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1.
Plant Dis ; 2024 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-38557242

RESUMO

Phoenix dactylifera L. is an economically and aesthetically important tree in the southwestern US. Approximately 4900 ha of dates are commercially grown for its edible fruit in the US, including about 1600 ha in the Yuma area and the Hyder Valley of Arizona (USDA, 2023). In October 2022, a severe rot was observed on three date palms in the Phoenix Metropolitan area. Early symptoms were brown spots that turned to a black scorch appearance extending along the leaf base and rachis, leading to the lower fronds' wilting, drying, and folding. As the disease progressed upwards, the terminal bud became necrotic and eventually collapsed. Isolation from the necrotic leaf lesions on a potato dextrose agar (PDA) consistently yielded a fast-growing fungus that was initially white with abundant fluffy aerial mycelium, which gradually turned dark olivaceous after growing at 22-25oC under 12 h light for a week. Pycnidial conidiomata formed on pine needles in a water agar were black and globose. Conidiogenous cells were hyaline and cylindrical. The conidia exhibited a thick-walled, ovoid to ellipsoid morphology, initially appearing hyaline and aseptate and transitioned to 1-septate with a dark brown, striated appearance, measuring 19.6 to 23.0 µm x 10.3 to 12.2 µm (n = 20). For molecular identification, genomic DNA was extracted from the mycelia of two isolates. Partial DNA sequences of the internal transcribed spacer (ITS) region of rDNA and ß-tubulin (TUB) gene were amplified and sequenced using primers ITS5/ITS4 (White et al. 1990) and Bt2a/Bt2b (Glass and Donaldson 1995). The resulting sequences of ITS (PP346666) and TUB (PP372690) were deposited in the GenBank. A BLASTn search of ITS and TUB sequences revealed a 99 to 100% similarity with the sequences (JX456475, KF766198, and OK338070) of Neodeightonia phoenicum strains causing palm rot in Greece (Ligoxigakis et al. 2013), leaf spot on pygmy date palm in China (Zhang and Song 2022), and an ex-type CBS 122528 culture. Based on these morphological and molecular data, the fungus was identified as N. phoenicum. A pathogenicity test was conducted twice in a greenhouse (daily temperatures:18 ~ 30 oC, relative humidity: 45% ~ 95%) on 4 healthy 1-year-old date palm plants. The petioles of 3 older leaves per plant were wounded by pricking the epidermis of the leaf with a needle (ca 20 pricks per petiole) and inoculated with agar discs from a 4-day-old PDA culture of the fungus. The control consisted of 4 mock-inoculated plants by placing plain PDA on the wounds of leaf petioles. Five weeks after inoculation, all the inoculated leaves showed symptoms of black scorch, petiole rot, and leaf necrosis, which were the same as those symptoms observed on the original diseased trees, while the controls did not show any symptoms. The fungus was re-isolated and confirmed as N. phoenicum by morphology. N. phoenicum has been reported to cause leaf spot, shoots blights, stalk and root rots as well as black scorch on different palm species all over the world. However, to our knowledge, this is the first report of N. phoenicum causing black scorch and rot disease in Arizona. The possible spread of N. phoenicum could have a significant economic impact and requires immediate attention through suitable disease management initiatives.

2.
Plant Dis ; 2021 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-33673768

RESUMO

Arizona is one of the largest producers of premium lemons for fresh market in the world. In 2018, 54,000 metric tons of lemons were produced on more than 7,300 acres. In recent years, wood rot diseases have become increasingly important in desert citrus production, with an incidence rate of 70 to 100% in some lemon orchards in Yuma, and lower rates in lemon orchards in the California desert. In 2018 and 2019, A brown wood rot showing symptoms of leaf chlorosis, branch gummosis and wilt, and branch breakage was the most common disease in many lemon orchards. Where disease was observed, a white mycelial mass often covered split exposed internal wood and basidiocarps were found on fallen decaying wood on orchard floors. The fungal colony, consistently isolated from decaying wood on malt extract agar or potato dextrose agar (PDA), was white, dense, and cottony-floccose. The 7-day-old culture had a distinct mushroom odor and hyphae were hyaline, thin-walled, and clamped generative. Genomic DNA was extracted from the mycelia of three isolates using DNeasy Plant Pro Kit (Qiagen Inc., Valencia, CA) according to the manufacturer's instructions. The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 (White et al., 1990). The resulting three nucleotide sequences were identical and deposited under accession number MW221272 in GenBank. A BLASTn search revealed 97.45% and 99.94% match with sequences HQ248221.1 and KT718002.1, respectively, which were isolates of Fomitopsis meliae with a query coverage at 100%. To fulfill Koch's postulates, pathogenicity tests were conducted on 30-year-old 'Lisbon' (Citrus x limon (L.) Osbeck) lemon trees at the Yuma Agriculture Center Mesa farm from February to July in 2019: ten branches (6-to-10 cm in diameter) from ten different trees were inoculated with each of three representative isolates. The inoculum was prepared by growing each isolate on wheat grains for three weeks at 23 to 25oC. Tree branches were inoculated by inserting five colonized wheat grains in 2-cm holes which were drilled into the branches and then covered with Parafilm. Five branches were inoculated with sterile grains and used as a control. Disease was assessed four months later by removing inoculated branches, splitting them in half through the inoculation point, and measuring the length of the wood area affected by wood rot. Brown discoloration of the wood extended an average of 3.9, 4.2, and 4.9 cm per isolate into wood tissues surrounding the inoculation hole, while control branches remained healthy. Fomitopsis meliae was consistently re-isolated from decayed wood based on morphology and ITS sequences. To our knowledge, this is the first report of brown wood rot caused by Fomitopsis meliae in lemon in Arizona and California. Fomitopsis species often attack conifers, hardwoods, and fruit trees (Adaskaveg et al., 1993, Gilbertson & Ryvarden, 1987). A species of Fomitopsis was detected in 40-year-old sweet orange trees and was highly pathogenic on lemons in southern Italy (Roccotelli et al., 2014). The ITS sequence of this Fomitopsis species (HM126455.1) shared 99% identity with those of Fomitopsis palustris (KJ995920.1) or F. ostreiformis (KC595918.1), but only 93.2% identity with that of F. meliae isolates identified in this study. Fomitopsis meliae can cause substantial pre-mature mortality of lemon trees and represents a major threat to the survival and profitability of lemon production in Arizona.

3.
Proc Natl Acad Sci U S A ; 113(52): 14958-14963, 2016 12 27.
Artigo em Inglês | MEDLINE | ID: mdl-27956644

RESUMO

Policy makers around the world tout decentralization as an effective tool in the governance of natural resources. Despite the popularity of these reforms, there is limited scientific evidence on the environmental effects of decentralization, especially in tropical biomes. This study presents evidence on the institutional conditions under which decentralization is likely to be successful in sustaining forests. We draw on common-pool resource theory to argue that the environmental impact of decentralization hinges on the ability of reforms to engage local forest users in the governance of forests. Using matching techniques, we analyze longitudinal field observations on both social and biophysical characteristics in a large number of local government territories in Bolivia (a country with a decentralized forestry policy) and Peru (a country with a much more centralized forestry policy). We find that territories with a decentralized forest governance structure have more stable forest cover, but only when local forest user groups actively engage with the local government officials. We provide evidence in support of a possible causal process behind these results: When user groups engage with the decentralized units, it creates a more enabling environment for effective local governance of forests, including more local government-led forest governance activities, fora for the resolution of forest-related conflicts, intermunicipal cooperation in the forestry sector, and stronger technical capabilities of the local government staff.


Assuntos
Relações Comunidade-Instituição , Conservação dos Recursos Naturais , Agricultura Florestal/legislação & jurisprudência , Governo Local , Bolívia , Ecossistema , Florestas , Humanos , Peru , Política Pública , Árvores
4.
J Strength Cond Res ; 33(7): 1745-1754, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31145385

RESUMO

Kildow, AR, Wright, G, Reh, RM, Jaime, S, and Doberstein, S. Can monitoring training load deter performance drop-off during off-season training in Division III American football players? J Strength Cond Res 33(7): 1745-1754, 2019-The primary aim of this observational investigation was to monitor performance of Division III American football players during off-season training while the secondary aim was to investigate differences in training adaptations between linemen and nonline players. Twenty-three subjects from the university's football team were recruited from an Exercise Science 100 conditioning class to participate in a 15-week off-season training program. Phase I consisted of concurrent strength and speed/endurance training (3-4 d·wk) for 7 weeks. Phase II consisted of strength training and spring football practice (3-4 d·wk) for 4 weeks. Countermovement jump, estimated one repetition maximum (1RM) bench press and back squat, 505 change of direction (COD), repeated 30-yard anaerobic sprint test (RAST), and body mass were all measured Pre, Mid, and Post training program. Two-way analysis of variance with repeated measures revealed no significant interaction between linemen and nonline players for all performance variables (p > 0.05). Over the course of the study, RSAT % decrement, 505 COD times, and estimated 1RM performance for bench and squat significantly improved (p ≤ 0.05). No significant changes were detected in CMJ, RSAT best time, or body mass. Results indicate that linemen and non-line players did not respond significantly different to the present training program. The 15-week training program produced improvements in COD skill, speed, anaerobic capacity, and muscular strength. Furthermore, all performance changes were maintained through the end of the study. Data from this study indicate that monitoring training load can give feedback to help augment performance and prevent performance decrements during the off-season.


Assuntos
Desempenho Atlético/fisiologia , Futebol Americano/fisiologia , Força Muscular/fisiologia , Resistência Física/fisiologia , Treinamento Resistido/métodos , Adaptação Fisiológica , Atletas , Índice de Massa Corporal , Aptidão Cardiorrespiratória/psicologia , Humanos , Masculino , Músculo Esquelético/fisiologia , Estações do Ano , Estados Unidos , Universidades , Adulto Jovem
5.
J Strength Cond Res ; 32(2): 482-489, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29084093

RESUMO

Jagim, AR, Dominy, TA, Camic, CL, Wright, G, Doberstein, S, Jones, MT, and Oliver, JM. Acute effects of the elevation training mask on strength performance in recreational weightlifters. J Strength Cond Res 32(2): 482-489, 2018-The Elevation Training Mask 2.0 (ETM) is a novel device that purportedly simulates altitude training. The purpose of this study was to investigate the acute effects of the ETM on resistance exercise performance, metabolic stress markers, and ratings of mental fatigue. Twenty male recreational weight lifters completed 2 training sessions of back squat and bench press (6 sets of 10 repetitions at 85% of 5-repetition maximum and seventh set to failure) as well as a maximal effort sprint test (18% body mass) with the mask (ETM) and without the mask (NM). Training evaluation included baseline and postexercise blood lactate and oxygen saturation measures. Performance evaluation included peak and average velocity bar velocity, total volume load, total work, total repetitions completed, and sprint performance. Adverse side effects were reported in 12% (n = 3) of participants, which included feelings of light headedness, anxiety, and discomfort. No differences were found in repetitions or total workload in back squat (p = 0.07) or bench press (p = 0.08) between conditions. A lower peak velocity was identified during the back squat, bench press, and sprint test in the ETM condition (p = 0.04). Blood lactate values were lower after bench press and sprint during the ETM condition (p < 0.001). Significantly lower ratings of alertness and focus for task were found after squat, bench press, and sprint test in the ETM condition compared with the NM condition (p < 0.001). Wearing the ETM during bouts of resistance training did not hinder the ability to achieve desired training volumes during the resistance training session. However, wearing the ETM does seem to attenuate the ability to maintain working velocity during training bouts and negatively influence ratings of alertness and focus for task.


Assuntos
Altitude , Máscaras , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Oxigênio/sangue , Treinamento Resistido/instrumentação , Levantamento de Peso/fisiologia , Dorso/fisiologia , Estudos Cross-Over , Humanos , Ácido Láctico/sangue , Masculino , Resistência Física/efeitos dos fármacos , Levantamento de Peso/psicologia , Adulto Jovem
6.
Ecology ; 98(6): 1513-1523, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28558159

RESUMO

Understanding plant community succession is one of the original pursuits of ecology, forming some of the earliest theoretical frameworks in the field. Much of this was built on the long-term research of William S. Cooper, who established a permanent plot network in Glacier Bay, Alaska, in 1916. This study now represents the longest-running primary succession plot network in the world. Permanent plots are useful for their ability to follow mechanistic change through time without assumptions inherent in space-for-time (chronosequence) designs. After 100-yr, these plots show surprising variety in species composition, soil characteristics (carbon, nitrogen, depth), and percent cover, attributable to variation in initial vegetation establishment first noted by Cooper in the 1916-1923 time period, partially driven by dispersal limitations. There has been almost a complete community composition replacement over the century and general species richness increase, but the effective number of species has declined significantly due to dominance of Salix species which established 100-yr prior (the only remaining species from the original cohort). Where Salix dominates, there is no establishment of "later" successional species like Picea. Plots nearer the entrance to Glacier Bay, and thus closer to potential seed sources after the most recent glaciation, have had consistently higher species richness for 100 yr. Age of plots is the best predictor of soil N content and C:N ratio, though plots still dominated by Salix had lower overall N; soil accumulation was more associated with dominant species. This highlights the importance of contingency and dispersal in community development. The 100-yr record of these plots, including species composition, spatial relationships, cover, and observed interactions between species provides a powerful view of long-term primary succession.


Assuntos
Ecologia , Alaska , Baías , Camada de Gelo , Solo
7.
J Strength Cond Res ; 31(2): 539-547, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27227795

RESUMO

Lockie, RG, Jalilvand, F, Orjalo, AJ, Giuliano, DV, Moreno, MR, and Wright, GA. A methodological report: Adapting the 505 change-of-direction speed test specific to American football. J Strength Cond Res 31(2): 539-547, 2017-The 505 involves a 10-m sprint past a timing gate, followed by a 180° change-of-direction (COD) performed over 5 m. This methodological report investigated an adapted 505 (A505) designed to be football-specific by changing the distances to 10 and 5 yd. Twenty-five high school football players (6 linemen [LM]; 8 quarterbacks, running backs, and linebackers [QB/RB/LB]; 11 receivers and defensive backs [R/DB]) completed the A505 and 40-yd sprint. The difference between A505 and 0 to 10-yd time determined the COD deficit for each leg. In a follow-up session, 10 subjects completed the A505 again and 10 subjects completed the 505. Reliability was analyzed by t-tests to determine between-session differences, typical error (TE), and coefficient of variation. Test usefulness was examined via TE and smallest worthwhile change (SWC) differences. Pearson's correlations calculated relationships between the A505 and 505, and A505 and COD deficit with the 40-yd sprint. A 1-way analysis of variance (p ≤ 0.05) derived between-position differences in the A505 and COD deficit. There were no between-session differences for the A505 (p = 0.45-0.76; intraclass correlation coefficient = 0.84-0.95; TE = 2.03-4.13%). Additionally, the A505 was capable of detecting moderate performance changes (SWC0.5 > TE). The A505 correlated with the 505 and 40-yard sprint (r = 0.58-0.92), suggesting the modified version assessed similar qualities. Receivers and defensive backs were faster than LM in the A505 for both legs, and right-leg COD deficit. Quarterbacks, running backs, and linebackers were faster than LM in the right-leg A505. The A505 is reliable, can detect moderate performance changes, and can discriminate between football position groups.


Assuntos
Desempenho Atlético/fisiologia , Futebol Americano/fisiologia , Corrida/fisiologia , Adolescente , Estudos Transversais , Humanos , Perna (Membro)/fisiologia , Masculino , Reprodutibilidade dos Testes
8.
J Strength Cond Res ; 29(5): 1295-301, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25426514

RESUMO

The purpose of this study was to investigate the effect of various loads on the force-time characteristics associated with peak power during the hang high pull (HHP). Fourteen athletic men (age: 21.6 ± 1.3 years; height: 179.3 ± 5.6 cm; body mass: 81.5 ± 8.7 kg; 1 repetition maximum [1RM] hang power clean [HPC]: 104.9 ± 15.1 kg) performed sets of the HHP at 30, 45, 65, and 80% of their 1RM HPC. Peak force, peak velocity, peak power, force at peak power, and velocity at peak power were compared between loads. Statistical differences in peak force (p = 0.001), peak velocity (p < 0.001), peak power (p = 0.015), force at peak power (p < 0.001), and velocity at peak power (p < 0.001) existed, with the greatest values for each variable occurring at 80, 30, 45, 80, and 30% 1RM HPC, respectively. Effect sizes between loads indicated that larger differences in velocity at peak power existed as compared with those displayed by force at peak power. It seems that differences in velocity may contribute to a greater extent to differences in peak power production as compared with force during the HHP. Further investigation of both force and velocity at peak power during weightlifting variations is necessary to provide insight on the contributing factors of power production. Specific load ranges should be prescribed to optimally train the variables associated with power development during the HHP.


Assuntos
Músculo Esquelético/fisiologia , Treinamento Resistido/métodos , Levantamento de Peso/fisiologia , Humanos , Masculino , Contração Muscular , Força Muscular , Fatores de Tempo , Adulto Jovem
9.
J Strength Cond Res ; 29(2): 451-7, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25072668

RESUMO

The purpose of this study was to develop and analyze a sport-specific conditioning test for wrestling that will incorporate the physiological demands of a match. Sixteen D-III collegiate wrestlers performed 2 tests to assess physical conditioning. The developed test (sandbag test) used a bag filled with sand that was repeatedly thrown over a course of seven 1-minute rounds. Average time per throw (T/T) was determined each round. The sandbag test was compared with a previously established repeated sprint protocol of maximal effort arm cranking on an upper body ergometer (UBE). Mean power output was determined for each sprint. Both the UBE test and the sandbag test were compared using performance decrement (%fatigue), blood lactate (BLa), and peak heart rate (HRpeak) values. Test-retest reliability for the sandbag test was found to be almost perfect using T/T (intraclass correlation coefficient, r = 0.96). No significant differences in %fatigue were found between the UBE test and the sandbag test (p = 0.600), BLa (p = 0.283), and HRpeak (p = 0.214). Further analysis by weight class (light-weight class [LWC] and heavy-weight class [HWC]) found a significant interaction for %fatigue between groups for the sandbag test and UBE (p = 0.001), but no interactions were observed for BLa (p = 0.198) or HRpeak (p = 0.990). Although no significant differences were found in %fatigue between the 2 tests when the data were grouped together, a clear difference was found between the LWC and HWC groups only in the sandbag test, indicating that this test may be more sensitive than the UBE. Coaches can assess their wrestlers with this reliable, inexpensive, and time-efficient sandbag test.


Assuntos
Teste de Esforço/métodos , Condicionamento Físico Humano/métodos , Luta Romana/fisiologia , Adulto , Limiar Anaeróbio/fisiologia , Ergometria , Fadiga/fisiopatologia , Frequência Cardíaca/fisiologia , Humanos , Reprodutibilidade dos Testes
10.
J Strength Cond Res ; 29(8): 2197-204, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25627645

RESUMO

The purpose of this study was to determine the test-retest reliability of a newly developed anaerobic sprint running test (ASRT) on a nonmotorized treadmill (NMT). Twenty-six collegiate male athletes (21.2 ± 2.1 years; 181.3 ± 6.5 cm; 79.0 ± 9.3 kg) completed 3 trials of a 25-second maximal effort sprint on an NMT against a workload set to 18% of their individual body mass. Anaerobic power was determined by relative peak power output (PP) and anaerobic capacity was determined by relative mean power output (MP) during the test. Blood lactate (BLa) responses and fatigue index (FI) were also determined. Test-retest reliability was assessed by intraclass correlation coefficients (ICCs) and coefficients of variation (CV%). Results indicated no significant difference between the 3 trials for PP (T1 = 29.95 ± 6.51 W·kg(-1), T2 = 28.57 ± 5.55 W·kg(-1), T3 = 29.47 ± 5.94 W·kg(-1)), MP (T1 = 20.97 ± 3.64 W·kg(-1), T2 = 20.50 ± 3.46 W·kg(-1), T3 = 21.17 ± 3.79 W·kg(-1), and FI (T1 = 55 ± 8%, T2 = 51 ± 8%, T3 = 52 ± 9%). Reliability between the 3 trials for PP (ICC: r = 0.96, CV: 7%) and MP (ICC: r = 0.97, CV: 6%) was considered high. Reliability for FI exhibited an ICC of r = 0.83 (CV: 6%). Postsprint BLa values were not significantly different (p = 0.49) between the 3 trials. Test-retest reliability for postsprint BLa was found to be good (r = 0.68, CV = 8.8%). The results of the study indicate that the ASRT is reliable for assessing PP and MP in highly motivated subjects. In addition, anaerobic testing using the ASRT may be a more sport-specific test to assess anaerobic performance for many coaches and athletes.


Assuntos
Limiar Anaeróbio , Teste de Esforço/métodos , Corrida/fisiologia , Teste de Esforço/instrumentação , Fadiga/fisiopatologia , Humanos , Ácido Láctico/sangue , Masculino , Reprodutibilidade dos Testes , Adulto Jovem
11.
J Strength Cond Res ; 28(4): 1113-8, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23838978

RESUMO

Three parallel squat protocols with equal total work volume were used to determine the metabolic response of resistance exercise with different practical training protocols combining program variables in the way that they are typically prescribed in field. Sixteen men able to back squat 1.5 times their body weight participated in the study. Individualized muscular endurance (ME), strength (STR), and hypertrophy (HYP) squat workouts were developed based on a 1 repetition maximum back squat. Each protocol was performed 3-7 days apart in random order. Venous blood was obtained after 5 minutes of seated rest both before and after each workout for ammonium and lactate analysis. The ME protocol (79.8 µM [SD = 45.4], 95% confidence interval [CI]: 55.7-104.0) produced a greater change of plasma ammonium than both the HYP (45.3 µM [SD = 34.5], 95% CI: 26.9-63.6, p = 0.017) and STR (31.7 µM [SD = 52.3], 95% CI: 3.9-59.6, p = 0.006) protocols. Change of blood lactate concentration from resting levels to postexercise levels was significantly different (p = 0.005) between ME (6.1 mM [SD = 2.9], 95% CI: 4.6-7.7) and STR (3.9 mM [SD = 2.5], 95% CI: 2.6-5.2) protocols. The main finding of this study is that blood ammonium and lactate seem to accumulate in response to an increasing number of repetitions with decreasing rest time between sets. As consequence, a greater number of repetitions should be added to a resistance workout, along with a shorter rest time between sets when training for events that induce a large metabolic load. The metabolic accumulation associated with high repetition exercise may represent the need for longer recovery time between these types of workouts compared with workouts using a low number of repetitions.


Assuntos
Compostos de Amônio/sangue , Ácido Láctico/sangue , Resistência Física/fisiologia , Treinamento Resistido/métodos , Adolescente , Compostos de Amônio/análise , Intervalos de Confiança , Exercício Físico/fisiologia , Humanos , Ácido Láctico/análise , Masculino , Contração Muscular/fisiologia , Força Muscular/fisiologia , Estudos de Amostragem , Levantamento de Peso/fisiologia , Adulto Jovem
12.
J Strength Cond Res ; 28(2): 350-60, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23689341

RESUMO

The purpose of this study was to compare the power production of the hang clean (HC), jump shrug (JS), and high pull (HP) when performed at different relative loads. Seventeen men with previous HC training experience, performed 3 repetitions each of the HC, JS, and HP at relative loads of 30, 45, 65, and 80% of their 1 repetition maximum (1RM) HC on a force platform over 3 different testing sessions. Peak power output (PPO), peak force (PF), and peak velocity (PV) of the lifter plus bar system during each repetition were compared. The JS produced a greater PPO, PF, and PV than both the HC (p < 0.001) and HP (p < 0.001). The HP also produced a greater PPO (p < 0.01) and PV (p < 0.001) than the HC. Peak power output, PF, and PV occurred at 45, 65, and 30% 1RM, respectively. Peak power output at 45% 1RM was greater than PPO at 65% (p = 0.043) and 80% 1RM (p = 0.004). Peak force at 30% was less than PF at 45% (p = 0.006), 65% (p < 0.001), and 80% 1RM (p = 0.003). Peak velocity at 30 and 45% was greater than PV at 65% (p < 0.001) and 80% 1RM (p < 0.001). Peak velocity at 65% 1RM was also greater than PV at 80% 1RM (p < 0.001). When designing resistance training programs, practitioners should consider implementing the JS and HP. To optimize PPO, loads of approximately 30 and 45% 1RM HC are recommended for the JS and HP, respectively.


Assuntos
Movimento/fisiologia , Força Muscular , Músculo Esquelético/fisiologia , Treinamento Resistido/métodos , Levantamento de Peso/fisiologia , Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Humanos , Cinética , Extremidade Inferior/fisiologia , Masculino , Adulto Jovem
13.
Sports Biomech ; 13(1): 87-95, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24968513

RESUMO

This study examined the impact of load on lower body performance variables during the hang power clean. Fourteen men performed the hang power clean at loads of 30%, 45%, 65%, and 80% 1RM. Peak force, velocity, power, force at peak power, velocity at peak power, and rate of force development were compared at each load. The greatest peak force occurred at 80% 1RM. Peak force at 30% 1RM was statistically lower than peak force at 45% (p = 0.022), 65% (p = 0.010), and 80% 1RM (p = 0.018). Force at peak power at 65% and 80% 1RM was statistically greater than force at peak power at 30% (p < 0.01) and 45% 1RM (p < 0.01). The greatest rate of force development occurred at 30% 1RM, but was not statistically different from the rate of force development at 45%, 65%, and 80% 1RM. The rate of force development at 65% 1RM was statistically greater than the rate of force development at 80% 1RM (p = 0.035). No other statistical differences existed in any variable existed. Changes in load affected the peak force, force at peak power, and rate of force development, but not the peak velocity, power, or velocity at peak power.


Assuntos
Levantamento de Peso/fisiologia , Adulto , Análise de Variância , Fenômenos Biomecânicos , Teste de Esforço , Humanos , Perna (Membro)/fisiologia , Masculino , Adulto Jovem
14.
J Strength Cond Res ; 27(2): 526-32, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22476168

RESUMO

Recent research has shown that beta-alanine (BA) supplementation can increase intramuscular carnosine levels. Carnosine is an intramuscular buffer, and it has been linked to improvements in performance, specifically during bouts of high-intensity exercise that are likely limited by muscle acidosis. Therefore, the purpose of this study was to examine the effect of BA supplementation on sprint endurance at 2 different supramaximal intensities. Twenty-one anaerobically trained (rugby players [n = 4], wrestlers [n = 11], and recreationally strength trained athletes [n = 6]) college-aged men participated in a double-blind, placebo controlled study. The subjects performed an incremental VO2max test and 2 sprint to exhaustion tests set at 115 and 140% of their VO2max on a motorized treadmill before (PRE) and after (POST) a 5-week supplementation period. During this time, the subjects ingested either a BA supplement or placebo (PLA) with meals. The subjects ingested 4 g·d(-1) of BA or PLA during the first week and 6 g·d(-1) the following 4 weeks. Capillary blood samples were taken before and after each sprint to determine blood lactate response to the sprint exercise. No significant group (BA, PLA) × intensity (115%, 140%; p = 0.60), group by time (PRE, POST; p = 0.72), or group × intensity × time (p = 0.74) interactions were observed for time to exhaustion. In addition, similar nonsignificant observations were made for lactate response to the sprints (group × intensity, p = 0.43; group × time, p = 0.33, group × intensity × time, p = 0.56). From the results of this study, it was concluded that beta-alanine supplementation did not have a significant effect on sprint endurance at supramaximal intensities.


Assuntos
Suplementos Nutricionais , Tolerância ao Exercício/efeitos dos fármacos , Corrida/fisiologia , beta-Alanina/farmacologia , Adolescente , Adulto , Método Duplo-Cego , Teste de Esforço , Humanos , Ácido Láctico/sangue , Masculino , Consumo de Oxigênio , Fatores de Tempo , Adulto Jovem
16.
PLoS One ; 18(2): e0272366, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36730172

RESUMO

We present the results of a hybrid research design that borrows from both experimental techniques-experimental games-and observational techniques-surveys-to examine the relationships between basic human values and exposure to natural ecosystems, on the one hand, and collective action for resource governance, on the other. We initially hypothesize that more frequent exposure to forests, and more pro-environmental values will be associated with more conservation action. However, we find that other values-tradition and conformity-are more important than pro-environmental values or exposure to nature. Our results imply that resource governance is likely to be more successful where resource users hold values that facilitate cooperation, not necessarily strong pro-environmental values.


Assuntos
Conservação dos Recursos Naturais , Ecossistema , Humanos , Conservação dos Recursos Naturais/métodos , Comportamento Social , Florestas
17.
Am J Public Health ; 102(5): 833-5, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22420808

RESUMO

Because of the rapid development of genital warts (GW) after infection, monitoring GW trends may provide early evidence of population-level human papillomavirus (HPV) vaccine effectiveness. Trends in GW diagnoses were assessed using public family planning administrative data. Between 2007 and 2010, among females younger than 21 years, these diagnoses decreased 35% from 0.94% to 0.61% (P(trend) < .001). Decreases were also observed among males younger than 21 years (19%); and among females and males ages 21-25 (10% and 11%, respectively). The diagnoses stabilized or increased among older age groups. HPV vaccine may be preventing GW among young people.


Assuntos
Condiloma Acuminado/epidemiologia , Condiloma Acuminado/prevenção & controle , Revisão da Utilização de Seguros/estatística & dados numéricos , Vacinas contra Papillomavirus/administração & dosagem , Adolescente , Adulto , Fatores Etários , California/epidemiologia , Criança , Feminino , Humanos , Masculino , Vacinas contra Papillomavirus/uso terapêutico , Adulto Jovem
18.
J Strength Cond Res ; 26(3): 648-55, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22173625

RESUMO

The purpose of this study was to determine the efficacy of estimating peak lower body power from a maximal jump squat using 3 different vertical jump prediction equations. Sixty physically active college students (30 men, 30 women) performed jump squats with a weighted bar's applied load of 20, 40, and 60% of body mass across the shoulders. Each jump squat was simultaneously monitored using a force plate and a contact mat. Peak power (PP) was calculated using vertical ground reaction force from the force plate data. Commonly used equations requiring body mass and vertical jump height to estimate PP were applied such that the system mass (mass of body + applied load) was substituted for body mass. Jump height was determined from flight time as measured with a contact mat during a maximal jump squat. Estimations of PP (PP(est)) for each load and for each prediction equation were compared with criterion PP values from a force plate (PP(FP)). The PP(est) values had high test-retest reliability and were strongly correlated to PP(FP) in both men and women at all relative loads. However, only the Harman equation accurately predicted PP(FP) at all relative loads. It can therefore be concluded that the Harman equation may be used to estimate PP of a loaded jump squat knowing the system mass and peak jump height when more precise (and expensive) measurement equipment is unavailable. Further, high reliability and correlation with criterion values suggest that serial assessment of power production across training periods could be used for relative assessment of change by either of the prediction equations used in this study.


Assuntos
Desempenho Atlético/fisiologia , Movimento/fisiologia , Força Muscular/fisiologia , Peso Corporal/fisiologia , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes , Fatores Sexuais
19.
Int J Sports Physiol Perform ; 17(5): 687-693, 2022 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-35158324

RESUMO

INTRODUCTION: The relationship between the percentage of a fatiguing ambulatory task completed and rating of perceived exertion (RPE) appears to be linear and scalar, with a relatively narrow "window." Recent evidence has suggested that a similar relationship may exist for muscularly demanding tasks. METHODS: To determine whether muscularly demanding tasks fit within this "ambulatory window," we tested resistance-trained athletes performing bench press and leg press with different loadings predicted to allow 5, 10, 20, and 30 repetitions and measured RPE (category ratio scale) at the end of the concentric action for each repetition. RESULTS: There was a regular, and strongly linear, pattern of growth of RPE for both bench press (r = .89) and leg press (r = .90) during the tasks that allowed 5.2 (1.2), 11.6 (1.9), 22.7 (2.0), and 30.8 (3.2) repetitions for bench press and 5.5 (1.5), 11.4 (1.6), 20.2 (3.0), and 32.4 (4.2) repetitions for leg press, respectively. CONCLUSIONS: The path of the RPE growth versus percentage task fit within the window evident for ambulatory tasks. The results suggest that the RPE versus percentage task completed relationship is scalar, relatively linear, and apparently independent of exercise mode.


Assuntos
Esforço Físico , Treinamento Resistido , Atletas , Exercício Físico , Humanos , Fadiga Muscular , Treinamento Resistido/métodos , Levantamento de Peso
20.
J Strength Cond Res ; 25(1): 94-102, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20093969

RESUMO

Our purpose was to provide an in-depth investigation of 2 commonly used depth jump variants: depth jumping over a hurdle and depth jumping while touching as high as possible using an overhead goal. Fourteen male athletes performed a series of depth jumps from a 45-cm box. Three types of jumping conditions were used. One type of depth jump was a control jump (DJ45-C), performed for maximal height with no external apparatus used to influence the jump. Another type of depth jump was performed over a hurdle (DJ45-H), which was set at an individualized height for each athlete based on their leaping ability. The final type of depth jump was performed for maximal touch height on a Vertec measuring device (DJ45-T). Timing, kinematics, and kinetics of the 3 jumping conditions were compared. The hurdle depth jumping condition demonstrated lower ground contact times and significantly less (p < 0.05) flexion in the hips (41.22 ± 8.10 degrees) and knees (67.47 ± 8.36 degrees) when compared to control (49.26 ± 10.90 degrees of hip flexion and 73.85 ± 10.68 degrees of knee flexion) and target (50.51 ± 9.51 degrees of hip flexion and 75.01 ± 9.97 degrees of knee flexion) conditions. Jumping conditions that used goals (DJ45-H, DJ45-T) produced significantly higher (p < 0.05) vertical velocity of the sacrum at toe-off (3.57 ± .34 m/s and 3.46 ± .36 m/s, respectively) than the control condition (3.32 ± .34 m/s). The hurdle depth jump condition had higher ground reaction forces (875.36 ± 135.66 N) and higher dorsiflexion (566.02 ± 402.45 W) and plantar flexion power (768.84 ± 192.19 W) at the ankle than the Vertec (409.83 ± 387.23 W for dorsiflexion and 622.54 ± 188.95 W for plantar flexion) and control conditions (425.60 ± 380.01 W for dorsiflexion and 643.35 ± 166.70 W for plantar flexion). Few differences were found to exist between the Vertec and control conditions. Hurdle jumping in particular may be superior for the development of short ground contact time (<0.3 s) sport movements requiring brief but powerful lower-extremity power production.


Assuntos
Atletas , Desempenho Atlético , Tornozelo/fisiologia , Fenômenos Biomecânicos/fisiologia , Quadril/fisiologia , Humanos , Joelho/fisiologia , Masculino , Movimento/fisiologia , Adulto Jovem
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