Resistance training is widely prescribed for rehabilitation of injuries and as a method to improve athletic performance. It is accepted that resistance training increases the maximal force production of whole muscle and it has been suggested that the velocity of shortening can increase as well. However, little is known about the effects of resistance training at the cellular level. Therefore, we investigated morphology, force production, velocity, and force-velocity-power relationships of single chemically skinned muscle fibers from chronically resistance trained humans, including cross sectional area (CSA), peak Ca²⁺ -activated force production (P₀), specific tension (P₀/CSA), unloaded shortening velocity (V₀), and isotonic contractions. The untrained group (NT) group consisted of sedentary males (n=6, age =27 ± 2 yrs) while the chronically trained group (CHRT) group consisted of males with 7.7 ± 0.4 yrs resistance training experience (n=6, 22 ± 1 yrs). Maximum voluntary isometric and isokinetic knee extensor strength were measured along with 6 repetition maximum (6RM) free weight bench press and leg press. Muscle biopsies were obtained from the vastus lateralis. Chemically skinned single muscle fibers were mounted between a force transducer and servo-controlled motor and subjected to slack tests to determine peak Ca²⁺ -activated force (P₀) and unloaded shortening velocity (V₀). Isotonic load clamps were used to determine the force-velocity-power relationship. All fiber experiments were performed at 15°C. Fiber myosin heavy chain (MHC) content was determined by gel electrophoresis. The CHRT group was 119% and 81% stronger for 6RM leg press and bench press respectively. Peak isometric torque was 28% greater for the CHRT subjects and was significantly higher at all isokinetic speeds tested. No differences were seen in strength or isokinetic power between groups after normalization for lean body mass. CHRT fibers (n=213) expressing type I, IIa, and I₀a/IIx MHC were significantly greater in CSA (+41%, +51%, and +33%, respectively) and produced significantly greater P₀ (+37%, +48%, and +34%, respectively) than NT fibers (n=236). However, P₀/CSA was not different between CHRT and NT groups. Fibers expressing type IIa/IIx fibers produced greater P₀/CSA than IIa which produced greater P₀/CSA than type I. The P₀/CSA relationship between fibers within groups was type IIa/IIx>IIa>I and was significant for both groups. Fiber V₀ was not different between groups. Absolute power was significantly greater in the CHRT for all fiber types whereas power normalized for fiber volume was not different between groups. This resulted in a significantly greater force at peak power for all but type IIa/IIx fibers and trends for greater velocity at peak power. Single-cell contractile function in terms of V₀ and P₀/CSA, measured under standardized conditions, appears to be unaltered as a result of long term CHRT in young adult males. Group differences in absolute P₀ can be attributed solely to the greater CSA of the CHRT fibers. Long-term CHRT is not associated with a difference in fiber V₀. Therefore, the greater power was due entirely to the greater force. These data suggest that differences in whole muscle strength and power between NT and CHRT groups are primarily due to differences in fiber CSA rather than differences in cross-bridge mechanisms of contraction. Supported by National Institute of Health grant R3AR46392A. / Graduation date: 2002

Fourteen college softball players were recruited to participate in this study to determine if a strength imbalance between the lower extremities, how significant this difference this may be and of any correlations existed among all the functional tests. Subjects took part in isokinetic flexion and extension at 60 and 240 deg/sec, parallel squats, 2-legged vertical jump, single leg vertical jump, and a five-hop test. Peak and average torque was recorded for isokinetic testing and revealed significant differences between the dominant and non-dominant limbs (13.00%- 16.00%). Peak and average force was analyzed for squats and all vertical jumps. Significance was found among all activities between dominant and non-dominant legs, other than average force for single leg vertical jump. A significant difference was also exhibited for the five-hop test between the lower extremities. Significant correlations were also found at the 0.05 and 0.01 levels amongst the various functional tests. Overall findings revealed a significant strength imbalance between the dominant and non-dominant limbs. Further research needs to be conducted in determining how detrimental these differences could be in daily performance for athletes. / School of Physical Education

Thesis (MScMedSc (Biomedical Sciences))--University of Stellenbosch, 2005. / The purpose of this study was to determine the physiological and kinanthropometric attributes, respiratory muscle strength, and core stability of successful endurance paddlers, and to investigate the associations of these characteristics with kayak endurance performance in the laboratory and the field. Twenty male competitive paddlers (age: 28 ± SD 7 years, height: 184 ± SD 7 cm and weight: 80 ± SD 7 kg) were categorised in two ability groups, Elite and Sub-Elite. Testing included kinanthropometric measurements, maximum aerobic capacity, pulmonary function, six core stability tests, a 30 min endurance performance test (EPT) on the K1 Ergo and a 10 km time trial (TT) on the water. Maximum inspiratory mouth pressure (MIP) was measured before and after the 30 min EPT on the K1 Ergo to assess respiratory muscle fatigue. The Elite paddlers demonstrated significantly greater values for sitting height (as a percentage of stature), relative VO2max, PPO, PPO/kg, MVV and MIP compared to the Sub-Elite paddlers (All P < 0.05). They also demonstrated a significantly greater average PO and average back stroke length during the 30 min K1 Ergo EPT (P < 0.05) and a significantly faster race time (44:10 ± 1:17 vs 47:34 ± 3:14 min:s) during the 10 km water TT (P < 0.05), compared to the Sub-Elite paddlers. The paddlers did not experience respiratory muscle fatigue (as determined by change in MIP) after the 30 min K1 Ergo EPT. Significant intraclass correlations coefficients of r = 0.81 for average PO (30 min K1 Ergo EPT), r = 0.76 for MIP, and r = 0.95 for 10 km performance time, revealed the high repeatability of these tests. Significant relationships were found between the two endurance performance tests (30 min K1 Ergo EPT and 10 km water TT, r = -0.64, P < 0.05) and between both tests and a number of kinanthropometric, physiological and respiratory muscle function parameters. Stepwise multiple regression analysis revealed that PPO and MVV predicted endurance performance (average PO) on the K1 Ergo (R2 = 0.75, SEE = 15 W), whereas relative VO2max and best MIP predicted 10 km performance time on the water (R2 = 0.64, SEE = 115 s). The results of this study suggest that superior maximum aerobic capacities and respiratory muscle function distinguish successful paddlers from less successful paddlers and may be used to predict kayak endurance performance in the laboratory as well as on the water. No respiratory muscle fatigue occurred during the 30 min K1 Ergo EPT, indicating that respiratory muscle fatigue may not be a limiting factor to 30 min kayak endurance performance. The core stability results demonstrated no relevance to kayak endurance performance.

This study was to clarify strength factors using 12 selected exercises on the Universal Gym, and to determine what measures present a valid method of assessing strength of college-aged males, Eighty-eight males enrolled in beginning weight-training classes used the Universal Gym for twelve weeks, Subjects were tested for maximum strength on 12 exercises, Alpha and canonical factor analyses were performed on raw scores of all measures, and on scores when body weight and standing height variances were removed. A three-factor structure of upper extremity, lower extremity, and trunk strength was revealed when weight, and weight and height combined were statistically controlled. Results showed that residualized scores of weight can be used to evaluate strength on the Universal.Gym,

The purpose of the present study was to investigate if any relationship exists between anthropometric measurements with average concentric velocity (ACV) at various intensities in the back squat and the number of repetitions able to be performed during a set to volitional fatigue at 70% of one-repetition maximum (1RM). It was hypothesised that short femurs and total height would be related to slower ACVs and lower total number of repetitions performed. 58 resistance trained subjects were recruited and attended one day of data collection. Subjects performed 1RM testing of the back squat followed by two single repetition sets at 30-90% of 1RM and a 70% of 1RM set to fatigue. There was no significant correlation between femur length and height with ACV at any intensity (p>0.05). A significant negative correlation existed between both height (r=-0.39, p=0.003) and femur length (r=-0.31, p=0.018) with total number of repetitions performed. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

[Truncated abstract] Resistance training is increasingly popular for improving strength qualities such as hypertrophy, maximal strength, endurance and power. Although many resistancetraining programmes now adhere to the concept of periodisation, the number of studies examining its structure and design are few, and there are just a handful of studies that have examined periodised training for the maintenance of strength and power. Even rarer, are periodised resistance-training studies that utilise female subjects. Previous studies have compared non-periodised training regimens such as Progressive Resistance Exercise (PRE), and the two main models of periodisation, Linear Periodisation (LP) and Undulating Periodisation (UP). Results are inconclusive as to whether the efficacy of the periodised training programmes were due to the manipulation of training variables such as volume and intensity, or that training programmes with higher doses of volume induced better training responses. However, to make effective comparisons between training programmes, the training volume or workload (total load lifted x total repetitions) and training intensity have to be equated between the groups under examination. While the intensities (percentage of one-repetition maximum, 1 RM) for improving strength qualities such as hypertrophy and maximal strength have general consensus among resistance-training practitioners, there exists disagreement over the intensity that should be used during the training of power. Thus, it is important to first identify the load for power training before comparisons can be made between LP and UP programmes using equal training volumes. ... The final study found that adhering to two UP maintenance training programmes with equalised volumes and intensities twice a week increased upper-body strength and maintained lower-body strength adequately across a 3-wk phase. The results from these studies support previous results that suggest training programmes with higher workloads and repetitions produce superior strength and power adaptations, and it is not specifically the variation of training volume and intensity within a periodised programme that improves strength qualities. Thus, both periodised programmes used in this thesis can be recommended for untrained and moderatelytrained women as both LP and UP were found to be similarly effective for increasing upper- and lower-body hypertrophy, strength and power.