusion: Focused Endurance Training obtains similar improvements than Polarized Endurance Training saving 17% of training time in recreational runners.

Neuromuscular Fatigue Does Not Impair the Rate of Force Development in Ballistic Contractions of Submaximal Amplitudes.

The effect of muscle fatigue on rate of force development (RFD) is usually assessed during tasks that require participants to reach as quickly as possible maximal or near-maximal force. However, endurance sports require athletes to quickly produce force of submaximal, rather than maximal, amplitudes. Thus, this study investigated the effect of muscle fatigue induced by long-distance running on the capacity to quickly produce submaximal levels of force. Twenty-one male amateur runners were evaluated before and shortly after a half-marathon race. Knee extensors force was recorded under maximal voluntary and electrically evoked contractions. Moreover, a series of ballistic contractions at different submaximal amplitudes (from 20 to 100% of maximal voluntary force) was obtained, by asking the participants to reach submaximal forces as fast as possible. The RFD was calculated for each contraction. After the race, maximal voluntary activation, resting doublet twitch, maximal force, and RFD during maximal contraction decreased (-12, -12, -21, and -19%, respectively, all P-values < 0.0001). Nevertheless, the RFD values measured during ballistic contractions up to 60% of maximal force were unaffected (all P-values > 0.4). Long-distance running impaired the capacity to quickly produce force in ballistic contractions of maximal, but not of submaximal, amplitudes. Overall, these findings suggest that central and peripheral fatigue do not affect the quickness to which muscle contracts across a wide range of submaximal forces. This is a relevant finding for running and other daily life activities that rely on the production of rapid submaximal contractions rather than maximal force levels.

Women show similar central and peripheral fatigue to men after half-marathon.

Women are known to be less fatigable than men in single-joint exercises, but fatigue induced by running has not been well understood. Here we investigated sex differences in central and peripheral fatigue and in rate of force development (RFD) in the knee extensors after a half-marathon run. Ten male and eight female amateur runners (aged 25-50 years) were evaluated before and immediately after a half-marathon race. Knee extensors forces were obtained under voluntary and electrically evoked isometric contractions. Maximal voluntary isometric contraction (MVC) force and peak RFD were recorded. Electrically doublet stimuli were delivered during the MVC and at rest to calculate the level of voluntary activation and the resting doublet twitch. After the race, decreases in MVC force (males: -11%, effect size [ES] 0.52; females: -11% ES 0.33), voluntary activation (males: -6%, ES 0.87; females: -4%, ES 0.72), and resting doublet twitch (males: -6%, ES 0.34; females: -8%, ES 0.30) were found to be similar between males and females. The decrease in peak RFD was found to be similar between males and females (males: -14%, ES 0.43; females: -15%, ES 0.14). Half-marathon run induced both central and peripheral fatigue, without any difference between men and women. The maximal and explosive strength loss was found similar between sexes. Together, these findings do not support the need of sex-specific training interventions to increase the tolerance to neuromuscular fatigue in half-marathoners.

Sympatho-adrenergic activation by endurance exercise: Effect on metanephrines spillover and its role in predicting athlete's performance.

BACKGROUND: The sympatho-adrenergic activation during exercise is implicated in many cardiovascular respiratory and metabolic adaptations which have been thought to partially explain the different levels of performance observed between trained and untrained subjects. To date, no evidence exists about the association between competition performance and markers of "acute stress response". We designed this study to investigate; (i) the acute sympatho-adrenergic activation during endurance exercise in recreational runners by measuring plasma levels of free metanephrine (MN) and normethanephrine (NMN) before and after a half-marathon run; (ii) the association between the metanephrines levels and the running time. METHODS: 26 amateur runners (15 males, 11 females) aged 30 to 63 years were enrolled. The quantification of MN and NMN was performed by LC-MS/MS. Anthropometric ergonomic and routine laboratory data were recorded. Statistical analyses included paired T-test, univariate and multivariate regressions. RESULTS: The post-run values of MN and NMN displayed a nearly 3.5 and 7 fold increase respectively compared to the baseline values (p < 0.0001 for both). NMN pre-run values and pre/post run delta values showed a significant direct and inverse association (p = 0.021 and p = 0.033, respectively) with running performance. No correlations were found for MN values. CONCLUSION: NMN is a reliable marker of sympatho-adrenergic activation by exercise and can predict endurance performance in the individual athlete. Adaptation phenomenon occurring not only in the adrenal medulla might represent the biological mechanism underlying this association. Further studies on sympatho-adrenergic activation, competition performance and training status should contemplate the measurement of these metabolites instead of their unstable precursors.

Fatigue-induced dissociation between rate of force development and maximal force across repeated rapid contractions.

We examined whether the presence of fatigue induced by prolonged running influenced the time courses of force generating capacities throughout a series of intermittent rapid contractions. Thirteen male amateur runners performed a set of 15 intermittent isometric rapid contractions of the knee extensor muscles, (3s/5s on/off) the day before (PRE) and immediately after (POST) a half marathon. The maximal voluntary contraction force, rate of force development (RFDpeak), and their ratio (relative RFDpeak) were calculated. At POST, considering the first (out of 15) repetition, the maximal force and RFDpeak decreased (p<0.0001) at the same extent (by 22±6% and 24±22%, respectively), resulting in unchanged relative RFDpeak (p=0.6). Conversely, the decline of RFDpeak throughout the repetitions was more pronounced at POST (p=0.02), thus the decline of relative RFDpeak was more pronounced (p=0.007) at POST (-25±13%) than at PRE (-3±13%). The main finding of this study was that the fatigue induced by a half-marathon caused a more pronounced impairment of rapid compared to maximal force in the subsequent intermittent protocol. Thus, the fatigue-induced impairment in rapid muscle contractions may have a greater effect on repeated, rather than on single, attempts of maximal force production.

Influence of ABO blood group on sports performance.

BACKGROUND: Despite being a recessive trait, the O blood group is the most frequent worldwide among the ABO blood types. Since running performance has been recognized as a major driver of evolutionary advantage in humans, we planned a study to investigate whether the ABO blood group may have an influence on endurance running performance in middle-aged recreational athletes. METHODS: The study population consisted of 52 recreational, middle-aged, Caucasian athletes (mean age: 49±13 years, body mass index, 23.4±2.3 kg/m2), regularly engaged in endurance activity. The athletes participated to a scientific event called "Run for Science" (R4S), entailing the completion of a 21.1 km (half-marathon) run under competing conditions. The ABO blood type status of the participants was provided by the local Service of Transfusion Medicine. RESULTS: In univariate analysis, running performance was significantly associated with age and weekly training, but not with body mass index. In multiple linear regression analysis, age and weekly training remained significantly associated with running performance. The ABO blood group status was also found to be independently associated with running time, with O blood type athletes performing better than those with non-O blood groups. Overall, age, weekly training and O blood group type explained 62.2% of the total variance of running performance (age, 41.6%; training regimen, 10.5%; ABO blood group, 10.1%). CONCLUSIONS: The results of our study show that recreational athletes with O blood group have better endurance performance compared to those with non-O blood group types. This finding may provide additional support to the putative evolutionary advantages of carrying the O blood group.

Middle-distance running acutely influences the concentration and composition of serum bile acids: Potential implications for cancer risk?

BACKGROUND: This study was aimed to investigate the acute effect of medium-distance running on bile acids concentration and composition, in order to verify whether the positive impact of physical exercise on cancer risk may also be mediated by variation of bile acids concentration and composition in serum. METHODS: The concentration and composition of serum bile acids was analyzed in 30 middle-aged and healthy recreational athletes with a reference liquid chromatography-mass spectrometry technique, immediately before and shortly after the end of the running trial. The concentration of bile acids after the run was adjusted for plasma volume change. RESULTS: All athletes successfully completed the trial. After correction of values for the individual plasma volume change calculated after the run, the serum concentration of total bile acids was found to be significantly reduced by approximately 46%. A statistically significant decrease was observed for cholic, deoxycholic, chenodeoxycholic, ursodeoxycholic, glycoursodeoxycholic and hyodeoxycholic acids, whereas the concentration of the remaining compounds remained unvaried after the run. A considerable variation of bile acids profile was also observed. No significant association was found between running performance and variation of bile acids concentrations. CONCLUSION: These results show that middle distance running acutely decreases the concentration of total bile acids in serum, especially that of the more mutagenic and carcinogenic compounds, so providing an intriguing support to the favorable effects of physical exercise for lowering the risk of many gastrointestinal cancers.

Decrease of muscle fiber conduction velocity correlates with strength loss after an endurance run.

Monitoring surface electromyographic (EMG) signals can provide useful insights for characterizing muscle fatigue, which is defined as an exercise-induced strength loss. This experiment investigated the muscle fiber conduction velocity (CV) changes induced by an endurance run. The day before and immediately after a half-marathon run (21.097 km) 11 amateur runners performed maximum voluntary contractions (MVCs) of knee extensor muscles. During the MVC, multichannel EMG was recorded from the vastus lateralis and EMG amplitude and CV were calculated. After the run, knee extensors showed a decreased strength (-13 ± 9%, p = 0.001) together with a reduction in EMG amplitude (-13 ± 10%, p = 0.003) and in CV (-6 ± 8%, p = 0.032). Knee extensor strength loss positively correlated with vastus lateralis CV differences (r = 0.76, p = 0.006). Thus, the exercises-induced muscle fatigue was associated not only with a decrease in EMG amplitude, but also with a reduction in CV. This finding suggests that muscle fibers with higher CV (i.e. those with greater fiber size) were the most impaired during strength production after an endurance run.

DNA injury is acutely enhanced in response to increasing bulks of aerobic physical exercise.

The aim of this study was to evaluate DNA damage in response to increasing bulks of aerobic physical exercise. Fifteen adult and trained athletes performed four sequential trials with increasing running distance (5-, 10-, 21- and 42-km) in different periods of the year. The γ-H2AX foci parameters were analyzed before and 3h after the end of each trial. The values of all γ-H2AX foci parameters were enhanced after the end of each trial, with values gradually increasing from the 5- to the 42-km trial. Interestingly, a minor increase of γ-H2AX foci was still evident after 5- to 10-km running, but a much higher increase occurred when the running distance exceeded 21km. The generation of DNA injury was then magnified by running up to 42-km. The increase of each γ-H2AX foci parameter was then found to be associated with both running distance and average intensity. In multivariate linear regression analysis, the running distance was significantly associated with average intensity and post-run variation in the percentage of cells with γ-H2AX foci. We can hence conclude that aerobic exercise may generate an acute DNA damage in trained athletes, which is highly dependent upon running distance and average intensity.