Time-varying analysis of electrodermal activity during exercise.

The electrodermal activity (EDA) is a useful tool for assessing skin sympathetic nervous activity. Using spectral analysis of EDA data at rest, we have previously found that the spectral band which is the most sensitive to central sympathetic control is largely confined to 0.045 to 0.25 Hz. However, the frequency band associated with sympathetic control in EDA has not been studied for exercise conditions. Establishing the band limits more precisely is important to ensure the accuracy and sensitivity of the technique. As exercise intensity increases, it is intuitive that the frequencies associated with the autonomic dynamics should also increase accordingly. Hence, the aim of this study was to examine the appropriate frequency band associated with the sympathetic nervous system in the EDA signal during exercise. Eighteen healthy subjects underwent a sub-maximal exercise test, including a resting period, walking, and running, until achieving 85% of maximum heart rate. Both EDA and ECG data were measured simultaneously for all subjects. The ECG was used to monitor subjects' instantaneous heart rate, which was used to set the experiment's end point. We found that the upper bound of the frequency band (Fmax) containing the EDA spectral power significantly shifted to higher frequencies when subjects underwent prolonged low-intensity (Fmax ~ 0.28) and vigorous-intensity exercise (Fmax ~ 0.37 Hz) when compared to the resting condition. In summary, we have found shifting of the sympathetic dynamics to higher frequencies in the EDA signal when subjects undergo physical activity.

Case Study: Impact of Inter- and Intra-Day Energy Parameters on Bone Health, Menstrual Function, and Hormones in an Elite Junior Female Triathlete.

This observational case study examined the association of inter- and intraday energy intake and exercise energy expenditure with bone health, menstrual status and hematological factors in a female triathlete. The study spanned 7 months whereby energy intake and exercise energy expenditure were monitored three times (13 d); 16 blood samples were taken, urinary hormones were assessed for 3 months, and bone mineral density was measured twice. Energy availability tended to be sustained below 30 kcal/kg FFM/d and intraday energy intake patterns were often "back-loaded" with approximately 46% of energy consumed after 6 p.m. Most triiodothyronine values were low (1.1-1.2nmol/L) and supportive of reduced energy availability. The athlete had suppressed estradiol (105.1 ± 71.7pmol/L) and progesterone (1.79 ±1.19nmol/L) concentrations as well as urinary sex-steroid metabolites during the entire monitoring period. Lumbar spine (L1-L4) bone mineral density was low (age-matched Z-score -1.4 to -1.5). Despite these health related maladies the athlete was able to perform typical weekly training loads (swim: 30-40 km, bike: 120-300 km, run 45-70 km) and was competitive as indicated by her continued improvement in ITU World Ranking during and beyond the assessment period. There is a delicate balance between health and performance that can become blurred especially for endurance athletes. Education (athletes, coaches, parents) and continued monitoring of specific indicators will enable evidence-based recommendations to be provided and help reduced the risk of health related issues while maximizing performance gains. Future research needs to longitudinally examine how performance on standardized tests in each discipline (e.g., 800-m swim, 20-km time trial, 5-km run) is impacted when aspects of the female athlete triad are present.

Ovarian suppression impairs sport performance in junior elite female swimmers.

INTRODUCTION: Competitive female athletes restrict energy intake and increase exercise energy expenditure frequently resulting in ovarian suppression. The purpose of this study was to determine the impact of ovarian suppression and energy deficit on swimming performance (400-m swim velocity). METHODS: Menstrual status was determined by circulating estradiol (E2) and progesterone (P4) in ten junior elite female swimmers (15-17 yr). The athletes were categorized as cyclic (CYC) or ovarian-suppressed (OVS). They were evaluated every 2 wk for metabolic hormones, bioenergetic parameters, and sport performance during the 12-wk season. RESULTS: CYC and OVS athletes were similar (P > 0.05) in age (CYC = 16.2 ± 1.8 yr, OVS = 17 ± 1.7 yr), body mass index (CYC = 21 ± 0.4 kg·m, OVS = 25 ± 0.8 kg·m), and gynecological age (CYC = 2.6 ± 1.1 yr, OVS = 2.8 ± 1.5 yr). OVS had suppressed P4 (P < 0.001) and E2 (P = 0.002) across the season. Total triiodothyronine (TT3) and insulin-like growth factor (IGF-1) were lower in OVS (TT3: CYC = 1.6 ± 0.2 nmol·L, OVS = 1.4 ± 0.1 nmol·L, P < 0.001; IGF-1: CYC = 243 ± 1 µg·mL, OVS = 214 ± 3 µg·mL P < 0.001) than CYC at week 12. Energy intake (P < 0.001) and energy availability (P < 0.001) were significantly lower in OVS versus CYC. OVS exhibited a 9.8% decline in Δ400-m swim velocity compared with an 8.2% improvement in CYC at week 12. CONCLUSIONS: Ovarian steroids (P4 and E2), metabolic hormones (TT3 and IGF-1), and energy status markers (EA and EI) were highly correlated with sport performance. This study illustrates that when exercise training occurs in the presence of ovarian suppression with evidence for energy conservation (i.e., reduced TT3), it is associated with poor sport performance. These data from junior elite female athletes support the need for dietary periodization to help optimize energy intake for appropriate training adaptation and maximal sport performance.

Exercise as an adjunct treatment for opiate agonist treatment: review of the current research and implementation strategies.

Opiate dependence is a significant public health concern linked to poor quality of life, comorbid psychiatric disorders, and high costs to society. Current opiate agonist treatments are an effective but limited intervention. Adjunctive interventions could improve and augment opiate agonist treatment outcomes, including drug abstinence, quality of life, and physical health. This article reviews exercise as an adjunctive intervention for opiate agonist treatment, especially in regards to improving mood and overall quality of life, while reducing other substance use. Poor adherence and dropout frequently prevent many individuals from garnering the many physical and mental health benefits of exercise. Strategies for implementing an exercise intervention, including safety considerations, are discussed.

Elevated PYY is associated with energy deficiency and indices of subclinical disordered eating in exercising women with hypothalamic amenorrhea.

The purpose of this study was twofold: (1) to determine if gastrointestinal hormones, associated with energy intake and energy balance, are altered in exercising women with hypothalamic amenorrhea and (2) to assess the association between gastrointestinal hormones and behavioural indicators of subclinical disordered eating in exercising women with hypothalamic amenorrhea. This cross-sectional study analyzed serum ghrelin, peptide YY (PYY), glucagon-like peptide-1 (GLP-1), menstrual status (by E1G and PdG), resting energy expenditure (REE), and subclinical eating behaviours in sedentary ovulatory (SedOv), exercising ovulatory (ExOv), and exercising amenorrheic (ExAmen) women. Groups were similar with respect to age (23.8+/-0.6 years) and BMI (21.4+/-0.3 kg/m(2)). The ratio of REE to predicted REE (REE:predicted REE) was 0.94+/-0.02, 0.94+/-0.02, and 0.88+/-0.02 in the SedOv, ExOv, and ExAmen groups, respectively. The REE:predicted REE in the ExAmen group was consistent with an energy deficiency. LogPYY, ghrelin, dietary cognitive restraint, and drive for thinness were elevated in the ExAmen group compared to other groups. GLP-1 concentrations were similar among groups. LogPYY correlated with drive for thinness and REE/FFM. In conclusion, fasting PYY and ghrelin concentrations are elevated in exercising women with FHA and both gastrointestinal peptides may serve as a proxy indicator of energy deficiency in this population.

Short-term response of bone turnover to low-dose oral contraceptives in exercising women with hypothalamic amenorrhea.

BACKGROUND: We examined the response of bone turnover markers and indices of energy status after 2 weeks of oral contraceptive (OC) therapy in premenopausal women with exercise-associated menstrual disturbances (EAMD). STUDY DESIGN: Six women with EAMD received one 28-day cycle of a triphasic OC containing 180-250 mcg norgestimate/25 mcg ethinyl estradiol (EAMD+OC) and six were controls (EAMD controls). Bone turnover markers amino-terminal propeptide of Type I procollagen and serum carboxy-terminal telopeptides of Type I collagen (PINP and SCTX-I) were assessed at baseline and after 2 weeks of OC therapy (EAMD+OC) or after a 30-day monitoring period (EAMD controls). Total triiodothyronine, resting energy expenditure (REE) and dietary intake were assessed as secondary end points. The absolute and percent changes from baseline in the primary and secondary outcomes were evaluated using an analysis of covariance, adjusting for baseline values of the corresponding outcome. RESULTS: Compared to EAMD controls, a significant change from baseline was observed in the EAMD+OC group for PINP (mean+/-SEM, 9.9+/-6.1 vs. -33.9+/-9.0 mcg/L; p=.005) and SCTX-I (-0.02+/-0.11 vs. -0.25+/-0.07 ng/mL; p=.017), but not osteoprotegerin (-0.53+/-0.22 vs. 0.20+/-0.44 pmol/L; p=.429) after 2 weeks (14.7+/-0.3 days) of OC therapy. Total triiodothyronine levels were elevated in the EAMD+OC group after therapy compared with EAMD controls (19.7+/-4.1 vs. -8.4+/-4.9 ng/dL; p=.002); however, no differences between groups were observed for the changes in REE or dietary intake. CONCLUSION: Our data demonstrate that 2 weeks of low-dose OC therapy rapidly reduced markers of bone resorption and formation, without any significant impact on energy status in women with EAMD.

Severity of energy-related menstrual disturbances increases in proportion to indices of energy conservation in exercising women.

Alterations in resting energy expenditure and metabolic hormones (energy conservation) are evident in increasing magnitude across a continuum of increasing severity of clinical menstrual disturbances, including luteal-phase defects, anovulation, and amenorrhea in exercising women. These data provide further evidence of the tight association between energy balance and reproduction and suggest that subtle declines in energy availability can produce clinically recognized menstrual disturbances.

Female athletes: factors impacting successful performance.

Competitive female athletes face many challenges unlike their recreationally active counterparts. As sport has advanced for girls and women, the physical, psychologic, and nutritional demands force female athletes to develop optimal strategies for competitive success. Sports medicine professionals must consume volumes of research investigating issues regarding competitive female athletes. This review focuses on three primary factors associated with females and performance: iron status, interrelated biorhythms, and energy optimization. Consideration of these factors in both health and performance goals is critical to the long-term success of competitive female athletes.

Effects of chromium supplementation on glycogen synthesis after high-intensity exercise.

PURPOSE: Chromium enhances insulin signaling and insulin-mediated glucose uptake in cultured cells. We investigated the effect of chromium on glycogen synthesis and insulin signaling in humans. METHODS: Sixteen overweight men (BMI = 31.1 +/- 3.0 kg.m) were randomly assigned to supplement with 600 microg.d chromium as picolinate (Cr; N = 8) or a placebo (Pl; N = 8). After 4 wk of supplementation, subjects performed a supramaximal bout of cycling exercise to deplete muscle glycogen, which was followed by high-glycemic carbohydrate feedings for the next 24 h. Muscle biopsies were obtained at rest, immediately after exercise, and 2 and 24 h after exercise. RESULTS: Elevations in glucose and insulin during recovery were not different, but the lactate response was significantly higher in Cr. There was a significant depletion in glycogen immediately after exercise, an increase at 2 h, and a further increase above rest at 24 h (P < 0.05). The rate of glycogen synthesis during the 2 h after exercise was not different between groups (Cr: 25.8 +/- 8.0 and Pl: 17.1 +/- 4.7 mmol.kg.h). Glycogen synthase activity was significantly increased immediately after exercise in both groups. Muscle phosphatidylinositol 3-kinase (PI 3-kinase) activity decreased immediately after exercise and increased at 2 h (P < 0.05), with a trend for a lower PI 3-kinase response in Cr (P = 0.08). CONCLUSIONS: Chromium supplementation did not augment glycogen synthesis during recovery from high-intensity exercise and high-carbohydrate feeding, although there was a trend for lower PI 3-kinase activity.

Peak systolic blood pressure on a graded maximal exercise test and the blood pressure response to an acute bout of submaximal exercise.

Blood pressure (BP) is immediately reduced after aerobic exercise (postexercise hypotension [PEH]). Whether peak systolic BP on a maximal graded exercise stress test (GEST) relates to PEH is not known. This study examined associations between peak systolic BP on a GEST and PEH. Subjects were 50 men (mean +/- SEM age 43.8 +/- 1.3 years) with elevated BP (145.3 +/- 1.5/85.9 +/-1.1 mm Hg). Men completed a GEST and 3 experiments: nonexercise control and 2 cycle bouts at 40% (LIGHT) and 60% (MODERATE) of maximal oxygen consumption. After the experiments, subjects left the laboratory wearing ambulatory BP monitors. Peak systolic BP on a GEST was categorized into tertiles: low (n = 17, 197.4 +/- 2.0 mm Hg), medium (n = 16, 218.4 +/- 1.4 mm Hg), and high (n = 17, 248.9 +/- 2.8 mm Hg). Repeated-measures analysis of variance tested if BP differed over time and among experimental conditions and peak systolic BP groups. In men with high peak systolic BP, systolic BP was reduced by 7.3 +/- 2.6 mm Hg after LIGHT and by 5.0 +/- 2.2 mm Hg after MODERATE compared with nonexercise control over 10 hours, with the more apparent effects seen after LIGHT (p <0.05). In men with low peak systolic BP, systolic BP was reduced by 6.3 +/- 2.3 mm Hg after MODERATE compared with nonexercise control over 10 hours (p <0.05). In men with medium peak systolic BP, systolic BP was not different after exercise compared with nonexercise control over 10 hours (p >or=0.05). Men with high peak systolic BP had decreased systolic BP to the greatest extent after LIGHT, whereas men with low peak systolic BP reduced systolic BP after MODERATE. In conclusion, the findings of this study suggest that peak systolic BP on a GEST may be used to characterize which men with hypertension will have decreased systolic BP after acute submaximal aerobic exercise.

Pituitary-adrenal responses to arm versus leg exercise in untrained man.

The purpose of this study was to examine pituitary-adrenal (PA) hormone responses [beta-endorphin (beta-END), adrenocorticotropic hormone (ACTH) and cortisol] to arm exercise (AE) and leg exercise (LE) at 60 and 80% of the muscle-group specific VO2 peak. Eight healthy untrained men (AE VO2 peak=32.4+/-3.0 ml kg(-1) min(-1), LE VO2 peak=46.9+/-5.3 ml kg(-1) min(-1)) performed two sub-maximal AE and LE tests in random order. Plasma beta-END, ACTH and cortisol were not different (P>0.05) between AE and LE at either exercise intensity; the 60% testing elicited no changes from pre-exercise (PRE) values. For 80% testing, plasma beta-END, ACTH and cortisol were consistently, but not significantly, greater during LE than AE. In general, plasma beta-END and ACTH were higher (P<0.05) during 80% exercise, than PRE, for both AE and LE. Plasma cortisol was elevated (P<0.05) above PRE during 80% LE, and following 80% for both AE and LE. Plasma ACTH was higher (P<0.05) during 80% LE and AE versus 60% LE and AE, respectively. Plasma beta-END and cortisol were significantly higher during and immediately after 80% LE than 60% LE. Thus, plasma beta-END, ACTH and cortisol responses were similar for AE and LE at the two relative exercise intensities, with the intensity threshold occurring somewhere between 60 and 80% of VO2 peak. It appears that the smaller muscle mass associated with AE was sufficient to stimulate these PA axis hormones in a manner similar to LE, despite the higher metabolic stress (i.e., plasma La-) associated with LE.

Positional performance profiling of elite ice hockey players.

PURPOSE: The primary purpose of this study was to determine whether positional profiling is possible for elite ice hockey players by examining anthropometric characteristics and physiological performance. In addition, performance ranges and percentiles were determined for each position (forwards, defensemen, and goalkeepers) on all dependent variables. METHODS: A retrospective, cross-sectional study design was used with performance data from ice hockey players (mean age = 18.0 +/- 0.6 years) attending the 2001 (n = 74), 2002 (n = 84), and 2003 (n = 92) Combines. Four anthropometric characteristics and 12 performance tests were the dependent variables. A 3 x 3 (position x year) 2-way ANOVA was used to determine whether any significant interactions were present. No significant interactions were observed, so the data were collapsed over the 3-year period and positional characteristics were analyzed using a 1-way ANOVA. RESULTS: Defenders were heavier and/or taller compared with the other 2 positions (P

Off-ice performance and draft status of elite ice hockey players.

PURPOSE: The primary purpose of this study was to determine whether tests performed at the National Hockey League (NHL) Combine could distinguish draft status (ie, the round selected). A secondary aim was to provide performance ranges and percentiles for each of the dependent variables. METHODS: A retrospective, cross-sectional study design was used with performance data and draft order from 2001, 2002, and 2003 Combine participants. Draft round was divided into 5 classifications (rounds 1, 2, 3, 4, and 5 through 9), and performances on 12 physical tests served as dependent variables. Three multiple analyses of covariance (MANCOVAs) were used to determine the significance of performance scores at the NHL Combine on draft selection. Age (years), body mass (kg), height (cm), and percentage body fat were treated as covariates. RESULTS: Overall, MANCOVA results indicated no significant effect of performance on draft selection for 2001, 2002, or 2003. Subsequent univariate tests revealed that no single dependent variable was able to distinguish between draft rounds for any of the 3 years sampled. CONCLUSIONS: Using draft status as an indicator of ice hockey performance, it appears that off-ice tests cannot accurately predict ice hockey playing ability in an elite group of athletes. This might stem from homogeneity of the Combine participants, a lack of validity of the tests, or other factors (eg, on-ice hockey skills, psychological variables, etc) that play a role in draft selection.

Androgen receptor content following heavy resistance exercise in men.

The purpose of the present investigation was to examine androgen receptor (AR) content in the vastus lateralis following two resistance exercise protocols of different volume. Nine resistance-trained men (age=24.3+/-4.4 years) performed the squat exercise for 1 (SS) and 6 sets (MS) of 10 repetitions in a random, counter-balanced order. Muscle biopsies were performed at baseline, and 1h following each protocol. Blood was collected prior to, immediately following (IP), and every 15 min after each protocol for 1h. No acute elevations in serum total testosterone were observed following SS, whereas significant 16-23% elevations were observed at IP, 15, and 30 min post-exercise following MS. No acute elevations in plasma cortisol were observed following SS, whereas significant 31-49% elevations were observed for MS at IP, 15, and 30 min post-exercise. Androgen receptor content did not change 1h following SS but significantly decreased by 46% following MS. These results demonstrated that a higher volume of resistance exercise resulted in down-regulation of AR content 1h post-exercise. This may have been due to greater protein catabolism associated with the higher level of stress following higher-volume resistance exercise.

High-affinity growth hormone binding protein and acute heavy resistance exercise.

PURPOSE: The purpose of this investigation was to examine the influence of resistance training on circulating concentrations of growth hormone binding protein (GHBP) in response to acute heavy resistance exercise. METHODS: Using a cross-sectional experimental design, a group of resistance-trained men (RT, N=9, 7.9+/-1.3 yr resistance training experience) and a group of untrained men (UT, N=10) performed an acute heavy resistance exercise protocol (AHREP) consisting of 6 sets of 10 repetition maximum parallel squats. Blood samples were obtained 72 h before exercise, immediately before exercise, and 0, 15, 30, 45, and 60 min after exercise. RESULTS: Significant increases (P<0.05) in GHBP, immunoreactive growth hormone (iGH), and IGF-1 were observed in both subject groups after AHREP. There were no differences (P>0.05) between groups in GHBP at rest or after AHREP. However, RT exhibited a significantly greater iGH response to AHREP than UT subjects, and significantly higher IGF-1 values at rest and after exercise. Significant positive correlations were found between GHBP and BMI, body fat, and leptin in both groups. A significant positive correlation also was observed between resting leptin and GHBP values in UT but not RT subjects. CONCLUSIONS: In summary, these data indicate that resistance training does not increase blood GHBP. Nevertheless, the increases observed with IGF-1 concentrations in the resistance-trained subjects do suggest an apparent adaptation with the regulation of this hormone. If there was in fact an increase in GH sensitivity and GH receptor expression at the liver that was not detected by blood GHBP in this study, it may be possible that factors contributing to the circulating concentration of GHBP other than hepatocytes (e.g., leptin and adipocytes) may serve to mask training-induced increases in circulating GHBP of a hepatic origin, thus masking any detectable increase in GH receptor expression.

Diet and exercise for weight loss: a review of current issues.

Obesity is a fast growing epidemic that is primarily due to environmental influences. Nutrition and exercise represent modifiable factors with a major impact on energy balance. Despite considerable research, there remains continued debate regarding the energy content and the optimal macronutrient distribution for promoting healthy and effective weight loss. Low-fat diets have been advised for many years to reduce obesity. However, their effectiveness has been recently challenged, partly because the prevalence of obesity continues to rise despite reductions in fat intake. There are also concerns regarding the methodology of clinical trials showing benefits of fat reduction on weight loss. Although often viewed as a fad diet, very low-carbohydrate (ketogenic) diets are very popular and several recent clinical trials indicate they are more effective at promoting short-term weight loss and improving characteristics of the metabolic syndrome than low-fat diets. However, there is a need to obtain long-term safety and efficacy data. Clearly, weight loss can be achieved with a variety of diet interventions but the effects on other health-related aspects also need to be considered and studied in more detail. Exercise can have positive effects on weight loss, weight control and overall general health, although debate exists concerning the most effective mode, duration and intensity of exercise required to achieve these effects. Importantly, any effective weight control treatment must consider a life-long plan or there will likely be weight regain. Perhaps the most challenging, but rewarding, question that faces researchers is how to predict individual responses to diet and exercise interventions.

Heat acclimation and physical training adaptations of young women using different contraceptive hormones.

Although endogenous and exogenous steroid hormones affect numerous physiological processes, the interactions of reproductive hormones, chronic exercise training, and heat acclimation are unknown. This investigation evaluated the responses and adaptations of 36 inactive females [age 21 +/- 3 (SD) yr] as they undertook a 7- to 8-wk program [heat acclimation and physical training (HAPT)] of indoor heat acclimation (90 min/day, 3 days/wk) and outdoor physical training (3 days/wk) while using either an oral estradiol-progestin contraceptive (ORAL, n = 15), a contraceptive injection of depot medroxyprogesterone acetate (DEPO, n = 7), or no contraceptive (EU-OV, n = 14; control). Standardized physical fitness and exercise-heat tolerance tests (36.5 degrees C, 37% relative humidity), administered before and after HAPT, demonstrated that the three subject groups successfully (P < 0.05) acclimated to heat (i.e., rectal temperature, heart rate) and improved muscular endurance (i.e., sit-ups, push-ups, 4.6-km run time) and body composition characteristics. The stress of HAPT did not disrupt the menstrual cycle length/phase characteristics, ovulation, or plasma hormone concentrations of EU-OV. No between-group differences (P > 0.05) existed for rectal and skin temperatures or metabolic, cardiorespiratory, muscular endurance, or body composition variables. A significant difference post-HAPT in the onset temperature of local sweating, ORAL (37.2 +/- 0.4 degrees C) vs. DEPO (37.7 +/- 0.2 degrees C), suggested that steroid hormones influenced this adaptation. In summary, virtually all adaptations of ORAL and DEPO were similar to EU-OV, suggesting that exogenous reproductive hormones neither enhanced nor impaired the ability of women to complete 7-8 wk of strenuous physical training and heat acclimation.

Characteristics of elite open-water swimmers.

Open-water swimming (5, 10, and 25 km) has many unique challenges that separate it from other endurance sports, like marathon running and cycling. The characteristics of a successful open-water swimmer are unclear. The purpose of this study was to determine the physical and metabolic characteristics of a group of elite-level open-water swimmers. The open-water swimmers were participating in a 1-week training camp. Anthropometric, metabolic, and blood chemistry assessments were performed on the athletes. The swimmers had a VO(2)peak of 5.51 +/- 0.96 and 5.06 +/- 0.57 ml.kg(-1).min(-1) for males and females, respectively. Their lactate threshold (LT) occurred at a pace equal to 88.75% of peak pace for males and 93.75% for females. These elite open-water swimmers were smaller and lighter than competitive pool swimmers. They possess aerobic metabolic alterations that resulted in enhanced performance in distance swimming. Trainers and coaches should develop dry-land programs that will improve the athlete's muscular endurance. Furthermore, programs should be designed to increase the LT velocity as a percentage of peak swimming velocity.

Assessment of linear sprinting performance: a theoretical paradigm.

The purpose of this manuscript is to describe a theoretical paradigm from which to more accurately assess linear sprinting performance. More importantly, the model describes how to interpret test results in order to pinpoint weaknesses in linear sprinting performance and design subsequent training programs. A retrospective, quasi-experimental cross sectional analysis was performed using 86 Division I female soccer and lacrosse players. Linear sprinting performance was assessed using infrared sensors at 9.14, 18.28, 27.42, and 36.58 meter distances. Cumulative (9.14, 18.28, 27.42, and 36.58 meter) and individual (1(st), 2(nd), 3(rd), and 4(th) 9.14 meter) split times were used to illustrate the theoretical paradigm. Sub-groups were identified from the sample and labelled as above average (faster), average, and below average (slower). Statistical analysis showed each sub-group was significantly different from each other (fast < average < slow). From each sub-group select individuals were identified by having a 36.58 meter time within 0.05 seconds of each other (n = 11, 13, and 7, respectively). Three phases of the sprint test were suggested to exist and called initial acceleration (0-9.14 m), middle acceleration (9.14-27.42 m), and metabolic-stiffness transition (27.42-36.58 m). A new model for assessing and interpreting linear sprinting performance was developed. Implementation of this paradigm should assist sport performance professionals identify weaknesses, minimize training errors, and maximize training adaptations. Key PointsAssessment of linear sprinting should include splits for a greater understanding of performance.Individual split times can be used to identify specific areas of weakness.Appropriate training strategies can be developed and used to improve the identified weaknesses.

Body composition in Division I football players.

This study assessed body composition of Division I football players (n = 69) and compared the findings with previously reported data to ascertain whether the increase in player total body mass that has been observed over the past 10 years has been accompanied by an increase in body fat. Body composition was determined by hydrostatic weighing and the measurement of skinfold thicknesses. Total body mass, skinfold thicknesses, and body fat were greater in the current players than in players in studies conducted in the early 1980s and early 1990s. Body fat varied significantly across playing position, with the defensive backs, offensive backs, and receivers being the leanest and the offensive linemen and tight ends the most fat. There was no significant relationship between body composition and playing year or scholarship status, nor were any differences observed between ethnic groups. Of important clinical relevance was the finding that the linemen (offensive, defensive) and tight ends were on average greater than 25% body fat, the borderline for obesity in this age group. Much of this fat was deposited in the abdominal region, a significant finding when one considers the high correlation between abdominal obesity and ischemic heart disease and stroke. The current findings suggest that more attention needs to be given to the nature of the increase in body mass being achieved by today's football player to minimize long-term negative health consequences, and the findings reemphasize the need identified in earlier studies of the importance of detraining programs for these athletes.