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The effects of a 12-over bowling spell on bowling accuracy and pace in cricket fast bowlers
Abstract
The aim of the study was to determine the effects of a 12-over fast bowling spell on bowling pace, accuracy and selected physiological variables. Subjects were randomly divided into an experimental (bowled 12 overs and performed physiological tests after each over) and a control group (only bowled the 1st and 12th over and performed physiological tests after each). The mean ball speed per over significantly decreased (p<0.05) from the 1st (32.9±2.1 ms-1 mean±SD) to the 12th over (32.1±1.8 ms-1) in the experimental group. This decrement in ball speed occurred after the 6th over. None of the physiological variables measured (heart rate, plasma lactate, lower and upper body muscle power and eye-hand reaction/eye-hand coordination) could account for the decrement in ball speed. Bowling accuracy did not significantly change from the 1st to the last over. A positive correlation (r=0.82; p<0.01) between eye-hand reaction score and bowling accuracy might explain the maintenance of accuracy during the trial. In conclusion, although bowling accuracy did not change, players and coaches should be aware of the possible decrement in ball speed after the 6th over, which could affect performance.
... [3,12] This could be due to the fact that simulated protocols do not accurately reflect the demands experienced during real match situations. [3] The only study which found a change in performance was a 12-over simulated protocol [13] . However, this is extreme and not appropriate for adolescent players nor is it typical within a cricket game generally. ...
... However, this is extreme and not appropriate for adolescent players nor is it typical within a cricket game generally. [13] While perceptions of effort and discomfort may pre-empt fatigue and injury risk, it is important to acknowledge the role of skill and mental aptitude, specifically the ability to concentrate on performance for a prolonged period of time. [14] This can also impact performance measures as shown in previous studies. ...
... [3,12] Furthermore, lower limb power was unchanged which supports previous findings. [3,13] Changes in strength are usually attributed to muscular fatigue which was not found in this study as a result of this protocol. [2,5] By contrast, this study highlighted the local perception of strain experienced by bowlers, specifically in the hamstrings. ...
Background: The demands placed on fast bowlers may elicit unique responses that contribute towards increased injury risk and comprised performance capabilities. Despite this, very few investigations have attempted to quantify these demands and their impact on performance in cricketers. Objective: This investigation attempted to quantify the effects of a fast bowling protocol on the musculoskeletal, physiological and perceptual responses of fast bowlers; as well as ball speed and accuracy. Methods: Eight young adult bowlers (20 ± 2 years) participated in a 10-over bowling protocol that had been separated by intermittent fielding drills into three bowling spells respectively (4-, 3- and 3- overs). Selected responses were collected throughout the protocol. Results: Functional strength was measured and showed no change. Heart rate responses increased significantly (p<0.05) at the start of the bowling protocol. Local ratings of perceived exertion increased significantly (p<0.05) as a function of exercise duration, while low to moderate intensities of perceived discomfort were noted in the anterior and posterior shoulder areas, upper portion of the lower limb musculature, as well as in the middle and lower back regions. Performance responses experienced no significant change. Conclusion: There was no significant change in ball release speed and accuracy across the bowling protocol. Lower limb muscle power remained consistent and heart rates reached a steady state after the first over. In comparison, local ratings of perceived effort and body discomfort increased over time, which could mean that those unchanged measures do not accurately reflect fatigue or that perceptions are a more effective indicator of impending fatigue. Keywords: accuracy, speed, heart rate, body discomfort, ratings of perceived exertion
... [3,12] This could be due to the fact that simulated protocols do not accurately reflect the demands experienced during real match situations. [3] The only study which found a change in performance was a 12-over simulated protocol [13] . However, this is extreme and not appropriate for adolescent players nor is it typical within a cricket game generally. ...
... However, this is extreme and not appropriate for adolescent players nor is it typical within a cricket game generally. [13] While perceptions of effort and discomfort may pre-empt fatigue and injury risk, it is important to acknowledge the role of skill and mental aptitude, specifically the ability to concentrate on performance for a prolonged period of time. [14] This can also impact performance measures as shown in previous studies. ...
... [3,12] Furthermore, lower limb power was unchanged which supports previous findings. [3,13] Changes in strength are usually attributed to muscular fatigue which was not found in this study as a result of this protocol. [2,5] By contrast, this study highlighted the local perception of strain experienced by bowlers, specifically in the hamstrings. ...
Background: The demands placed on fast bowlers may elicit unique responses that contribute towards increased injury risk and comprised performance capabilities. Despite this, very few investigations have attempted to quantify these demands and their impact on performance. Objectives: This investigation attempted to quantify the effects of a fast bowling protocol on the musculoskeletal, physiological and perceptual responses of fast bowlers; as well as ball speed and accuracy. Methods: Eight young adult bowlers (20 ± 1.85 years) participated in a ten over bowling protocol that had been separated by intermittent fielding drills into three bowling spells (4-,3- and3- overs). Selected responses were collected throughout. Results: Functional strength measured experienced no change. Heart rate responses increased significantly (p<0.05) in response to the start of the bowling protocol. ‘Local’ ratings of perceived exertion increased significantly (p<0.05) as a function of exercise duration while low to moderate intensities of perceived discomfort were noted in the anterior and posterior shoulder areas, upper portion of the lower limb musculature, as well as the middle and lower back regions. Performance responses experienced no significant change. Conclusion: Ball release speed and accuracy experienced no significant change across the bowling protocol, lower limb muscle power remained unchanged and heart rates reached a steady-state after the first over. In comparison, local ratings of perceived effort and body discomfort increased over time, which could mean that those unchanged measures do not accurately reflect fatigue or, that perceptions are a better indicator of impending fatigue.
... The majority of fast-bowling tests have been conducted indoors, in a lab setting that is quite possibly foreign to participants. 3,[6][7][8][9][10][11][12][13][14] Although an indoor facility may reduce the ecological validity of the assessment, it is beneficial for controlling environmental factors such as wind, rain, temperature, and humidity, especially when the effects of these variables on fast-bowling skill is not understood. In attempt to enhance the ecological validity of the assessment, 5 of the reviewed studies conducted testing outdoors. ...
... 20 Eight of the reviewed fast-bowling assessments did not report the pitch surface. 3,5,10,11,13,15,16,19 Others mentioned using a synthetic grass pitch, [6][7][8]14 a synthetic rubber pitch, 9 and a natural turf pitch. 17,18 None of the assessments reported measuring ball bounce characteristics. ...
... However, further investigation on the optimal size (mass and circumference) for juniors and females is required. Nevertheless, some of the reviewed studies have not explicitly reported the mass of the ball, 3,5,6,8,11,12,15,16,19 and most investigations have not stated the ball's circumference. 3,[5][6][7][8][9][10][11][12][15][16][17][18][19] It is important to note that simply stating the brand of the cricket ball without specifying further details can make it difficult to ascertain ball mass and circumference, as some ball names from a particular brand come in junior and senior sizes, sizes for males and females, and a variety of colors. ...
Objectives:
To evaluate the current evidence regarding the quantification of cricket fast bowling skill.
Methods:
Studies that assessed fast bowling skill (bowling speed and accuracy) were identified from searches in SPORTDiscus (EBSCO) in June 2017. The reference lists of identified papers were also examined for relevant investigations.
Results:
Sixteen papers matched the inclusion criteria, and discrepancies in assessment procedures were evident. Differences in: test environment, pitch and cricket ball characteristics, the warm-up prior to test, test familiarisation procedures, permitted run-up lengths, bowling spell length, delivery sequence, test instructions, collection of bowling speed data, collection and reportage of bowling accuracy data were apparent throughout the literature. The reliability and sensitivity of fast bowling skill measures has rarely been reported across the literature. Only one study has attempted to assess the construct validity of their skill measures.
Conclusions:
There are several discrepancies in how fast bowling skill has been assessed and subsequently quantified in the literature to date. This is a problem, as comparisons between studies are often difficult. Therefore, a strong rationale exists for the creation of match-specific standardised fast bowling assessments that offer greater ecological validity while maintaining acceptable reliability and sensitivity of the skill measures. If prospective research can act on the proposed recommendations from this review, then coaches will be able to make more informed decisions surrounding player selection, talent identification, return to skill following injury, and the efficacy of short- and long-term training interventions for fast bowlers.
... One study found heart rates of between 154 and 158 bt.min -1 during a 6-over fast bowling spell (Devlin et al., 2000). This was confirmed by Taliep et al. (2003) who found that heart rates during fast bowling ranged between 73% and 77% HR max. Burnett et al. (1995) reported peak heart rates of between 180 and 190 bt.min -1 during a 12-over fast bowling spell. ...
... During a 6 to 8-over spell, bowling speed remains unchanged while accuracy has shown some non-significant variation (Portus et al., 2000;Devlin et al., 2000). In contrast, Taliep et al. (2003) found significant reductions in bowling speed after the 6 th over in a 12-over bowling spell and no change in accuracy. Noakes & Durandt (2000) speculate that the main cause of stress for cricket players is the repeated eccentric muscle damage resulting from multiple declarations that occur in batting and fast bowling. ...
... There are many factors comprising cricket pace bowling performance during match play, such as wickets taken, strike rate (runs conceded per wicket), and economy (average runs scored per over). An elite pace bowler should have the necessary skill to bowl quickly, accurately, and consistently fast and accurately (44) during a bowling spell (series of overs; an over is equivalent to 6 legal deliveries) or repeated bowling spells throughout a match. A faster delivery speed simply reduces a batter's reaction time and movement time (48), which may result in a greater likelihood of the batter not striking the ball or mistiming the ball strike. ...
Feros, SA, Young, WB, and O'Brien, BJ. Efficacy of combined general, special, and specific resistance training on pace bowling skill in club-standard cricketers. J Strength Cond Res XX(X): 000-000, 2018-This study investigated the efficacy of combined "general," "special," and "specific" resistance training on pace bowling skill. Twelve male, club-standard pace bowlers were randomly allocated to a combined resistance training (CRT) program or traditional cricket training (TCT) program for 8 weeks. The CRT group (n = 6) trained with 300, 250-g, and standard cricket balls; performed 20-m sprints with +20% and +15% body mass resistance (but also unresisted); and completed chin-up and pull-up training. The TCT group (n = 6) trained with standard balls and performed unresisted 20-m sprints. No statistically significant GROUP × TIME interactions were identified. The CRT group demonstrated a "clear moderate" enhancement in peak ball release speed (mean ±95% confidence limits [CLs]: 1.2 ± 1.5 m·s, d = 0.66 ± 0.83), a "clear large" increase in mean radial error (mean ±95% CLs: 7.1 ± 6.5 cm, d = 0.94 ± 0.87), and a "clear large" rise in bivariate variable error (mean ±95% CLs: 7.2 ± 7.8 cm, d = 0.97 ± 1.05). The TCT group exhibited "unclear" changes across all pace bowling skill measures. Both groups displayed "unclear" changes in approach speed, 20-m sprint time, and 1 repetition maximum pull-up strength. In 8 weeks, the CRT program improved peak ball release speed, but at the cost of poorer bowling accuracy and consistency of bowling accuracy. These findings could be attributed to bowling with the heavier balls. The inclusion of "specific" resistance training does not seem to be effective in enhancing all-round pace bowling skill in club-standard cricketers.
... A factor not included in this study was ball velocity. There is evidence to suggest that fast bowlers decrease their speed to maintain accuracy (Taliep et al., 2003). Therefore, measuring ball velocity would have provided further insight into aspects of bowling performance following fatiguing exercise and taping interventions. ...
The impact that muscle fatigue and taping have on proprioception in an applied sporting context remains unclear. The purpose of this study was to investigate disturbances in position sense at the shoulder joint, and asses the effectiveness of adhesive tape in preventing injury and improving performance, after a bout of cricket fast bowling. Among amateur cricket players (N = 14), shoulder position sense, maximum voluntary contraction (MVC) force and bowling accuracy was assessed before and immediately after a fatiguing exercise bout of fast bowling. Participants were tested with the shoulder taped and untapped. Shoulder extension MVC force dropped immediately and 30 min after the exercise (P < 0.05 and P < 0.05, respectively). Position sense errors increased immediately after exercise (P < 0.05), shifting in the direction of shoulder extension for all measurements. Taping had no effect on position errors before exercise, but did significantly reduce position errors after exercise at mid-range shoulder flexion angles (45° and 60°; P < 0.05 and P < 0.05, respectively). Taping had no significant effect on bowling accuracy. These findings may be explained by a body map shift towards a gravity neutral position. Added cutaneous input from the tape is proposed to contribute more to shoulder position sense when muscles are fatigued.
... Bowling performance has been shown to decrease after a long bowling spell. 16 It is therefore possible that black African bowlers are more fatigue resistant, allowing them to sustain high performances over extended periods. This could be a reason why the majority of black African bowlers are specialist bowlers. ...
Abstract
Objectives. This study investigates the effectiveness of the cricket
transformation process in firstly increasing representation of
black players and secondly improving performance of black players
in the South African 4-day provincial competition between the
1996/1997 and 2007/2008 cricket seasons.
Methods. Cricketers were categorised as white, black African
or coloured/Indian. Whenever the category ‘black’ is mentioned
alone, it refers to black African and coloured/Indian. All data were
obtained from www.cricinfo.com.
Results. The number of white players decreased and the number
of black African and coloured/Indian players increased between
the 1996/1997 and 2007/2008 seasons. White batsmen had significantly
higher batting averages than black Africans, but were
only better than coloureds/Indians in the 2001/2002 season. Coloureds/
Indians had better batting averages than black Africans
in all seasons except 2001/2002 and 2004/2005. There was a
significant improvement in the batting averages of coloureds/Indians
but not of whites and black Africans over the 12 seasons.
White bowlers had significantly better bowling averages than
coloured/Indian bowlers for seasons 2002/2003, 2004/2005 and
2006/2007. There were no significant differences in the bowling
averages between white and black African players and between
coloured/Indian and black African players over the 12 seasons.
There was a tendency towards a decreased bowling performance
for coloureds/Indians, whereas there was no significant decrement
in the bowling performance for whites and black Africans
over the 12 seasons.
Conclusion. The increase in the number of black cricketers performing
according to standard suggests a reasonable successful
transformation process. However, representation and batting performance
of black African batsmen remain a concern.
... Devlin and colleagues [48] reported that moderate exercise-induced hypohydration impaired bowling accuracy but not ball release speed in sub-elite standard fast–medium cricket bowlers. Taliep and colleagues [49] found that there was no change in bowling accuracy over the course of a 12-over bowling spell but there was a decrease in ball release speed, particularly after the sixth over. Petersen and colleagues [50] showed that training with overweight and underweight cricket balls over a 10-week period decreased bowling accuracy but only slightly increased ball release speed. ...
To date, scientific investigations into the biomechanical aspects of cricket fast bowling techniques have predominantly focused on identifying the mechanical factors that may predispose fast bowlers to lower back injury with a relative paucity of research being conducted on the technical features that underpin proficient fast bowling performance. In this review paper, we critique the scientific literature examining fast bowling performance. We argue that, although many published investigations have provided some useful insights into the biomechanical factors that contribute to a high ball release speed and, to a lesser extent, bowling accuracy, this research has not made a substantive contribution to knowledge enhancement and has only had a very minor influence on coaching practice. To significantly enhance understanding of cricket fast bowling techniques and, therefore, have greater impact on practice, we recommend that future scientific research adopts an interdisciplinary focus, integrating biomechanical measurements with the analytical tools and concepts of dynamical systems motor control theory. The use of qualitative (topological) analysis techniques, in particular, promises to increase understanding of the coordinative movement patterns that define ‘technique’ in cricket fast bowling and potentially help distinguish between functional and dysfunctional aspects of technique for individual fast bowlers.
The manifestations of fatigue during fast bowling in cricket were systematically evaluated using subjective/perceptual reports by cricket experts and quantitative data published from scientific studies. Narratives by international players/team physiotherapists were sourced from the internet using criteria for opinion-based evidence. Research articles were evaluated for high-level fast bowlers who delivered 5-12 over spells with at least one quantitative fatigue measure. Anecdotes indicate that a long-term loss of bowling speed, tiredness, mental fatigue and soreness occur. Scientific research shows that ball release speed, bowling accuracy, bowling action (technique), run-up speed, and leg muscle power are generally well maintained during bowling simulations. However, bowlers displaying excessive shoulder counter rotation towards the end of a spell, also show a fall in accuracy. A single notable study involving bowling on two successive days in the heat, showed a reduced ball release speed (-4.4km/h), run-up speed (-1.3km/h) and accuracy. Moderate-to-high ratings of perceived exertion transpire with simulations and match-play (6.5-7.5 Borg CR-10 scale). Changes of blood lactate, pH, glucose, and core temperature appear insufficient to impair muscle function, although several potential physiological fatigue factors have not been investigated. The limited empirical evidence for bowling-induced fatigue appears to oppose the player viewpoints and indicates a paradox. However this may not be the case since: i) bowling simulations resemble the shorter formats of the game but not multi-day (Test-match) cricket, nor the influence of an arduous season, and ii) comments of tiredness, mental fatigue and soreness, signify different phenomena to what scientists measure as fatigue.
Twenty-four male fast bowlers of mean age 13.7 years, who bowled competitively at a school and club level were selected from five Western Australian schools. At the time of the testing all bowlers, who were bowling completely freely, underwent magnetic resonance imaging to detect the presence of intervertebral disc abnormalities. While these radiological data were being analysed, the players were filmed both laterally (200 Hz) and from directly above (100 Hz) as their front foot impacted a force platform during the delivery stride of the fast bowling action. In addition these bowlers performed selected physical capacity tests. The occurrence of abnormal radiological data were then used to group the bowlers (group 1, no abnormal features; group 2, disc degeneration and/or bulging on scan). A Mann-Whitney U rank test was then used to identify any significant differences (P < 0.1) between the groups for all dependent variables. Five of the subjects recorded abnormal magnetic resonance imaging scans of the lumbar spine, while nineteen recorded normal intervertebral discs, normal alignment of the lumbar spine, and no sign of spondylolisthesis. Bowlers who rotated the trunk to realign the shoulders to a more side-on position between back foot impact and front foot impact in the delivery stride were more likely to record abnormal intervertebral disc features.
A maximal multistage 20 m shuttle run test was designed to determine the maximal aerobic power of schoolchildren, healthy adults attending fitness class and athletes performing in sports with frequent stops and starts (e.g. basketball, fencing and so on). Subjects run back and forth on a 20 m course and must touch the 20 m line; at the same time a sound signal is emitted from a prerecorded tape. Frequency of the sound signals is increased 0.5 km h-1 each minute from a starting speed of 8.5 km h-1. When the subject can no longer follow the pace, the last stage number announced is used to predict maximal oxygen uptake (VO2max) (Y, ml kg-1 min-1) from the speed (X, km h-1) corresponding to that stage (speed = 8 + 0.5 stage no.) and age (A, year): Y = 31.025 + 3.238 X - 3.248A + 0.1536AX, r = 0.71 with 188 boys and girls aged 8-19 years. To obtain this regression, the test was performed individually. Right upon termination VO2 was measured with four 20 s samples and VO2max was estimated by retroextrapolating the O2 recovery curve at time zero of recovery. For adults, similar measurements indicated that the same equation could be used keeping age constant at 18 (r = 0.90, n = 77 men and women 18-50 years old). Test-retest reliability coefficients were 0.89 for children (139 boys and girls 6-16 years old) and 0.95 for adults (81 men and women, 20-45 years old).(ABSTRACT TRUNCATED AT 250 WORDS)
In order to validate a maximal multistage 20-m shuttle run test for the prediction of VO2 max, 91 adults (32 females and 59 males, aged 27.3 +/- 9.2 and 24.8 +/- 5.5 year respectively and with mean VO2 max (+/- SD) of 39.3 +/- 8.3 and 51.6 +/- 7.8 ml . kg-1 . min-1 respectively) performed the test and had VO2 max estimated by the retroextrapolation method (extrapolation to time zero of recovery of the exponential least squares regression of the first four 20-s recovery VO2 values). Starting at 8 km . h-1 and increasing by 0.5 km . h-1 every 2 min, the 20-m shuttle run test enabled prediction of the VO2 max (y, ml . kg-1 . min-1) from the maximal speed (x, km . h-1) by means of the following regression equation: y = 5.857x - 19.458; r = 0.84 and SEE = 5.4. Later, the multistage protocol was slightly modified to its final version, in which the test started at stage 7 Met and continued with a 1 Met (3.5 ml O2 . kg-1 . min-1) increment every 2 min. Twenty-five of the 91 subjects performed the 20-m shuttle test twice, once on a hard, low-friction surface (vinyl-asbestos tiles) and another time on a rubber floor, as well as a walking maximal multistage test on an inclined treadmill. There was no difference between the means of these tests or between the slopes of the VO2max - maximal speed regressions for the two types of surfaces. The 20-m shuttle run test and another maximal multistage field test involving continuous track running gave comparable results (r = 0.92, SEE = 2.6 ml O2 . kg-1 . min-1, n = 70). Finally, test and retest of the 20-m shuttle run test also yielded comparable results (r = 0.975, SEE = 2.0 ml O2 . kg-1 . min-1, n = 50). It is concluded that the 20-m shuttle run test is valid and reliable test for the prediction of the VO2 max of male and female adults, individually or in groups, on most gymnasium surfaces.
Nine members of the Western Australian Cricket Association fast bowling development squad were selected to determine the effects that a 12-over spell would have on fast bowling technique and selected physiological variables. Three high-speed cameras operating at 100 Hz filmed the subjects bowling the 5th and 6th balls of their 1st, 6th, 10th and 12th overs. Blood lactate and heart rate were recorded and the bowlers were shown to work at between 80.3% (1st over) to 84.7% (12th over) of their maximum heart rate during the 12-over bowling spell. Data from the 5th and 6th deliveries from each over were averaged to provide representative data, as no significant differences were evident between these two deliveries for the selected kinematic variables. For all subjects, no significant differences were recorded for the selected kinematic variables throughout the duration of the 12-over spell, indicating that in general fast bowling technique does not change over this length of spell. In addition, there was some evidence of change in technique for the bowlers who used a front-on action, where counter-rotation of the shoulders was found to increase; however, this could only be confirmed by a more comprehensive study.
Objective: Sedative hypnotics are used by athletes to alleviate precompetition anxiety and insomnia. The effects of these agents on exercise tolerance have not been extensively researched.
Design: To determine the effects of sedative hypnotics on psychomotor and physical performance, a double-blind, placebo- (P) controlled, cross-over designed trial investigated the effects of zopiclone (Z) and loprazolam (L) on performance in 12 athletes.
Intervention: Subjects ingested either P, Z (7.5 mg), or L (2 mg) on three different occasions separated by a 1-week washout period. Eye-hand coordination tests, a 30-m sprint test, an agility test, and a graded treadmill run to exhaustion for determination of VO2max were performed 10 hours after drug administration.
Results: Subjects reported a significantly greater hangover effect following ingestion of L (8/11 subjects) compared with ingestion of Z (3/11 subjects; p < 0.01). A greater number of subjects felt alert after ingestion of P (9/11 subjects) and Z (9/11 subjects) compared with L (4/11 subjects; p < 0.01). The results of the eye-hand coordination tests, the 30-m sprint, the T-test, the VO2max, and the time to exhaustion during the treadmill run were not significantly altered following the ingestion of P, Z, and L. There was a significant difference between the delta values for Z and L for the number of missed responses in the eye-hand coordination tests (p < 0.02). Therefore, following the ingestion of L, subjects experienced a significant hangover effect and altered reaction time, whereas the ingestion of Z did not significantly impair either psychomotor or physical performance in the administered tests.
Clinical Relevance: Investigate the extent of the effects of sedative hypnotics on exercise performances, enabling team physicians to prescribe such drugs to the athlete more effectively.
Force-velocity and power-velocity curves in a vertical jump involving movements around several joints were derived from vertical ground reaction forces and knee angular velocities. The jumps were performed with weights from 10 to 160 kg added on the shoulders. The obtained curves from a semi-squatting static starting position resembled those reported for isolated muscles or single muscle groups. Vertical jumps were also performed in the conditions where the shortening of the leg extensors was preceded by prestretching of the active muscles either through a preparatory counter-movement or dropping down on the force-platform from the various heights ranging from 20 to 100 cm. Prestretching modified through a range of velocities the force-velocity and power-velocity curves by increasing both the ground reaction forces and the calculated mechanical power. Thus the results are similar to those reported in isolated muscles. In studies with isolated muscle preparation the nervous connections have not been intact and therefore it is suggested that increase in the performance of the skeletal muscles through prestretching, in the conditions of the present study, was attributed to the combined effects of the utilization of stored elastic energy and the reflex potentiation of muscle activation.
1. Skinfold thicknesses at four sites – biceps, triceps, subscapular and supra-iliac – and total body density (by underwater weighing) were measured on 209 males and 272 females aged from 16 to 72 years. The fat content varied from 5 to 50% of body-weight in the men and from 10 to 61% in the women.2. When the results were plotted it was found necessary to use the logarithm of skinfold measurements in order to achieve a linear relationship with body density.3. Linear regression equations were calculated for the estimation of body density, and hence body fat, using single skinfolds and all possible sums of two or more skinfolds. Separate equations for the different age-groupings are given. A table is derived where percentage body fat can be read off corresponding to differing values for the total of the four standard skinfolds. This table is subdivided for sex and for age.4. The possible reasons for the altered position of the regression lines with sex and age, and the validation of the use of body density measurements, are discussed.
An initially submaximal hopping task was maintained with the same global power output until it became the maximal performance; since there was no decrease in performance, any change in behavior occurring with fatigue characterizes the strategies allowing to compensate for the effects of fatigue. In a prolonged hopping task, fatigue is likely to be most prominent in the ankle extensor muscles since they are the main contributors to vertical propulsion in the hop. With fatigue, all subjects landed with more flexed knees and with an increased activity in the biarticular rectus femoris muscle indicating some compensation between the knee and ankle joint. Furthermore, two different strategies appeared to further compensate for the important fatigue of the ankle extensor muscles: one was organized across joints and consisted in a heavier reliance of the knee extensor vastus lateralis, and the other was organized within the fatigued joint and consisted in an earlier preactivation of the gastrocnemius. As a consequence, two different adaptations of the ground reaction force profiles appeared at the end of the session; each being related to one of these two strategies.
The purpose of this research was to perform isometric tests at two joint angles and examine their relationship to dynamic performance. In addition, electromyograph data were collected from the triceps brachii and pectoralis major muscles to compare underlying neural characteristics between the isometric tests and dynamic movement. A group of 24 healthy male subjects performed two isometric tests in a bench press position, at elbow angles of 90 and 120 degrees. From these data, the maximal force and rate of force development were determined. In addition, each subject performed a seated medicine ball throw as a measure of dynamic upper body performance. Correlations showed that isometric measurements of force (r = 0.47-0.55) and rate of force development (r = 0.08-0.31) were poor predictors of dynamic performance. The angle of isometric assessment had little effect on the relationship between the tests and measurements of performance. The myo-electric data was processed in terms of the integrated electromyogram and the Fourier transformed frequency spectrum. These data demonstrated differences in the neural activation patterns of the musculature, between the isometric 90 degrees test and the medicine ball throw. The poor relationship between isometric tests and medicine ball performance was consequently, at least partially, attributed to differing motor unit activation patterns between isometric and dynamic movement. The results of this research strongly suggest that isometric tests have limited value when assessing dynamic upper body performance.