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Concurrent Strength And Endurance Training Physical Education Essay

The fundamental training principle of specificity states that adaptations to exercise are highly dependent on the specific type of training performed (Kraemer and Ratamess, 2004, Baechle and Earle, 2008, Ratamess et al. 2009). Strength and endurance training produce widely diversified adaptations. Strength training typically results in increased force production capacity and/or increased muscle mass (Folland and Williams, 2007). In contrast, endurance training induces increases in maximal oxygen uptake (VO2max) and results in various metabolic adaptations that lead to an increase in work capacity (Wilmore and Costill, 2008). Despite these divergent adaptations physical training programs in fitness, athletic and rehabilitative settings often combine strength and endurance training concurrently in an attempt to achieve adaptations specific to both forms of training (Baechle and Earle, 2008). To date, research investigating physiological adaptations and performance improvements as a result of concurrent strength and endurance training has produced equivocal results. Hickson (1980) first proposed the existence of a possible “interference phenomenon” between concurrent strength and endurance training by demonstrating that strength gains were reduced when the two types of training were performed concurrently. A number of subsequently published studies have supported these findings demonstrating that concurrent strength and endurance training compromises both strength and/or power measures (Dudley and Djamil, 1985, Hennessy and Watson, 1994, Kraemer et al. 1995, Häkkinen et al. 2003, Rhea et al. 2008).

Table I. Studies demonstrating an interference effect upon strength and/or power measures

Study and population

Subjects

Study duration and frequency

Design variables

Findings

Hickson, (1980)

Sedentary males and females

S group:

7 males and 1 female

E group:

5 males and 2 females

C group:

5 males and 2 females

S group:

10 weeks

5 days·week-1

E & C groups:

10 weeks

6 days·week-1

S group: 2-3 exercises

80% 1 RM

5-20 repetitions·set-1

3-5 sets·exercise-1

E group: Cycle ergometer and running, maximum effort

30-40 minutes·session-1

C group: Combined S and E training with 2·hour rest period

S group greater ↑ in S than C

E group no ↑ in S

E⸗C groups ↑ VO2max

Dudley and Djamil, (1985)

Sedentary males and females

S group:

6 males and females

E group:

6 males and females

C group:

6 males and females

7 weeks

3 days·week-1

S group: 1 Isokinetic exercise MVC for 30 seconds

26-28 repetitions·set-1

3 sets·exercise-1

E group: cycle ergometer

5 sets of 5 minutes at or near peak VO2max

C group: S and E sessions performed on alternating days

S group ↑ peak torque at all velocities

C group ↑ peak torque at slower velocities (0 to 1.68 rads·s-1)

E⸗C groups ↑ VO2max

Hennessy and Watson, (1994)

Trained rugby players

S group: 9 males

E group: 12

males

C group: 10 males

8 weeks

S group:

3 days·week-1

E group:

4 days·week-1

C group:

5 days·week-1

S group: periodised program

70-105% 1 RM

E group: running

80-100% MHR

C group: combined S & E twice week, 1 day S and 2 days E

S and C groups ↑ upper body S

S group ↑ lower body S, 20m sprint time and vertical jump

E⸗C group ↑ VO2max

Kraemer et al. (1995)

Trained soldiers

S group:

9 males

E group:

9 males

UC group:

9 males

C group:

9 males

12 weeks

4 days·week-1

S group: heavy/light split routine

3 x 10 RM and 5 x 5 RM

E group: running, 80-100% VO2max

UC group: upper body S only and E same day

C Group: S and E training same day

S, UC and C groups ↑ upper body S

S group ↑ lower body S and anaerobic power E, UC and C groups ↑ VO2max

Häkkinen et al.(2003)

Recreationally trained males

S group:

16 males

C group:

11 males

21 weeks

S group:

2 days·week-1

C group:

4 days·week-1

S group: 6-7 exercises

50-80% 1RM

3-5 sets·exercise-1

8-12 repetitions·set-1

C group: cycle ergometer

continuous and interval training

30-90 minutes·exercise-1

S and C groups ↑ S

S group ↑ RFD

C group ↑ VO2max

Rhea et al. (2008)

Trained male Baseball players

S group:

8 males

C group:

8 males

18 weeks

2-3 days·week-1

S group: 4 exercises

4-12 sets·exercise-1

2-6 repetitions·set-1

plyometric and sprint training

2 days·week-1

C group: S training minus plyometric and sprint training

Continuous running or cycling 20-60 minutes·exercise-1

12-18 Borg RPE

S group ↑ vertical jump power

S = Strength; E = Endurance; C = Concurrent; RM = Repetition Maximum; MVC = Maximal Voluntary Contraction; MHR = Maximum Heart Rate; UC = Upper Body Strength and Endurance; RFD = Rate of Force Development; RPE = Rate of Perceived Exertion

However, several studies have refuted these findings by demonstrating no inhibitory effect on the development of strength (Sale et al. 1990, McCarthy et al.1995, Bell et al. 1997, Gravelle and Blessing, 2000, McCarthy et al. 2001, Balabinis et al. 2004, Shaw et al. 2009). Furthermore, a number of studies have demonstrated that the development of both strength and endurance may both be compromised as a result of concurrent training (Nelson et al. 1990, Glowacki et al. 2004). Adaptations to both strength and endurance training are dependent upon the length of training intervention, individual training status, age, gender, genetic predisposition and manipulation of the acute training variables (intensity, volume, exercise selection and order, rest periods between sets and frequency of training) (Baechle and Earle, 2008, Ratamess et al. 2009). From the literature reviewed it is difficult to compare results due to the markedly different study methodologies utilised which include variations in the age, gender and training status of the participants as well as substantial variations in the mode, frequency, duration and intensity of training (Tables I, II and III). However, based upon literature reviewed an interference effect upon the development of strength and/or power seems to hold true in certain situations. A variety of mechanisms have been proposed as to explain the observed interference phenomenon. Changes in muscle fibre type composition have been proposed as a possible mechanism for the inhibition of strength and subsequent power development (Dudley and Fleck, 1987). The power output of muscle fibre types (IIx > IIa > I) differs, thus different training variables may result in differing adaptations (Folland and Williams, 2007). Both strength and endurance training has been demonstrated to alter the ratio of type II muscle fibres, as the percentage of type IIa fibres increases and that of IIx fibres decreases (Folland and Williams, 2007).

Table II. Studies demonstrating no interference effect

Study and population

Subjects

Study duration and frequency

Design variables

Findings

Sale et al. (1990)

Sedentary males and females

S group: 4 males and 4 females

C group: 4 males and 4 females

22 weeks

3 days·week-1

S group: S one leg and C the other

C group: E one leg and C the other

S group: leg press

6 sets·exercise-1

15 – 20 repetitions·set-1

E group: cycle ergometer

90 – 100% VO2max

5 x 3 minute intervals

No interference of either S or E

McCarthy et al.(1995)

Sedentary males

S group:

5 males

E group:

5 males

C group:

5 males

10 weeks

3 days·week-1

S group: 8 exercises

5-7 repetitions·set-1

4 sets·exercise-1

E group: cycle ergometer, 50 minutes, 70% MHR

C group: Combined S and E same day

S and C groups ↑ S

E and C groups ↑ VO2max

Bell et al. (1997)

Male and female student rowers

S group:

6 males and 7 females

C group:

14 males and 8 females

16 weeks

3 days·week-1

S group: 8 exercises

65-85% 1 RM

2-10 repetitions·set-1

2-6 sets·exercise-1

C group: row ergometer, continuous and interval training, 90% VO2max

C⸗S group males ↑ lower body S

S group females ↑ lower body S

C group males ↑ in cortisol levels after week 8

Gravelle and Blessing, (2000)

Recreational active women

S group: 6 females

S & E group: 6 females

E & S group: 7 females

11 weeks

3 days·week-1

S group: 5-6 lower body exercises

2-10 repetitions·set-1

2-4 sets·exercise-1

S & E group: S training followed by row ergometer

45 minutes·exercise-1

70% VO2max

E & S group: E followed by S training

S, S & E and E & S groups ↑ lower limb S and VO2max

S & E groups ↑ anaerobic power

McCarthy et al. (2001)

Sedentary males

S group: 10 males

E group: 10 males

C group: 10 males

10 weeks

3 days·week-1

S group: 8 exercises

5-7 repetitions·set-1

4 sets·exercise-1

E group: cycle ergometer

50 minutes·exercise-1

70% MHR

C group: Combined S and E with 20·minute rest period

S and C groups ↑ muscle CSA and S

Balabinis et al. (2003)

Trained male basketball players

S group:

7 males

E group:

7 males

C group:

7 males

7 weeks

4 days·week-1

S group: 4 exercises

75-95% 1RM

1-5 sets·exercise-1

3-6 repetitions·set-1

plyometric training weeks 4-5

C group: Interval running

70-90% MHR

S and C groups ↑ S

C group ↑ anaerobic power

E and C groups ↑ VO2max

S = Strength; E = Endurance; C = Concurrent; RM = Repetition Maximum; MHR = Maximum Heart Rate; CSA = Cross Sectional Area

Table II. (Cont) Studies demonstrating no interference effect

Study and population

Subjects

Study duration and frequency

Design variables

Findings

Shaw et al.(2009)

Sedentary males

S group:

13 males

C group:

12 males

16 weeks

3 days·week-1

S group: 8 exercises

60% 1 RM

3 sets·exercise-1

15 repetitions·set-1

C group: Combination of running, rowing, stepping and cycling,

22 minutes·exercise-1

60% MHR

S and C groups ↑ in S

S = Strength; E = Endurance; C = Concurrent; RM = Repetion Maximum; MHR = Maximum Heart Rate

However, studies investigating changes in muscle type fibre composition as a result of concurrent strength and endurance training have demonstrated similar alterations in muscle fibre type as observed in either strength or endurance training alone (Sale et al. 1990, Nelson et al. 1990, Kraemer et al. 1994, McCarthy et al. 2001, Häkkinen et al. 2003). It has been suggested that concurrent strength and endurance training may disrupt patterns of muscle fibre hypertrophy normally associated with strength training. Strength training has been shown to increase muscle cross sectional area as a result of hypertrophy of type I, IIa and IIx muscle fibres whereas endurance training has been shown to result in hypertrophy of predominately type I fibres (Folland and Williams, 2007). Kraemer et al. (1995) demonstrated that strength training resulted in a significant increase in type I, IIa and IIx muscle fibres, while concurrent strength and endurance training resulted in an increase in type IIa fibres only. Conversely, several other authors have demonstrated no significant alterations in muscle fibre hypertrophy as a result of concurrent strength and endurance training (Sale et al. 1990, Nelson et al. 1990, McCarthy et al. 2001, Häkkinen et al. 2003). It has been proposed that concurrent strength and endurance training may interfere in the development of strength and/or power as a result of interference in various neural mechanisms (Dudley and Djamil, 1985, Chromiak and Mulvaney, 1990).

Table III. Studies demonstrating an interference effect upon both strength and endurance measures

Study and population

Subjects

Study duration and frequency

Design variables

Findings

Nelson et al. (1990)

Sedentary males

S group:

5 males

E group:

4 males

C group:

5 males

20 weeks

4 days·week-1

S group: 1 Isokinetic exercise MVC

6 repetions·set-1

3 sets·exercise-1

E group: cycle ergometer

70-85% MHR

30-60 minutes

C group: combined S and E training with 10·minute rest period

S and C groups similar increases in peak torque (0 to 180°/sec)

E group ↑ VO2max C group VO2max gains compromised during final 10 weeks of study

Glowacki et al. (2004)

Sedentary males

S group:

13 males

E group:

12 males

C group:

16 males

12 weeks

S and E groups:

2-3 days·week-1

C group:

5 days·week-1

S group: 8 exercises

75-85% 1RM

3 sets·exercise-1

6-10 repetitions·set-1

E group: running

20-40 minutes·exercise-1

S and C groups ↑ S

S group ↑ Vertical jump power

E group only ↑ VO2max

S = Strength; E = Endurance; C = Concurrent; MHR = Maximum Heart Rate; RM = Repetion Maximum

Strength training has been demonstrated to enhance both strength and power measures (Ratamess et al. 2009). Endurance training on the other hand has been demonstrated to reduce the capacity of the neuromuscular system to rapidly generate force (Leveritt et al. 1999) therefore; concurrent strength and endurance training may result in a similar inhibition. Several studies have demonstrated impairments in peak isokinetic torque (Dudley and Djamil, 1985,) rate of force development (Häkkinen et al. 2003) vertical jump (Hennessy and Watson, et al. 1994, Glowacki et al. 2004, Rhea et al. 2008) and 20m sprint performance (Hennessy and Watson, et al. 1994) suggesting a reduction in the ability of the neuromuscular system to rapidly generate force as a result of concurrent strength and endurance training. Dudley and Djamil (1985) suggested that concurrent strength and endurance training may result in altered motor unit recruitment patterns. However, no study conducted thus far has investigated training induced changes in motor unit recruitment patterns.

Attenuated improvements observed in strength and power as a result of concurrent strength and endurance training may possibly be attributed to the development of residual fatigue in the neuromuscular system. Residual fatigue may compromise the ability of the neuromuscular system to develop force which in turn may lead to a reduced training stimulus and subsequent training-induced adaptive response in comparison to strength training alone. Residual fatigue has been proposed to be the result of central and peripheral mechanisms (Enoka, 1995). Gandevia (1998) suggests that during sustained muscle contractions, the discharge of motor neurons declines below the level necessary to produce maximal force. Most importantly, Gandevia reports that the brain’s motor cortex shows evidence of reduced output during fatigue supporting the notion of central neural fatigue. A number of studies have suggested that strength development is only impaired in muscle groups which are utilised during both strength and endurance training suggesting that the effects of residual fatigue may be localised to concurrently trained muscle groups supporting the concept of peripheral fatigue (Hennessy and Watson, 1994, Kraemer et al. 1995). Possible causes of peripheral fatigue may include muscle tissue damage, accumulation of metabolites and depletion of energy substrates such as adenosine tri-phosphate, creatine phosphate and muscle glycogen (Bishop, et al 2008). Typical concurrently trained groups often perform double the total training volume of either the strength or endurance trained groups. Studies which have employed a relatively high training frequency and volume (4-6 d·wk-1) over both short (<7·wk) and long term (>20·wk) training interventions have demonstrated an inhibition in the development of strength, power and/or endurance in concurrently trained groups (Hickson, 1980, Nelson el at. 1990, Hennessy and Watson, 1994, Kraermer et al. 1995, Häkkinen et al. 2003 and Glowacki et al. 2004).

However, a number of studies which have employed a low training frequency and volume (2-3 d·wk-1) over both short term (<7·wk) and long term (>22·wk) training interventions have demonstrated a possible synergistic effect with positive adaptations in both strength and endurance measures (Sale et al. 1990, McCarthy et al. 1995, Bell et al. 1997, Gravelle and Blessing, 2000, McCarthy et al. 2001, Balabinis et al. 2003, Shaw et al. 2009). Indeed, recent research has indicated that a training induced adaptive dose-response relationship may exist suggesting that there may be an optimal volume of training in which to induce positive adaptive responses (Peterson et al. 2005). It has been proposed that concurrent strength and endurance training may produce an ‘overtraining’ state such that the training stimulus exceeds the maximal adaptive response of a given physiological system (Kraemer and Nindl, 1998). Recovery from training has been stated as being one of the most important aspects of improving athletic performance (Bishop et al. 2008). Thus, repeated exposure to a training stimulus without adequate recovery may to lead to overtraining typically characterised by a either a stagnation or decline in performance (Bishop et al. 2008). Indeed, from the literature reviewed stagnation was observed in the development of strength and/or power measures in a number of concurrent training studies (Dudley and Djamil, 1985, Hennessy and Watson, 1994, Kraemer et al. 1995, Häkkinen et al. 2003, Rhea et al. 2008). It may be argued that if this is indeed the case then both strength and endurance measures would be inhibited. This argument presumes that the thresholds for the effects of overtraining to become apparent for strength and endurance measures are similar. However, only two studies demonstrated an interference effect in the development of strength and endurance measures (Nelson et al. 1990, Glowacki et al. 2004).

Recent research examining the genetic and molecular mechanisms of adaptation induced by strength and endurance training has demonstrated that each mode of exercise activates and/or represses a specific subset of genes and cellular signalling pathways (Hawley, 2009). Strength training has been proposed to increase anabolic signalling mechanisms resulting in a proportionate increase in the rate of protein synthesis greater than that of protein breakdown whereas, endurance training has been proposed to result in more energy-modulating metabolic signalling mechanisms resulting in increased mitochondrial and oxidative enzyme activity (Hawley, 2009). Nader (2006) proposed that concurrent strength and endurance training and/or too-frequent training sessions may result in an antagonistic relationship, interfering with activation/inhibition of these signals altering the subsequent adaptive response thus, a relatively high frequency of concurrent strength and endurance training may result in a interference effect. From the literature reviewed it is difficult to draw conclusions due to the varying methodologies utilised. However, an interference effect seems to hold true when a relatively high volume and frequency of concurrent strength and endurance training is performed. At present a variety of hypotheses has been proposed to explain the observed interference phenomenon. Recent evidence suggests that the cumulative effects of residual fatigue and/or interference of the genetic and molecular mechanisms of adaptation may result in a reduced adaptive response in comparison to strength or endurance training alone. In summary, concurrent strength and endurance training may result in a potential interference effect. However, a periodised training program designed to systematically manipulate the training variables and incorporating appropriate recovery strategies may result in a possible synergistic effect with positive adaptations in both strength and endurance measures.

Total Word Count – 3014 / 3000

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