Syfte och frågeställningar Syftet med studien var att undersöka hur stretching i olika former akut påverkar hopphöjd. Vilken akut påverkan har statisk stretching på hopphöjd? Vilken akut påverkan har dynamisk stretching på hopphöjd? Vilka skillnader i hopprestation finns när det gäller den akuta effekten efter statisk och dynamisk stretching? Metod Studien var kvantitativ med en experimentell forskningsdesign och bestod av tre testtillfällen. Bekvämlighetsurval tillämpades och begränsades till 12 friska fysiskt aktiva kvinnor i åldrarna 18-30 år. Varje testtillfälle innehöll en uppvärmning på ergometercykel, tre vertikalhopp, en stretchingintervention (statisk, dynamisk eller kontroll), en aktiv vila på ergometercykel och ytterligare tre vertikalhopp. Vertikalhoppen (squat jump) utfördes på en kontaktmatta som beräknade den totala hopphöjden. De muskelgrupper som stretchades var gluteus maximus, hamstrings, quadriceps femoris och triceps sure. Tiden för den statiska stretchingen var 4 x 30 sekunder (s.) per muskelgrupp. Den dynamiska stretchingen utfördes med gungande rörelser i 1:1 s. cykler under 30 s. Under kontrolltillfället bedrevs ingen stretching alls. Resultat Testpersonernas medelvärde var 22,7  i ålder och 23,9 i BMI. Medelhöjden på hoppen efter den statiska stretchingen minskade signifikant med 5,4 % (p =0,009). Efter den dynamiska stretchingen sågs ingen skillnad i hopphöjd. Ingen skillnad sågs heller i jämförelsen mellan den statiska och den dynamiska stretchingen. Slutsats Resultaten visade att statisk stretching med en total tid på två minuter inte bör utföras innan en maximal hopprestation. Att stretcha dynamiskt hade ingen påverkan på hopprestationen.

The primary purpose of this thesis was to understand the relationship between the variation in athlete segment lengths (trunk, thigh, shank) and front squat depth as represented by maximum thigh segment rotation angle within the recommended guidelines. A validated segmental anthropometric model was used to simulate the effects of progressively altering thigh and trunk lengths on front squat depth. Both the thigh and trunk lengths were independently progressed through +/- 3 standard deviations, using the anthropometry collected from 41 athletes. This was done for simulated subjects of short (1.65 m for male and 1.55 m for females), average (1.82 m for male and 1.70 m for female), and tall (2.01 m for male and 1.87 m for females) statures. As thigh length increased, the ability to perform a full front squat (to a thigh depth of 180 degrees relative to the right horizontal) decreased. Conversely, as trunk length decreased, the ability to perform a full front squat decreased. The model was modified to progressively alter the thigh-to-trunk ratio from 0.8 to 1.2 for individuals of short, average and tall statures. Effects were similar for all heights for both males and females. Individuals with a thigh-to-trunk ratio above 1 were simulated to not be able to achieve a full front squat. This effect was greater in tall individuals, followed by average and then short. The ankle flexibility measured from the 41 athletes was run in simulations to determine its effects on front squat depth. For 25 of the athletes, the ankle flexibility did not allow their knees to pass the vertical plane of the toes. Flexibility constraints were removed from the model and the knees were moved to the vertical plane of the toes, 5 cm past, and 10 cm past. When the knees were allowed to move to the vertical projection of the toes, 8 athletes could not achieve a full front squat. When the knees were allowed to move 5 cm past the vertical projection of the toes, all athletes were predicted to be able to achieve a full front squat. When ankle flexibility was factored into the model, the results predicted that 16 athletes could not achieve a full front squat. The effects of ankle flexibility on front squat depth appeared to be influenced by the thigh-to-trunk ratio. Of the eight participants predicted not to be able to achieve a full front squat when the knees were allowed to reach the vertical projection of the toes, five had the largest thigh-to-trunk ratios. Athletes with a thigh-to-trunk ratio of 1 or greater may physically not be able to complete a full front squat according to the NSCA guidelines. It is however, more likely that the thigh-to-trunk ratio, which may limit the ability to achieve a full front squat, is significantly less than 1 when a trunk angle greater than 60 degrees is used. Furthermore, anterior knee translation initiated through rotation of the shank appears to be a strategy to maintain equilibrium at the end ranges of the front squat movement. It appears plausible that horizontal knee motion up to 5 cm past the vertical projection of the toes may allow athletes with large thigh-to-trunk ratios to reach full front squat depth and perhaps reduce loading on the low back. Additionally, ankle inflexibility may limit front squat depth.

To examine differences in body composition and maximal strength between collegiate (CLG) and men's club (CLB) rugby union players, as well as between the forward (FW) and back (BK) positions, seventeen resistance-trained men (24 ± 2.4 yrs; range: 20 ± 27 yrs; 179.3 ± 5.4 cm; 93.7 ± 12.9kg) from a collegiate rugby team (n=11) and a local men's rugby club (n=6) were recruited to participate in the present investigation. Prior to strength testing, height (± 0.1 cm), body mass (± 0.1 kg), and body composition via dual energy x-ray absorptiometry were assessed to determine total percent body fat (%FAT), lean body mass (LBM), lean arm mass (LAM), and lean leg mass (LLM). Maximal upper- and lower-body strength were determined from each participant's one-repetition maximum (1RM) in the bench press and squat, respectively. Additionally, athletic history, resistance training experience, and distractors (e.g. work, school, and sleep) were determined via questionnaire. Significant (p<0.05) differences were observed between clubs in age (CLG: 22.3 ± 1.3y; CLB: 26.2 ± 1.1y), years played (CLG: 2.9 ± 2.4y; CLB: 7.5 ± 2.1y), and starting experience (CLG: 1.7 ± 2.6y; CLB: 5.2 ± 3.4y). In terms of position, LAM was significantly (p = 0.037) greater in FW (10.6 ± 1.7kg) than in BK (9.0 ± 0.5kg). These findings suggest rugby union players possess similar strength and size characteristics, regardless of age, playing experience, or position.

No description available.

Abstract available in the Annual Coaches and Sport Science College.

The purpose of this study was to examine the relationships between muscle cross-sectional area (CSA), maximal strength, power output, and maximum potentiation characteristics. The vastus lateralis and biceps femoris CSA, one repetition maximum (1RM) back squat, 1RM concentric-only half-squat (COHS) strength, static jump power output, and maximum potentiation characteristics of 17 resistance-trained men was assessed during several testing sessions. Pearson’s correlation coefficients were used to examine the relationships between CSA, strength, power output, and maximum potentiation measures. Moderate-to-strong relationships existed between CSA and strength measures (r = 0.462–0.643) as well as power output (r = 0.396–0.683). In addition, moderate-to-strong relationships existed between strength and power output (r = 0.407–0.548), while trivial relationships existed between strength and maximum potentiation (r = −0.013–0.149). Finally, small negative relationships existed between CSA and maximum potentiation measures (r = −0.229–−0.239). The results of the current study provide evidence of the interplay between muscle CSA, strength, power, and potentiation. Vastus lateralis and biceps femoris CSA may positively influence an individual’s back squat and COHS maximal strength and squat jump peak power; however, muscle CSA and absolute strength measures may not contribute to an individual’s potentiation capacity. Practitioners may consider implementing resistance training strategies that improve vastus lateralis and biceps femoris size in order to benefit back squat and COHS strength. Furthermore, implementing squatting variations—both full and partial—may benefit jumping performance.

Abstract Post-activation potentiation (PAP) is a phenomenon where force output is acutely enhanced following muscular contraction. Previous research has documented enhanced performance in power-type light exercise following a heavy pre-load, such as vertical jumps following heavy squats. To date, the effect of PAP on moderately heavy exercise following a heavy pre-load has not been investigated. Purpose: The purpose was to examine whether PAP could be elicited in moderately heavy squats following a heavy squat pre-load, and if so, what intensity (as percentage of one repetition-maximum [1RM]) of pre-load elicited the highest PAP effect (measured as mean power, mean force and number of repetitions performed). Subjects: Seventeen resistance-trained males (age 24±2 years, length 182±8 cm, body mass 84.7±13.1 kg, squat 1RM 147.6±29.6 kg) with at least 2 years of experience of the squat exercise. Methods: After testing parallel squat 1RM at a separate session, subjects performed three testing sessions in a randomized order in a cross-over design; performance test at 80% of parallel squat 1RM (control), one repetition at 85% of 1RM followed 8 minutes later by the same performance test (PAP85), and one repetition at 93% of 1RM followed 8 minutes later by the same performance test (PAP93). Sessions were separated by six days. Force and power output was recorded using a linear encoder. Friedman’s test was used to reveal differences between conditions, and a Wilcoxon signed rank test was used to identify these differences. Results: There was an increase in number of repetitions performed for PAP85 (p=0.009) and PAP93 (p=0.001) compared to control, but not for mean power or mean force. There was no significant difference between PAP85 and PAP93 for number of repetitions (p=0.091). Conclusion: PAP can be elicited to improve performance in moderately heavy squats following a heavy squat pre-load in trained subjects, but only measured as number of repetitions performed, not force or power. PAP could therefore be useful not only for designing power training, but also for strength and hypertrophy training. KEYWORDS: squat, post-activation potentiation, PAP, strength, power, hypertrophy.

Background: Post activation potentiation (PAP) is an increased muscular performance thatoccurs after maximal voluntary contraction. Previous studies have shown a significantincrease in explosive movements, such as sprint and jump performance, as an effect ofthese maximal contractions. Aim: The aim of this study was to analyze if PAP, in terms of heavy squats, has aperformance enhancing effect on 30 meter sprint, with a hypothesis that the maximal effortin the squat has a performance enhancing effect on 30 meter sprint. Method: Twelve healthy male Crossfit athletes from Crossfit Halmstad, age between x-x,volunteered to participate in the study, eleven of these completed all of the test sessions in thiscross-sectional study. During the first test session, the subjects attempted to set a onerepetition max (1RM) in the back squat. During the second and third test session, the subjectswere randomly divided into two groups and the subjects got to perform both the non-PAP andthe PAP protocol during different sessions, depending on which group they were in. Thesprint time was measured with a handheld stopwatch. Wilcoxon Signed Rank Test was usedto determine significant differences between sprint time after the two different protocols, andthe level of significance was set at p &lt; 0.05. Result: The result showed that there was no significant difference between PAP and non-PAPprotocols (p = 0,679). With a median value of 4,78 seconds, a minimum value of 4,59seconds and a maximum value of 5,54 seconds for the sprint trials after PAP and a medianvalue of 4,82 seconds, a minimum value of 4,59 seconds and a maximum value of 5,31seconds for the sprint trials without PAP, the results did not confirm the hypothesis. Conclusion: As an effect from the low number of participants, the result could be deceptive.The study could have show a different result if the number of participants would exceed atleast 25 subjects. There are no performance enhancing effects in the sprint after PAP, in thisstudy. Further research is required, to determine possible performance enhancing effectsfrom PAP.

ABSTRACT  Title of dissertation: Analysis and comparasion of squat exercise due to surface EMG  Objectives of dissertation: To measure and describe the structure involving specific muscles durring back squat, front squat and smith machine squat exercise.  Method: Surface EMG analysis and simple kinematic analysis.  Results: Activation of m. gluteus maximus was highest after the start of excentric movement. Main muscle working on the chase between the concentric and excentric movement was m. rectus femoris. Very similar timing and synergy were between m. erector spinae and m. biceps femoris. In this study was not higher activation of m. quadriceps femoris during front squat exercise, activation of m. gluteus maximus were also higher.  Key words: squat, strengthening, bar, front squat, back squat, Smith machine squat, bodybuilding, weightlifting, powerlifting, EMG analysis, kinematic analysis 6

No study has examined the effect of exercise modality (free weight vs. machine weight) on the acute hormonal response using similar multi-joint exercises. The purpose of this investigation was to examine the effect of resistance exercise modality on acute hormonal responses by comparing the squat and leg press which are multi-joint, and similar in action and lower-body muscle involvement. Ten resistance trained men (21-31 y, 24.7 ± 2.9 y, 179 ± 7 cm, 84.2 ± 10.5 kg) participated in the study. Sessions 1 and 2 determined the participants’ 1-RM in the squat and leg press. During acute heavy resistance exercise testing visits (AHRET), sessions 3 and 4, participants completed 6 sets of 10 repetitions with an initial intensity of 80% of their 1-RM for the squat and leg press exercises. There was a 2 minute rest period between each set. Blood samples were collected before, immediately after, and 15 and 30 minutes after exercise via intravenous catheter during the AHRET visits and were analyzed for testosterone, cortisol, and growth hormone. Lactate, plasma volume change, heart rates and ratings of perceived exertion were also measured. Total work was calculated for external load only and for external load and the body mass used in the exercises. The 4 sessions were counterbalanced and randomized for exercise mode. Testosterone for the squat (Pre: 23.9 ± 8.7 nmol•L-1; IP: 31.4 ± 10.3 nmol•L) and leg press (Pre: 22.1 ± 9.4 nmol•L-1; IP: 26.9 ± 7.8 nmol•L) increased but more significantly after the squat. Growth hormone increased in both the squat (Pre: 0.2 ± 0.2 µg/L; IP: 9.5 ± 7.3 µg/L) and the leg press (Pre: 0.3 ± 0.5 µg/L; IP: 2.8 ± 3.2 µg/L). The increase was significantly higher after the squat compared to the leg press. Cortisol also increased after performing the squat (Pre: 471.9 ± 167.2 nmol•L-1; IP: 603.2 ± 277.6 nmol•L) and leg press (Pre: 463.5 ± 212.4 nmol•L-1; IP: 520.3 ± 270.3 nmol•L), but there was no significant difference between the two modes. The total work was significantly higher in the squat (60509 ± 10759 j) compared to the leg press (42875 ± 7010). The squat exercise is more effective at inducing an acute hormonal response. If the leg press exercise is used, the hormonal response may be reduced, which might lead to reduced training adaptations, especially when only a 90º knee angle ROM is used. To induce the maximal hormonal response to resistance exercise, free weight exercises should be used.