Foreword

Over the last several years exercise has been included in the daily program of most people since knowledge of its beneficial effects are spread worldwide. Through exercise people improve their health, robustness, well-being and generally their quality of life. Robustness is important in order for the body to function effectively. The components that constitute robustness are: bodily constitution, cardiovascular robustness, flexibility and muscular robustness. Muscular robustness is constituted by two components: strength and the muscular endurance. The probability of suffering from injury in the joints is significantly less in an individual who attains muscular robustness (Corbin, Lindsey and Welk, 2000). Strength is defined as the ability of the muscle to work. Maximum strength is sometimes defined as the greatest possible weight that a muscle or a group of muscles can lift for maximum repetitions. It is also reported that maximum strength is fixed as the biggest possible strength that the neuromuscular system can develop with maximum constriction (McArdle, Katch and Katch, 2000).

Muscular endurance is the muscle’s ability for endurance to tiredness of strength or the ability of maintaining a percentage of strength. Endurance of strength is fixed as the ability of the body to resist tiredness for long periods of time (McArdle, Katch and Katch, 2000; Fleck and Kraemer, 2004). Training of strength mainly increases the size of quick twitch fibres while the medium fibres increase also in size but not in that extent. At the training of muscular endurance, the muscles are adapted via changes in the fibres of slow constriction as well as of increased activity of their aerobic muscular ferments. According to the American College of Sports Medicine (2002), progressive overloading is the continuous increase of workload on the body, “tolerance in continuously increasing charges of” which is vital for progress in a program. In fact the body continues to adapt as long as it is given stimuli of a higher workload than of what it is used to.

There are many ways to increase the work load: (1) Increasing the endurance, (2) Increasing the repetitions in a given resistance, (3) Changing the speed of repetitions depending on the objectives, (4) Reduction of breaks in order to improve the endurance in the strength, (5) Increasing the training volume, (6) Giving variety of skills (ACSM, 2002). Training involves continuous changes (adaptations) that vary from the level of training, the experience and the genetic characteristics of each individual. Untrained individuals showed adaptations to most programs, something that renders it difficult to appreciate the value of each different program. The level of improvement in trained individuals was much slower comparing to those untrained (ACSM, 2002).

Concerning the resistance, 45-50% muscular endurance (ME) has been found to increase the maximum strength in untrained people. For trained people at least 80% ME resistance was needed in order to have greater neuromuscular adaptations. Many advanced studies showed that 1-6 ME, were the most effective for the increase of maximum strength, even though increases of strength were also observed with 8-12 ME. Moreover it has been found that a variety in the resistance brought better results than the utilisation of only one repetition in the long run (ACSM, 2002). The increase of muscular strength depended to a great extent from the volume of the training. The volume of the training depended on the number of exercises that occurred, the number of repetitions in each set and/or the number of sets in each exercise. Researches of Dudley and Djamil (1985) used two sets per exercise of 30 repetitions in isokinetic dynamometer; also Kraemer (1997) and Staron (1994), used three sets per exercise, and observed important increases in the maximum strength.

In order to have improvement of muscular endurance a higher volume of training has been shown to be more effective (Iickson, Hidaka and Foster, 1994; Kraemer, 1997). In this case, it was recommended that a break of 1-2 minutes should be taken for every 15 repetitions or more and less than 1 minute for every 10-15 repetition. Participants that trained for increase of muscular endurance appeared to be more effective when they used a set with a lot of repetitions and small periods of rest (30 seconds-90 seconds or even less) (Anderson and Kearney, 1982). In research conducted by Campos, Gerson, Luecke, Wendeln, Toma and their colleagues (2002), 32 untrained men took part and were separated into 4 experimental groups. A group executed 3-5 maximum repetitions of 4 sets in each exercise with a resting time between the sets to be 3 minutes. There was also an intermediary group, who had performed 9-11 maximum repetitions of 3 sets with 2 minutes break, while there was another group who did a high number of maximum repetitions (20-28) of 2 sets with 1 minute break. Three exercises were done (leg press, seats and leg extension) with a frequency of 2 times per week for the first 4 weeks and 3 times per week for the last 4 weeks. The group that executed few maximum repetitions showed better results in the measurement for increasing maximum strength, than the group that executed a high number of maximum repetitions. In contrary in the measurement for muscular endurance the group that executed a high number of maximum repetitions showed better results than the group that executed few maximum repetitions in all exercises. In another research where untrained men participated and were trained 3 times per week for an interval of 12 weeks, no differences occurred in the maximum strength when the trained volume and the intensity were equal. Participants were divided into 3 different trained groups where the intensity and the trained volume were equal (Baker, Wilson and Carlyon, 1994). In untrained participants where circular training was used with weights for interval of 10 weeks with a frequency of 3 times per week, significant increase in maximum strength was observed (1 RM) in 9 from 10 exercises (15-42%) (Harber, Fry, Rubin, Smith, and Weiss, 2004).