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Volume 7
Issue 10
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Sports, Volume 7, Issue 10 (October 2019) – 13 articles

Cover Story (view full-size image): The aim of this study was to investigate the effects of different combinations of concentric and eccentric resistance training programs on traditional and alternative hamstrings-to-quadriceps (H:Q) ratios. Our findings suggest eccentric exercise for quadriceps and hamstrings as the most beneficial training program for inducing increases in the traditional functional H:Q ratio. However, different resistance training strategies may be needed to also elicit increases in the alternative rate of torque development, muscle size, and muscle activation H:Q ratios for fully restoring muscle balance and reducing potential hamstrings and knee ligament injury risk. View this paper.
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16 pages, 2938 KiB  
Article
Post-Exercise Recovery Following 30-Day Supplementation of Trans-Resveratrol and Polyphenol-Enriched Extracts
by Edward Jo, Rachel Bartosh, Alexandra T. Auslander, Dean Directo, Adam Osmond and Michael WH Wong
Sports 2019, 7(10), 226; https://doi.org/10.3390/sports7100226 - 20 Oct 2019
Cited by 5 | Viewed by 4328
Abstract
Background: The purpose of this study was to investigate the effects of 30-day consumption of trans-resveratrol and polyphenol-enriched extracts on indices of exercise-induced muscle damage (EIMD) and performance following eccentric-loaded resistance exercise (ECRE). Methods: Following 30 days of resveratrol-polyphenol (RES) (n = [...] Read more.
Background: The purpose of this study was to investigate the effects of 30-day consumption of trans-resveratrol and polyphenol-enriched extracts on indices of exercise-induced muscle damage (EIMD) and performance following eccentric-loaded resistance exercise (ECRE). Methods: Following 30 days of resveratrol-polyphenol (RES) (n = 10) or placebo control (CTL) (n = 12) supplementation, subjects performed a bout of ECRE to induce EIMD. EIMD biomarkers, perceived soreness, pain threshold and tolerance, range of motion, and performance were measured before and 24 and 48 h after ECRE. Results: CTL subjects demonstrated increased soreness at 24 (p = 0.02) and 48 h (p = 0.03) post-ECRE, while RES subjects reported increased soreness at 24 h post-ECRE (p = 0.0003). CTL subjects exhibited decreased pain threshold in the vastus lateralis at 24 h post-ECRE (p = 0.03). CTL subjects also displayed decreased pain tolerance in the vastus intermedius at 24 h post-ECRE (p = 0.03) and the vastus lateralis at 24 (p = 0.003) and 48 h (p = 0.003). RES participants showed no change in pain threshold or tolerance from baseline. CTL subjects showed a decrease in mean (p = 0.04) and peak power (p = 0.04) at 24 h post-ECRE, while RES participants demonstrated no changes from baseline. No between-group differences were observed for the changes in serum creatine kinase. Serum C-reactive protein increased similarly in both groups at 24 h post-ECRE (p < 0.002), remaining elevated in CTL subjects while RES participants demonstrated a decline from 24 to 48 h (p = 0.04). Serum interleukin 6 increased at 24 h post-ECRE in both groups (p < 0.003) followed by a decrease from 24 to 48 h, returning to baseline levels only for RES subjects. Conclusion: Trans-resveratrol and polyphenol-enriched extract supplementation may support the attenuation of soreness and inflammation and improve performance recovery following ECRE without modulation of indirect biomarkers of EIMD. Full article
(This article belongs to the Special Issue Skeletal Muscle Metabolism in Exercise)
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<p>Schematic of the experimental timeline. ICF = informed consent form, EHHQ = Exercise Health History Questionnaire, DXA = dual-energy X-ray absorptiometry, 1RM = one-repetition maximum, ECRE = eccentric resistance exercise, EIMD = exercise-induced muscle damage.</p> Full article ">Figure 2
<p>Perceived muscle soreness at rest at baseline, 24- and 48-h post-ECRE. ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol. * Significant increase from baseline (<span class="html-italic">p</span> = 0.0003); ^ Significant increase from baseline (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 3
<p>Perceived muscle soreness under muscular tension at baseline, 24- and 48-h post- ECRE. ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol. * Significant increase from baseline (<span class="html-italic">p</span> &lt; 0.0005); ^ Significant increase from baseline (<span class="html-italic">p</span> = 0.01); # Significant increase than baseline (<span class="html-italic">p</span> = 0.007)</p> Full article ">Figure 4
<p>Change in lower-body flexibility at 24- and 48-h post-ECRE. ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol.</p> Full article ">Figure 5
<p>Mean power as a percentage of baseline at 24- and 48-h post-ECRE. MP = mean power, ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol. * Significant decrease from baseline (<span class="html-italic">p</span> = 0.04).</p> Full article ">Figure 6
<p>Peak power as a percentage of baseline at 24- and 48-h post-ECRE. PP = peak power, ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol. * Significant decrease from baseline (<span class="html-italic">p</span> = 0.04).</p> Full article ">Figure 7
<p>Serum creatine kinase (CK) at baseline and 24- and 48-h post-ECRE (left), and area under the curve (AUC) (right). ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol. * Significant increase from baseline (<span class="html-italic">p</span> &lt; 0.005); ^ Significant decrease from 24 h post-ECRE (<span class="html-italic">p</span> &lt; 0.007).</p> Full article ">Figure 8
<p>Serum C-reactive protein (CRP) at baseline and 24- and 48-h post-ECRE (left), and area under the curve (AUC) (right). ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol. * Significant increase from baseline (<span class="html-italic">p</span> &lt; 0.002); ^ Significant decrease from 24 h post-ECRE (<span class="html-italic">p</span> = 0.04).</p> Full article ">Figure 9
<p>Serum interleukin 6 (IL6) at baseline and 24- and 48-h post-ECRE (left), and area under the curve (AUC) (right). ECRE = eccentric resistance exercise, CTL = placebo, RES = resveratrol. * Significant increase from baseline (<span class="html-italic">p</span> &lt; 0.003); ^ Significant decrease from 24 h post-ECRE (<span class="html-italic">p</span> &lt; 0.0001).</p> Full article ">
10 pages, 824 KiB  
Article
Heart Rate Variability, Neuromuscular and Perceptual Recovery Following Resistance Training
by Andrew A. Flatt, Liam Globensky, Evan Bass, Brooke L. Sapp and Bryan L. Riemann
Sports 2019, 7(10), 225; https://doi.org/10.3390/sports7100225 - 18 Oct 2019
Cited by 16 | Viewed by 7187
Abstract
We quantified associations between changes in heart rate variability (HRV), neuromuscular and perceptual recovery following intense resistance training (RT). Adult males (n = 10) with >1 year RT experience performed six sets to failure with 90% of 10 repetition maximum in the [...] Read more.
We quantified associations between changes in heart rate variability (HRV), neuromuscular and perceptual recovery following intense resistance training (RT). Adult males (n = 10) with >1 year RT experience performed six sets to failure with 90% of 10 repetition maximum in the squat, bench press, and pull-down. Changes (∆) from pre- to immediately (IP), 24 and 48 h post-RT were calculated for neuromuscular performance markers (counter-movement jump peak power and mean concentric bench press and squat velocity with load corresponding to 1.0 m∙s−1) and perceived recovery and soreness scales. Post-waking natural logarithm of the root-mean square of successive differences (LnRMSSD) in supine and standing positions were recorded pre-RT (5 day baseline), IP and two mornings post-RT. All parameters worsened at IP (p < 0.05). LnRMSSD measures were not different from baseline by 24 h. Neuromuscular markers were not different from pre-RT by 48 h. Perceptual measures remained suppressed at 48 h. No significant associations among ∆ variables were observed (p = 0.052–0.978). These data show varying timeframes of recovery for HRV, neuromuscular and perceptual markers at the group and individual level. Thus, post-RT recovery testing should be specific and the status of one metric should not be used to infer that of another. Full article
(This article belongs to the Special Issue Monitoring Physiological Adaptation to Physical Training)
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<p>Individual time-course of recovery following resistance training (RT). BL = baseline; IP = 10 min post-RT. Light and dark gray shaded areas represent smallest worthwhile change thresholds (0.5 × intra-individual BL coefficient of variation) [<a href="#B30-sports-07-00225" class="html-bibr">30</a>] for supine and standing natural logarithm of the root mean square of successive differences (LnRMSSD), respectively.</p> Full article ">
10 pages, 1745 KiB  
Article
Muscle Activation in Traditional and Experimental Barbell Bench Press Exercise: A Potential New Tool for Fitness Maintenance
by Andrea Melani, Giuliana Gobbi, Daniela Galli, Cecilia Carubbi, Elena Masselli, Luca Maria Neri, Gaspare Giovinco, Antonio Cicchella, Laura Galuppo, Valentina Presta, Mauro Vaccarezza, Marco Vitale and Prisco Mirandola
Sports 2019, 7(10), 224; https://doi.org/10.3390/sports7100224 - 17 Oct 2019
Cited by 3 | Viewed by 15794
Abstract
Background: The bench press exercise (BP) is commonly practiced in both recreational and professional training. The weight is lowered from a position where the elbows are at a 90° angle at the start and <90° at the end of eccentric phase, and then [...] Read more.
Background: The bench press exercise (BP) is commonly practiced in both recreational and professional training. The weight is lowered from a position where the elbows are at a 90° angle at the start and <90° at the end of eccentric phase, and then returned to the elbows extended position. In order to focus the exercise more on the triceps brachii (TB) rather than the pectoralis major (PM), the inter-handle distance (IHD) is decreased diminishing the involvement of the PM in favor of the TB. Purpose: To improve performance of the exercise by reducing force dissociation and transmitting 100% of the external load to the muscle tissue we propose a prototype of the barbell with a bar on which two sleeves are capable of sliding. The dynamic modifications of the IHD keep the elbow flexion angle constant at 90°. Results: Analysis of the inter-handle distance (IHD) signals of the upper body muscles showed a marked increase in muscle activity using the experimental barbell for the PM (19.5%) and for the biceps brachii (173%). Conclusions: The experimental barbell increased the muscle activity typical of the bench press exercise, obtaining the same training induction with a lower load and consequently preventing articular stress. Full article
(This article belongs to the Special Issue Physiological Responses and Adaptations in Resistance Exercise)
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<p>Bench press dynamic. Schematic representation of angles formed by the elbows and barbells during the performance of a traditional bench press exercise. The angle of the line hand–elbow and the barbell is reported. When the barbell is positioned on its support the angle is 90° (panel <b>A</b>). The start and end position are shown in panels <b>B</b> and <b>C</b>, respectively.</p> Full article ">Figure 2
<p>Execution with the free-grip barbell. The grips are constantly aligned with the vertical to the elbow (90° angle), allowing both an overload optimization and a complete muscular excursion from maximum elongation (panel <b>1</b>) to maximum shortening (panel <b>3</b>), an intermediate position between the maximum elongation and the maximum shortening (panel <b>2</b>).</p> Full article ">Figure 3
<p>Schematic representation of the device. The handle (mobile grip) is tied to a cable (1<sup>st</sup> end, red line) that runs in the opposite direction through a pulley engaging (2<sup>nd</sup> end) the contralateral grip. A second cable (blue line) is engaged to the handles and run on the pulley at the opposite end of the barbell.</p> Full article ">Figure 4
<p>Electromyography <b>(</b>EMG) test performed both with the locked barbell (TB) (blue line), and the free grip-barbell (EB) (red line). Numeric EMG data was plotted on line-graphs by superimposing the two-to-two trials so that the test with the traditional barbell (blue line) and test with the experimental barbell (red line) would be on the same chart. A shift of the x axis data (time) was performed to synchronize the EMG peaks of the first test with the peaks of the second. An exemplificative result is reported.</p> Full article ">Figure 5
<p>EMG analysis of upper body muscles during bench press training. EMG test were performed both with the locked barbell (TB) and the free-grip barbell (EB). Electromyography of the pectoralis major (PM), anterior deltoid front bands (AD), triceps brachii (TB), and biceps brachii (BB) is shown. Mean values of EMG data and EMG normalized through the values of maximum voluntary reduction (MCV) are reported. For PM EMG the critical value of W is 0, for N = 8; <span class="html-italic">p</span> ≤ 0.01. For BB EMG the W-value is 1, for N = 9; <span class="html-italic">p</span> ≤ 0.01. For DA EMG the W-value is 11, for N = 7; <span class="html-italic">p</span> &gt; 0.05. For TB EGF the t-value is 0.643164; <span class="html-italic">p</span> &gt; 0.53.</p> Full article ">
12 pages, 1217 KiB  
Article
Effect of Thirst-Driven Fluid Intake on 1 H Cycling Time-Trial Performance in Trained Endurance Athletes
by Maxime Perreault-Briere, Jeff Beliveau, David Jeker, Thomas A. Deshayes, Ana Duran and Eric D. B. Goulet
Sports 2019, 7(10), 223; https://doi.org/10.3390/sports7100223 - 14 Oct 2019
Cited by 10 | Viewed by 3918
Abstract
A meta-analysis demonstrated that programmed fluid intake (PFI) aimed at fully replacing sweat losses during a 1 h high-intensity cycling exercise impairs performance compared with no fluid intake (NFI). It was reported that thirst-driven fluid intake (TDFI) may optimize cycling performance, compared with [...] Read more.
A meta-analysis demonstrated that programmed fluid intake (PFI) aimed at fully replacing sweat losses during a 1 h high-intensity cycling exercise impairs performance compared with no fluid intake (NFI). It was reported that thirst-driven fluid intake (TDFI) may optimize cycling performance, compared with when fluid is consumed more than thirst dictates. However, how TDFI, compared with PFI and NFI, impacts performance during a 1 h cycling time-trial performance remains unknown. The aim of this study was to compare the effect of NFI, TDFI and PFI on 1 h cycling time-trial performance. Using a randomized, crossover and counterbalanced protocol, 9 (7 males and 2 females) trained endurance athletes (30 ± 9 years; Peak V · O2∶ 59 ± 8 mL·kg−1·min−1) completed three 1 h cycling time-trials (30 °C, 50% RH) with either NFI, TDFI or PFI designed to maintain body mass (BM) at ~0.5% of pre-exercise BM. Body mass loss reached 2.9 ± 0.4, 2.2 ± 0.3 and 0.6 ± 0.2% with NFI, TDFI and PFI, respectively. Heart rate, rectal and mean skin temperatures and ratings of perceived exertion and of abdominal discomfort diverged marginally among trials. Mean distance completed (NFI: 35.6 ± 1.9 km; TDFI: 35.8 ± 2.0; PFI: 35.7 ± 2.0) and, hence, average power output maintained during the time-trials did not significantly differ among trials, and the impact of both PFI and TDFI vs. NFI was deemed trivial or unclear. These findings indicate that neither PFI nor TDFI are likely to offer any advantage over NFI during a 1 h cycling time-trial. Full article
(This article belongs to the Special Issue Hydration in Sport and Exercise)
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<p>Schematic of the research protocol.</p> Full article ">Figure 2
<p>Changes in heart rate (<b>A</b>), rectal temperature (<b>B</b>), and mean skin temperature (<b>C</b>) across time among conditions. Results are means ± SD. * <span class="html-italic">p</span> &lt; 0.05 between PFI and NFI, # <span class="html-italic">p</span> &lt; 0.05 between PFI and TDFI, ‡ significant time effect.</p> Full article ">Figure 3
<p>Changes in perceived exertion (<b>A</b>) and thirst (<b>B</b>) across time among conditions. Results are means ± SD. AU: arbitrary units. * <span class="html-italic">p</span> &lt; 0.05 between PFI and NFI, # <span class="html-italic">p</span> &lt; 0.05 between PFI and TDFI, † <span class="html-italic">p</span> &lt; 0.05 between TDFI and NFI, ‡ significant time effect.</p> Full article ">Figure 4
<p>Changes in power output across time among conditions. Results are means ± SD. ‡ significant time effect.</p> Full article ">
13 pages, 666 KiB  
Article
Development of Physical Fitness among the Top 10 Boys and Girls in Sport Schools: A 10-Year Cohort Analysis
by Andreas Roth, Steffen C. E. Schmidt, Sina Hartmann, Ilka Seidel, Swantje Scharenberg and Klaus Bös
Sports 2019, 7(10), 222; https://doi.org/10.3390/sports7100222 - 12 Oct 2019
Cited by 2 | Viewed by 2785
Abstract
In this study, we aimed to measure the development of physical fitness (PF) of 10 different cohorts in grade 4 and 8 different cohorts in grade 7 at 18 sport schools of North Rhine-Westphalia, Germany. A total of 11,451 subjects (3979 female, 7472 [...] Read more.
In this study, we aimed to measure the development of physical fitness (PF) of 10 different cohorts in grade 4 and 8 different cohorts in grade 7 at 18 sport schools of North Rhine-Westphalia, Germany. A total of 11,451 subjects (3979 female, 7472 male) aged 8–12 from the past 10 years were assessed using the German Motor Test (DMT) in grade 4. We tested 2614 subjects (1032 girls, 1582 boys) aged 11–15 from the past eight years using the DMT in grade 7. PF talents were defined as the top 10 boys and top 10 girls of each cohort. Linear regression was calculated to assess the development of PF. The PF of all subjects remained stable in grade 4 and declined in grade 7. The PF of the top 10 boys and top 10 girls increased in both grades. The improvements were stronger in grade 7 (female: rates of change (β) = 0.80; male: β = 0.76) than in grade 4 (female: β = 0.36; male: β = 0.32). Sit-ups and push-ups showed the highest change rates. The increase in PF of the top 10 boys and girls can be interpreted as a success for sport schools. Due to the increasing number of test participants, the likelihood of finding top talent increased. However, the increase in PF in the top talents was only partly explained by an increase in the number of tested individuals. Full article
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<p>Means and 95% confidence of PF for different cohorts of boys and girls from grades 4 and 7.</p> Full article ">
14 pages, 1073 KiB  
Article
Effects of Different Combinations of Concentric and Eccentric Resistance Training Programs on Traditional and Alternative Hamstrings-to-Quadriceps Ratios
by Cassio V. Ruas, Ronei S. Pinto, Guy G. Haff, Camila D. Lima and Lee E. Brown
Sports 2019, 7(10), 221; https://doi.org/10.3390/sports7100221 - 12 Oct 2019
Cited by 12 | Viewed by 4922
Abstract
Resistance training is often recommended for combined increases in traditional and alternative hamstrings-to-quadriceps (H:Q) ratios in order to reduce knee strength imbalance and associated hamstrings and knee ligament injury risk. The aim of this study was to investigate the effect of different concentric [...] Read more.
Resistance training is often recommended for combined increases in traditional and alternative hamstrings-to-quadriceps (H:Q) ratios in order to reduce knee strength imbalance and associated hamstrings and knee ligament injury risk. The aim of this study was to investigate the effect of different concentric and eccentric resistance training programs on traditional and alternative H:Q ratios. Forty male volunteers were assigned to one of 4 groups: concentric quadriceps and concentric hamstrings (CON/CON, n = 10), eccentric quadriceps and eccentric hamstrings (ECC/ECC, n = 10), concentric quadriceps and eccentric hamstrings (CON/ECC, n = 10), or no training (control (CNTRL), n = 10). Traditional conventional (CR) and functional (FR), alternative rate of torque development (RTD), muscle size (MS), and muscle activation (MA) H:Q ratios were measured before and after six weeks of unilateral nondominant knee extension–flexion resistance training performed on an isokinetic dynamometer. The ECC/ECC training significantly increased FR (pre = 0.75 ± 0.11; post = 0.85 ± 0.15), whereas the lack of training (CNTRL) decreased the RTD H:Q ratio (pre = 1.10 ± 0.67; post = 0.73 ± 0.33). There were no differences between groups for the other traditional and alternative ratios following resistance training protocols. These findings suggest eccentric exercise for quadriceps and hamstrings as the most beneficial training program for inducing increases in the traditional FR. However, different resistance training strategies may be needed to also elicit increases in the alternative RTD, MS, and MA H:Q ratios for fully restoring muscle balance and reducing potential hamstrings and knee ligament injury risk. Full article
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<p>Study design and training programs for each group, including training sets, repetitions, and velocity per week for concentric (CON) and eccentric (ECC) muscle actions, and time intervals between pre- and post-testing and training sessions.</p> Full article ">Figure 2
<p>Means and SDs of hamstrings-to-quadriceps (H:Q) conventional (CR), functional (FR), rate of torque development (RTD), muscle size (MS), and muscle activation (MA) ratios between pre- and post-tests for concentric/concentric (CON/CON), eccentric/eccentric (ECC/ECC), concentric/eccentric (CON/ECC), and control (CNTRL) groups. The open circles demonstrate individual pre- to post-testing data.* Significantly greater than pre-test. # Significantly greater than post-test.</p> Full article ">
12 pages, 9770 KiB  
Article
Acute Metabolic Changes with Lower Leg-Positioned Wearable Resistances during Submaximal Running in Endurance-Trained Runners
by Allister P. Field, Nicholas Gill, Aaron M. Uthoff and Dan Plews
Sports 2019, 7(10), 220; https://doi.org/10.3390/sports7100220 - 11 Oct 2019
Cited by 4 | Viewed by 2711
Abstract
The aim of this study was to determine the acute metabolic effects of different magnitudes of wearable resistance (WR) attached to the lower leg during submaximal running. Fifteen endurance-trained runners (37.8 ± 6.4 years; 1.77 ± 0.7 m; 72.5 ± 9.8 kg; 58.9 [...] Read more.
The aim of this study was to determine the acute metabolic effects of different magnitudes of wearable resistance (WR) attached to the lower leg during submaximal running. Fifteen endurance-trained runners (37.8 ± 6.4 years; 1.77 ± 0.7 m; 72.5 ± 9.8 kg; 58.9 ± 7.4 L/min VO2max; 45.7 ± 5.8 min 10 K run time) completed seven submaximal running trials with WR loads of 0, 0.5, 1, 1.5, 2, 2.5 and 3% body mass (BM). Based on regression data, for every 1% BM increase of additional load, oxygen consumption (VO2) increased by 2.56% and heart rate increased by 1.16%. Inferential based analysis identified that ≤1% BM were enough to elicit responses in VO2, with a possible small increase (effect size (ES), 90% confidence interval (CI): 0.22, 0.17 to 0.39), while 3% BM loads produced a most likely very large increase (ES, 90% CI: 0.51, 0.42 to 0.60). A training load score was extrapolated using heart rate data to determine the amount of internal stress. An additional 1% BM resulted in an extra 0.39 (0.29 to 0.47) increase in internal stress over five minutes. Lower leg WR elicited substantial increases in lactate production from the lightest loading (0.5% BM), with a likely moderate increase (ES, 90% CI: 0.49, 0.30 to 0.95). Lower-leg positioned WR provides a running-specific overload with loads ≥ 1% BM resulting in substantial changes in metabolic responses. Full article
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<p>Example of lower-leg wearable resistance loading pattern (0.5% BM) for a 70 kg runner.</p> Full article ">Figure 2
<p>Example of lower-leg wearable resistance loading pattern (1.5% BM) for a 70 kg runner.</p> Full article ">Figure 3
<p>Example of lower-leg wearable resistance loading pattern (2.5% BM) for a 70 kg runner.</p> Full article ">Figure 4
<p>Structure of testing sessions.</p> Full article ">Figure 5
<p>Mean percent increase in acute oxygen consumption to lower-leg WR for 5-min submaximal running trials compared to unloaded (90%CI).</p> Full article ">Figure 6
<p>Percent increase in acute heart rate response to lower-leg loaded WR for 5-min submaximal running trials compared to unloaded (± 90% CI).</p> Full article ">Figure 7
<p>Extrapolated Training Load Score (TSS) for lower-leg loaded WR for the equivalent of 10-min of running (± 90% CI).</p> Full article ">
11 pages, 220 KiB  
Article
Effects of Plyometric Training on Sprint Running Performance in Boys Aged 9–12 Years
by Nobuaki Tottori and Satoshi Fujita
Sports 2019, 7(10), 219; https://doi.org/10.3390/sports7100219 - 10 Oct 2019
Cited by 8 | Viewed by 5580
Abstract
Skilled sprinting is fundamental in many sports, especially to improve athletic performance in youth. This study therefore aimed to investigate the effect of plyometric training on sprint performance in boys aged 9–12 years. Twenty boys were divided into a plyometric training group ( [...] Read more.
Skilled sprinting is fundamental in many sports, especially to improve athletic performance in youth. This study therefore aimed to investigate the effect of plyometric training on sprint performance in boys aged 9–12 years. Twenty boys were divided into a plyometric training group (n = 9) and a control training group (n = 11). In both groups, participants performed respective training programs once per week for 8 weeks with measurements at baseline and post-intervention. Sprint performance was assessed by 50-m sprint time, sprint velocity, step frequency and step length at 10-m intervals. Jumping performance was assessed using horizontal, vertical and rebound jumps. The plyometric training group showed an improved sprint velocity at 20–30 m, 30–40 m and 40–50 m, and step length at 0–10 m, 20–30 m and 30–40 m (p < 0.05). Furthermore, only the plyometric group showed an increased standing long jump distance and rebound jump performance (p < 0.05). The control group did not show any significant changes in any variable. Our findings suggest that plyometric training in pre-adolescent boys improves sprint velocity and step length at the maximum velocity phase concomitant with increased horizontal and rebound jump performance. Full article
12 pages, 1596 KiB  
Article
Isometric Posterior Chain Peak Force Recovery Response Following Match-Play in Elite Youth Soccer Players: Associations with Relative Posterior Chain Strength
by Emma Constantine, Matt Taberner, Chris Richter, Matthew Willett and Daniel D. Cohen
Sports 2019, 7(10), 218; https://doi.org/10.3390/sports7100218 - 1 Oct 2019
Cited by 17 | Viewed by 5248
Abstract
The purpose of this study was to determine changes in two tests of lower limb isometric posterior chain force (IPC-F) following 90 min of match-play in elite youth soccer players and the interaction between relative strength and recovery profile. 14 players (age: 16 [...] Read more.
The purpose of this study was to determine changes in two tests of lower limb isometric posterior chain force (IPC-F) following 90 min of match-play in elite youth soccer players and the interaction between relative strength and recovery profile. 14 players (age: 16 ± 2 years) performed 3 × 3 second IPC-F tests unilaterally at 30° and 90° of knee and hip flexion pre- and post-match, +24 h, +48 h, and +72 h post-match. Peak force was recorded for both limbs, combined and expressed relative to bodyweight (N/kg). A two-way repeated measures analysis of variance was performed to determine differences in force output between joint angles, time intervals and subjects. As there was no interaction between angle and time (p = 0.260), we report the change between timepoints as mean ∆ in 90° + 30° IPC-F. Relative to pre-match IPC-F, there were significant decreases post (∆ = −18%; p > 0.001) and at +24 h (∆ = −8%; p = 0.040), no significant difference at +48 h (∆ = 0%; p = 0.992) and a significant increase at +72 h (∆ = +12%; p = 0.005). There was a large inter-individual variability in recovery profile at both angles and substantial differences between post-match deficits at 90° (−10.8%) compared to 30° (−20.7%). Higher pre-match IPC-F was correlated with the magnitude of IPC-F deficits at both angles and all time points (r = 0.56 to 0.70, p = < 0.01) except for post-match 90°. Regular IPC-F monitoring to determine the magnitude of match-induced fatigue and track recovery may help inform decision-making regarding modifications to individual players training load, particularly as there is a large inter-individual variability in response to competition. Further research is warranted to better understand and address the finding that stronger players showed larger force deficits and slower recovery following match-play. Full article
(This article belongs to the Special Issue Training, Screening and Monitoring in Soccer)
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<p>Isometric Posterior Chain Force (IPC-F) tests at 30° (<b>A</b>) and 90° (<b>B</b>).</p> Full article ">Figure 2
<p>Mean change in relative IPC-F (N/kg) between each time point tested (Pre-match, Post-match, +24 h, +48 h and +72 h). Violin and box plot represent variation across the data sets for each player in relation to mean and median values. ** indicates significant difference: Pre to Post, Post to +72 h, +24 h to +72 h; <span class="html-italic">p =</span> 0.000, Pre to +72 h and post to +48 h; <span class="html-italic">p =</span> 0.004, +48 h to +72 h; <span class="html-italic">p =</span> 0.005.</p> Full article ">Figure 3
<p>Correlation between pre-match IPC-F (N/kg) at 30° and 90° and Δ IPC-F post-match. CB = centre-back, CF = centre-forward, CM = centre-midfielder, FB = full-back, WIN = winger.</p> Full article ">Figure 4
<p>Correlation between pre-match IPC-F (N/kg) at 30° and 90° and Δ IPC-F at 48 h. CB = centre-back, CF = centre-forward, CM = centre-midfielder, FB = full-back, WIN = winger.</p> Full article ">Figure 5
<p>Correlation between pre-match IPC-F (N/kg) at 30° and 90° and Δ IPC-F at 72 h. CB = centre-back, CF = centre-forward, CM = centre-midfielder, FB = full-back, WIN = winger.</p> Full article ">
8 pages, 723 KiB  
Article
The Validity of Functional Threshold Power and Maximal Oxygen Uptake for Cycling Performance in Moderately Trained Cyclists
by Arne Sørensen, Tore Kristian Aune, Vegar Rangul and Terje Dalen
Sports 2019, 7(10), 217; https://doi.org/10.3390/sports7100217 - 1 Oct 2019
Cited by 21 | Viewed by 6964
Abstract
Cycling is a popular sport, and evaluation of the validity of tests to predict performance in competitions is important for athletes and coaches. Similarity between performance in sprints in mass-start bike races and in the laboratory is found, but, to our knowledge, no [...] Read more.
Cycling is a popular sport, and evaluation of the validity of tests to predict performance in competitions is important for athletes and coaches. Similarity between performance in sprints in mass-start bike races and in the laboratory is found, but, to our knowledge, no studies have investigated the relationship between laboratory measurements of maximal oxygen uptake (VO2max) and functional threshold power (FTP) with performance in official mass-start competitions. The purpose of this study was to evaluate the validity of a 20 min FTP test and VO2max as predictors for performance in an official mountain bike competition. Eleven moderately trained male cyclists at a local level participated in this study (age: 43 ± 5.1 years; height: 183.4 ± 5.4 m; weight: 84.4 ± 8.7 kg; body mass index: 25.1 ± 2.1). All subjects performed a 20 min FTP test in the laboratory to measure the mean power. In addition, the subjects completed an incremental test to exhaustion to determine VO2max. These two laboratory tests were analyzed together with the results from a 47 km mass-start mountain bike race, with a total elevation of 851 m. A significant relationship was found between the mean relative power (W/kg) for the 20 min FTP test and performance time in the race (r = −0.74, P < 0.01). No significant correlation was found between VO2max and cycling performance for these subjects (r = −0.37). These findings indicate that a 20 min FTP test is a more valid test for prediction of performance in mass-start bike races than a VO2max test for moderately trained cyclists. Full article
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<p>Race profile for the mass-start mountain bike race. Total distance: 47 km. Total elevation: 851 m. Altitude: 3–338 meters above mean sea level (MAMSL).</p> Full article ">Figure 2
<p>Plots of single sets of XY pairs for (<b>A</b>) relative FTP and race time; (<b>B</b>) FTP and race time; (<b>C</b>) VO<sub>2max</sub> and race time; and (<b>D</b>) weight and race time, respectively. Each circle indicates one participant.</p> Full article ">
9 pages, 2111 KiB  
Article
Is Physical Performance a Differentiating Element between More or Less Successful Football Teams?
by Jose Antonio Asian Clemente, Bernardo Requena, Igor Jukic, Jack Nayler, Alfredo Santalla Hernández and Christopher Carling
Sports 2019, 7(10), 216; https://doi.org/10.3390/sports7100216 - 30 Sep 2019
Cited by 26 | Viewed by 5531
Abstract
This study investigated the time-motion characteristics of football teams in the Spanish first division, in relation to their final competitive level as defined by league position (Champions League, Europa League, Upper mid-table, lower mid-table and relegation). Match observations (n = 9641) were [...] Read more.
This study investigated the time-motion characteristics of football teams in the Spanish first division, in relation to their final competitive level as defined by league position (Champions League, Europa League, Upper mid-table, lower mid-table and relegation). Match observations (n = 9641) were collected using a multiple-camera computerized tracking system during the 2013–2014 competitive season. The following match parameters were analyzed: total distance, relative distance (m·min−1), distance < 14 km·h−1, >14 km·h−1, between 14–21 km·h−1, >21 km·h−1, and >24 km·h−1. Total distance and distance at different velocities (>14, 21, and 24 km·h−1) in and out of ball possession were also analyzed. A repeated analysis of variance and a comparison of effect sizes were carried out to compare the performance of the teams. The analysis of the data showed differences in physical performance characteristics between competitive levels. The volume of distance covered in the variables analyzed did not relate to success in soccer. Both successful and unsuccessful teams presented the same running requirements at higher velocities. These findings provide valuable information about the physical demands of the running requirements according to their final position in the league table. Full article
(This article belongs to the Special Issue Applied Sport Science for Elite Athletes)
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<p>Organization of team groups according to the final classification in the season 2013–2014. P = position; Pl = played matches; W = matches won; D = matches Drawn; L = matches lost; Pt = points. Underlined letters represent the letters used to create the abbreviations of each group.</p> Full article ">Figure 2
<p>Variables analyzed to assess the locomotors demands of the matches.</p> Full article ">Figure 3
<p>Comparison of the physical demands between groups. UEFA Champions League (CL), UEFA Europa League (EL), Upper Middle Table (UMT), Lower Middle Table (LMT) and Relegation (R). Bars indicate uncertainty in the true mean changes with 90% confidence intervals. The trivial area was calculated from the smallest worthwhile change (SWC).</p> Full article ">
9 pages, 221 KiB  
Article
A Comparison of Machine versus Free-Weight Squats for the Enhancement of Lower-Body Power, Speed, and Change-of-Direction Ability during an Initial Training Phase of Recreationally-Active Women
by Neil A. Schwarz, Sean P. Harper, Andy Waldhelm, Sarah K. McKinley-Barnard, Shelley L. Holden and John E. Kovaleski
Sports 2019, 7(10), 215; https://doi.org/10.3390/sports7100215 - 30 Sep 2019
Cited by 8 | Viewed by 10651
Abstract
The purpose of this study was to examine differences between a free-weight squat (FWS) and machine squat (MS) during an initial resistance training phase for augmentation of performance tests in recreationally active women. Twenty-seven women (22.7 ± 3.5 years) were block-randomized to three [...] Read more.
The purpose of this study was to examine differences between a free-weight squat (FWS) and machine squat (MS) during an initial resistance training phase for augmentation of performance tests in recreationally active women. Twenty-seven women (22.7 ± 3.5 years) were block-randomized to three groups: FWS, MS, or control (CON) and completed pre- and post-testing sessions consisting of the squat one-repetition maximum (1-RM), vertical jump, pro-agility test, zig-zag change-of-direction (COD) test, and 30-meter sprint. Participants trained two sessions per week for six weeks by performing jumping, sprinting, and COD drills followed by FWS, MS, or no squats (CON). Peak jump power increased for CON (p = 0.03) and MS (p < 0.01) groups. Change in peak jump power was greater for the MS group compared with the FWS group (p = 0.05). Average jump power increased for the MS group (p < 0.01). Change in average jump power was greater for the MS group compared with the CON group (p = 0.04). Vertical jump height, pro-agility, 30-meter sprint, and zig-zag COD tests improved over time (p < 0.01), with no difference between groups (p > 0.05). Machine squat training maximized jumping power compared with FWS training and CON. Both resistance training groups and the CON group improved equally in the pro-agility, 30-meter sprint, and zig-zag COD tests. Machine squat training may provide performance-enhancing benefits of equal or superior value to those obtained with free-weight squat training in recreationally active women during an initial training mesocycle. These findings also stress the importance of task-specific training in this population of untrained women, as the control group improved in terms of performance to the same degree as both resistance training groups. Full article
(This article belongs to the Special Issue Physiological Responses and Adaptations in Resistance Exercise)
10 pages, 869 KiB  
Article
Hamstring-to-Quadriceps Ratio in Female Athletes with a Previous Hamstring Injury, Anterior Cruciate Ligament Reconstruction, and Controls
by Eleftherios Kellis, Nikiforos Galanis and Nikolaos Kofotolis
Sports 2019, 7(10), 214; https://doi.org/10.3390/sports7100214 - 28 Sep 2019
Cited by 14 | Viewed by 6839
Abstract
Muscle strength imbalances around the knee are often observed in athletes after anterior cruciate ligament (ACL) surgery and hamstring muscle injury. This study examined three hamstrings-to-quadriceps (H:Q) strength ratio types (conventional, functional, and mixed) in thirteen female athletes with a history of hamstring [...] Read more.
Muscle strength imbalances around the knee are often observed in athletes after anterior cruciate ligament (ACL) surgery and hamstring muscle injury. This study examined three hamstrings-to-quadriceps (H:Q) strength ratio types (conventional, functional, and mixed) in thirteen female athletes with a history of hamstring injury, fourteen basketball players following ACL reconstruction and 34 controls. The conventional (concentric H:Q) peak torque ratio was evaluated at 120°·s−1 and 240°·s−1. The functional (eccentric hamstring to concentric quadriceps) torque ratio was evaluated at 120°·s−1. Finally, the mixed (eccentric hamstrings at 30°·s−1 to concentric quadriceps at 240°·s−1) torque ratio was calculated. Both ACL and the hamstring-injured groups showed a lower quadriceps and hamstrings strength compared with controls (p < 0.05). However, non-significant group differences in the H:Q ratio were found (p > 0.05). Isokinetic assessment of muscle strength may be useful for setting appropriate targets of training programs for athletes with a history of ACL surgery or hamstring strain. However, isokinetic evaluation of the H:Q ratio is not injury—specific and it does not vary between different methods of calculating the H:Q ratio. Full article
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<p>Mean group values of concentric (H<sub>CON120</sub>) and eccentric (H<sub>ECC120</sub>) hamstrings and concentric (Q<sub>CON120</sub>) and eccentric (Q<sub>ECC120</sub>) quadriceps peak torque at an angular velocity of 120°·s<sup>−1</sup> for the control group (CG), the ACL reconstruction group (ACL), and the hamstring injured group (HIG) (error bars indicate standard deviation, * significant different compared with the GG, <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 2
<p>Mean group values of eccentric quadriceps (Q<sub>ECC30</sub>) and hamstrings (H<sub>ECC30</sub>) peak torque at 30°·s<sup>−1</sup> and concentric quadriceps (Q<sub>CON240</sub>) and hamstrings (H<sub>CON240</sub>) peak torque at 240°·s<sup>−1</sup> for the control group (CG), the ACL reconstruction group (ACL), and the hamstring injured group (HIG) (error bars indicate standard deviation, * significant different compared with the GG, <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">
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