Scand J Med Sci Sports 2014: 24 (Suppl. 1): 76–85 doi: 10.1111/sms.12245

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Effect of football or strength training on functional ability and physical performance in untrained old men T. R. Andersen1, J. F. Schmidt1,2, J. J. Nielsen1, M. B. Randers1, E. Sundstrup3,5, M. D. Jakobsen3,5, L. L. Andersen3, C. Suetta4, P. Aagaard5, J. Bangsbo1, P. Krustrup1,6 1

Copenhagen Centre for Team Sport and Health, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark, 2Department of Cardiology, Gentofte Hospital, Gentofte, Denmark, 3The National Research Centre for the Working Environment, Copenhagen, Denmark, 4Department of Diagnostics, Section of Clinical Physiology and Nuclear Medicine, Glostrup Hospital, Copenhagen, Denmark, 5Institute of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense, Denmark, 6Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK Corresponding author: Peter Krustrup, PhD, Department of Nutrition, Exercise and Sports, University of Copenhagen, Universitetsparken 13, Copenhagen DK 2100, Denmark. Tel: +0045 35 32 16 24, Fax: +0045 35 32 16 00, E-mail: [email protected] Accepted for publication 24 March 2014

The effects of 16 weeks of football or strength training on performance and functional ability were investigated in 26 (68.2 ± 3.2 years) untrained men randomized into a football (FG; n = 9), a strength training (ST; n = 9), or a control group (CO; n = 8). FG and ST trained 1.6 ± 0.1 and 1.5 ± 0.1 times per week, respectively, with higher (P < 0.05) average heart rate (HR) (∼ 140 vs 100 bpm) and time >90%HRmax (17 vs 0%) in FG than ST, and lower (P < 0.05) peak blood lactate in FG than ST (7.2 ± 0.9 vs 10.5 ± 0.6 mmol/L). After the intervention period (IP), VO2max (15%; P < 0.001), cycle time to exhaustion (7%; P < 0.05), and Yo-Yo Intermittent Endurance Level 1

performance (43%; P < 0.01) were improved in FG, but unchanged in ST and CO. HR during walking was 12% and 10% lower (P < 0.05) in FG and ST, respectively, after IP. After IP, HR and blood lactate during jogging were 7% (P < 0.05) and 30% lower (P < 0.001) in FG, but unchanged in ST and CO. Sit-to-stand performance was improved (P < 0.01) by 29% in FG and 26% in ST, but not in CO. In conclusion, football and strength training for old men improves functional ability and physiological response to submaximal exercise, while football additionally elevates maximal aerobic fitness and exhaustive exercise performance.

In aging subjects, an improvement in individual physical capacity is positively related to overall physical function (Christensen et al., 2006), as well as the ability to carry out activities of daily living (ADL) such as walking and getting up from a chair (Leveille et al., 1999; Spirduso & Cronin, 2001). Also, aging is associated with a decline in skeletal muscle performance and maximal oxygen uptake (VO2max), and as these factors are highly modifiable by training, regular exercise may be a key element for successful and healthy aging (Garber et al., 2011). Loss in muscle mass and strength, commonly referred to as sarcopenia, adds to the limitations in physical function and performance with aging (Vandervoort, 2002; Narici & Maffulli, 2010), and subjects with low leg muscle strength have been shown to experience three times as many problems related to ADL than subjects with high leg muscle strength (Brill et al., 2000). Aging is furthermore accompanied by progressive degenerative alterations in neural function, which strongly influences the function of the neuromuscular system (Aagaard et al., 2010). Several types of ADL tasks, such as stair

walking or avoiding tripping over obstacles, require the ability to rapidly develop muscle force (Bassey et al., 1992), and it can therefore be important for senior citizens to engage in exercise activities that improve explosive muscle properties and stimulates to increases in muscle mass, strength, and endurance (Caserotti et al., 2008; Aagaard et al., 2007, 2010). Traditionally, endurance-like strength training with moderate to low loads has been used to obtain such muscular adaptation in the aging subject, but high-intensity strength training (≥80% of 1 repetition maximum; 1RM) has recently been proven superior for improving muscle strength and functional capacity, such as chair raising, stair walking, and 6-min walking performance, compared with low-tomoderate-intensity resistance training (40% of 1RM) (Seynnes et al., 2004). Along the same line, 12 weeks of explosive type heavy-resistance strength training in 80-year-old women caused explosive muscle strength characteristics (rate of force development; RFD) to reach levels observed in 60-year-old untrained women, illustrating the possible magnitude of functional

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Performance enhancements in veteran football juvenilization that can be achieved with high-intensity exercise in old adults (Caserotti et al., 2008). A decrease in VO2max is typically observed with physiological aging (Hollenberg et al., 2006), and crosssectional studies have shown that untrained subjects generally experience a 5–10% drop in VO2max per decade from the age of 20 (Talbot et al., 2000). Interestingly, a meta-analysis concluded that a healthy but physically inactive 67-year-old person could expect to improve VO2max by approximately 3.8 mL/kg/min after 4–5 months of moderate-intensity exercises performed three times per week (Fleg et al., 2005). Given that VO2max fluctuations of 5 mL/kg/min approximately correlate with a 10-year change in biological age (Shephard, 2007), engagement of aging subjects in training interventions with the ability to improve VO2max within this range may prove vital for the maintenance of an independent lifestyle throughout the life span. The physical activity recommendations for aging subjects includes a minimum of 150 min of moderate intensity or 60 min of vigorous physical activity per week (Nelson et al., 2007), and resistance training recommendations for older adults comprises 10–15 repetitions of 8–10 exercises that involve major muscle groups at moderate to high intensity at least twice per week (Kraemer et al., 2002; Nelson et al., 2007). The greatest benefit is seen in inactive adults and normally active adults, indicating that even a small increase in physical activity can produce large gains, and furthermore, that a combination of resistance and aerobic training seems to be more effective than either of the training forms alone (Chodzko-Zajko et al., 2009), also in terms of improved health-related quality of life (Sillanpaa et al., 2012). However, as covered in details by Nielsen et al. (2014), engagement in multiple weekly exercise regimen settings may not be applicable to the aging population due to e.g., travelling distances and economic constraints. Thus, the need for further elucidation of new training alternatives (e.g., football training, which does not require expensive equipment and can be played almost everywhere) may be of vital importance for the physical activity levels in aging subjects for the future to come. In recent years, the physiological response and health benefits of recreational football have been comprehensively investigated (Krustrup et al., 2010). These studies have revealed that small-sided football is an intense and variable type of interval training that is highly suitable for untrained young and middle-aged participants irrespective of technical skills and results in valuable broad-spectrum improvements in fitness and physical performance (Krustrup et al., 2010). With respect to the aging subject, recreational football has been shown to stimulate both the aerobic and anaerobic energy systems, as indicated by high heart rates and elevated blood lactate levels during training for players with life-long participation in football (Tessitore et al., 2005; Randers et al., 2010). The 65–75-year-old players with life-long

participation in football were also shown to have remarkable postural balance and superior mechanical muscle function along with better cardiac function, exhaustive exercise performance, and much healthier body composition than age-matched untrained elderly persons (Aagaard et al., 2007; Sundstrup et al., 2010; Schmidt et al., 2013a). Thus, recreational football training may serve as an important alternative to training modalities traditionally applied to maintain physical function, health, and longevity in the aging population such as strength and endurance training (Gremeaux et al., 2012). Previously, studies from our research group have compared the performance effect of recreational football with that of continuous moderate-intensity running in untrained young men and premenopausal women (Krustrup et al., 2009; Bangsbo et al., 2010), but controlled and randomized studies applying football training to a healthy aging population have not previously been carried out. Also, the effect of football training in comparison with strength training, as a performanceenhancing training measure as well as the acute metabolic response to this kind of training has not been investigated in old untrained male subjects. As such, the present study adds knowledge on how football can be used as an activity to improve mobility function and as a performance in men aged 65–75 years of age. Hence, the aim of the present study was to determine the effects of 16 weeks of recreational football training or progressive strength training on submaximal and maximal aerobic exercise performance, as well as physical function, explosive muscle performance, and intermittent endurance capacity in old (+65 years) untrained male subjects, and to examine the acute physiological response to small-sided games football training or strength training in elderly untrained subjects. Materials and methods Subjects Twenty-six healthy old male subjects [age: 68.2 ± 3.2 years (range: 63–74) years] were recruited via advertisements in local newspapers and randomly assigned to either a football training group (FG) (n = 9), a strength training group (ST) (n = 9), or an inactive control group (CO) (n = 8) stratified for body mass index and maximal oxygen uptake (VO2max). Medical screening was performed before the start of the intervention period. None of the subjects were on medication, and none were smokers. With the exception of one subject, who was a recreational golfer, none of the subjects had been involved in regular physical exercise training during a major part of their adult life, and according to their recollection, the past 5–10 years could be characterized as being mainly inactive. Exclusion criteria were symptoms or history of cardiovascular disease, hyperglycemia, or diagnosed hypertension. No group differences were detected in pre-intervention values for FG, ST, and CO with regard to age [68.0 ± 4.0 (± SD) vs 69.1 ± 3.1 vs 67.4 ± 2.7 years], body weight (77.7 ± 9.4 vs 85.8 ± 12.0 vs 89.3 ± 12.4 kg), height (173.3 ± 7.8 vs 176.7 ± 9.8 vs 179.0 ± 6.2 cm), body mass index (26.1 ± 3.9 vs 27.4 ± 2.8 vs 27.9 ± 4.6 kg/m2), and VO2max (27.5 ± 5.4 vs 28.9 ± 5.5 vs 30.8 ± 3.3 mL/min/kg). During the initial phase of IP, one subject from FG was recorded as a dropout because of an Achilles tendon

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Andersen et al. tear. Data from this subject have been excluded from all study analysis. Further, details of subject recruitment and randomization have been described elsewhere (Schmidt et al., 2014). All subjects were informed of potential risks and discomforts associated with the experimental procedures before giving their written informed consent to participate. The study conformed to the code of ethics of the World Medical Association (Declaration of Helsinki) and was approved by the local ethical committee of Copenhagen (H-1-2011-013). The study was reported at ClinicalTrials.gov.: NCT01530035.

corresponding to a training adherence of 77.1 ± 2.4 vs 74.1 ± 2.4% in FG and ST, respectively, which was the same (P > 0.05) for the two groups.

Measuring and test procedures The subjects were familiarized with all protocol procedures prior to the testing sessions at the beginning of IP. No strenuous physical activities were performed 2 days before a testing session, and intake of caffeine and alcohol on the day of the experiment was avoided.

Experimental design The present study represents an independent part of a comprehensive interventional protocol investigating cardiovascular and musculoskeletal adaptations as well as changes in physical performance, health status, and psychological quality of life in the study participants. This paper focuses specifically on changes to performance and physical function, whereas the effects of strength training and football training on muscle tissue adaptations will be addressed elsewhere. The subjects in FG and ST performed supervised training sessions for 1 h twice a week for 16 weeks, whereas the subjects in CO were instructed to continue with their daily routines and not change lifestyle during IP. Testing sessions were performed at the start of IP (0 week) and after 16 weeks to investigate the effects of football or strength training. For all subjects, the testing protocol included blood sampling and recordings of pulmonary gas exchange during a standardized submaximal aerobic exercise protocol as well as during an incremental cycling test performed to exhaustion for determination of maximal aerobic power (VO2max). Also, maximal intermittent endurance capacity (Yo-Yo intermittent endurance level 1 performance; IE1) was determined before and after IP. To address strength adaptations, maximal jumping performance, and repeated chair raising ability were determined before and after the training period. In FG and ST, additional measurements (blood and muscle samples) were performed during a selected session to establish the metabolic response to training.

Training intervention In FG, the training sessions consisted of small-sided (four-a-side, five-a-side, six-a-side) games performed on a natural grass pitch. During the first 12 weeks of IP, training was organized as 3 × 15min exercise periods separated by 2-min rest periods. In weeks 13–16, training was organized as 4 × 15-min exercise periods separated by 2-min rest periods. In ST, training consisted of a 5-min low-intensity warm-up protocol followed by five strength training exercises (leg press, seated leg extension, prone hamstring curl, pull-down, lateral dumb-bell raises or equivalent) in addition to 5 min of core training (crunches and back extensions or equivalent) performed at the end of each training session. During the first 12 weeks of IP, training was organized as three sets per exercise separated by 1.5-min rest periods. In weeks 13–16, training was organized as four sets per exercise periods separated by 1.5-min rest periods. During weeks 0–4, weeks 5–8, weeks 9–12, and weeks 13–16 of IP, strength training intensity was progressed as 16–20 reps (16–20 RM), 12 reps (12 RM), 10 reps (10 RM), and 8 reps (8 RM), respectively, with a focus on maximal intentional acceleration of the training load during the concentric part of the movement (Caserotti et al., 2008). Each set was performed with the heaviest possible (RM) load without compromising safety and lifting technique. During the intervention period, the total number of training sessions and the number of training session per week was the same (P > 0.05) in FG and ST (25.1 ± 0.8 vs 23.3 ± 1.1 sessions; 1.6 ± 0.1 vs 1.5 ± 0.1 sessions per week, respectively),

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Submaximal and maximal cycling exercise testing Before as well as after IP, all subjects performed a standardized exercise protocol consisting of 4-min of treadmill walking (4.5 km/h) and 4 min of jogging (7.0 km/h) separated by a 2-min period of passive rest, followed by 2-min of passive rest and finally an incremental cycling test to exhaustion. During the incremental cycling test, subjects started exercising at a work pace and load of 80 rpm and 40 W, respectively, after which the work load was increased by 20 W every 2-min until volitional fatigue. Pulmonary gas exchange (OxyconPro; VIASYS Healthcare, Hoechberg, Germany) and heart rate (HR; Polar Team System, Polar Electro Oy, Kempele, Finland) were measured continuously throughout the exercise protocol, and a blood sample for determination of blood lactate were measured after each exercise bout via an antecubital arm vein. VO2max was determined as the highest value achieved during a 30-s period, and the time to exhaustion (TTE) during the incremental test was noted. The individual maximal heart rate (HRmax) was determined as the highest value measured within a 15-s period during all testing sessions of the study protocol.

Performance testing On separate occasions before and after 16 weeks, the subjects carried out a Yo-Yo IE1 test (Bangsbo, 1995). Briefly, the Yo-Yo IE1 test consisted of repeated 2 × 20 m runs at a progressively increased speed controlled by audio bleeps from a pre-recorded source. Between each running bout, the subjects had a 5-s rest period. The test result is recorded as the distance covered at the point when a subject has failed twice to reach the finishing line in the allocated time. The subjects also performed a jump test to assess maximal vertical jump height as a surrogate measure of explosive muscle power (Wisloff et al., 2004). This was assessed on a force platform (AMTI OR6, Watertown, MA, USA) in five single bilateral countermovement jumps (CMJ) interspersed with 30-s rest. The CMJ is characterized by an eccentric pre-stretch phase followed by a propulsive concentric phase characterized by a downward and upward movement of the body’s center of mass, respectively. The subjects were instructed to jump as high as possible with their hands placed on their hips. The highest jump was selected for statistical analysis. The vertical force signal (Fz) was analyzed as described in detail elsewhere (Jakobsen et al., 2012; Jay et al., 2013). In brief, the vertical velocity (V) of the center of mass was obtained by time integration of the instantaneous acceleration (Fz/m – g, where m = body mass in kg and g = 9.81/m/s2), and the center of mass position was obtained by subsequent time integration of V. Maximum jump height was derived from the vertical take-off velocity (Vto) using the equation jump height = Vto2/(2g), where g = 9.82 m/s2. To determine the effect of football or strength training on functional mobility, the subject’s ability to perform repeated chair raises was determined using a standardized sit-to-stand (STS) test. Using a chair fixed to the ground with a seat height of 43 cm above ground, the subjects are instructed to sit in the middle of the chair with their back

Performance enhancements in veteran football straight, their arms crossed over chest, and their feet flat on floor. The correct technique was demonstrated to the participants first slowly, then quickly. The subjects practiced two to three repetitions before the start of the test. On the signal “go,” the subject rises to a full standing position, then returns to a seated position, and repeats this as many times as possible in 30 s (Jones et al., 1999).

ANOVA. Between-group and within-group changes after 16 weeks were analyzed using a two-way repeated-measures ANOVA. When a significant overall effect was detected, the Student–Newman– Keuls post-hoc analysis was applied to determine differences between different time points. P < 0.05 was chosen as the level of significance. Statistical analyses were performed using Sigma Plot (Systat Software Inc., San Jose, CA, US), version 11.0.

Physiological measurements during training

Results Physiological response to football and strength training

In FG and ST, HR was recorded at 1-s intervals using a HR monitor (Polar Oy) during each training session to detect changes in HR response to training during the intervention period. Data were later transferred to a computer for subsequent analysis using the Polar Team 2 system software (Polar Oy), and the data were pooled to yield average weekly HR response to training. HR responses during week 1 and week 16 are presented.

Muscle biopsy and blood sample collection On one occasion during the intervention period (after 16 weeks), to establish the acute metabolic response to a football or a strength training session, the subjects in FG and ST had a catheter inserted into an antecubital vein for concurrent collection of blood samples. Blood samples were collected after a low-intensity warm-up before the start of training, after each 10 min playing period, and 10 min into recovery from the previous playing period. Also, a biopsy was collected at rest and again at the end of the training session from m. vastus lateralis under sterile conditions and local anesthesia (1% lidocaine, Amgros 742122, Copenhagen, Denmark) using the Bergstrom technique (Bergstrom, 1962), and immediately frozen (−80 °C) in liquid nitrogen. The biopsy at rest was collected 48–72 h after a preceding training session, between 07:00 h and 10:00 h, and under standardized conditions after an overnight fast.

During training in week 1 and week 16, respectively, FG demonstrated higher (P < 0.001) mean HR during their exercise (138 ± 3 and 143 ± 3 bpm) than ST (93 ± 2 and 103 ± 3 bpm), corresponding to 81 ± 2 and 84 ± 1%HRmax in FG and 57 ± 2 and 61 ± 3%HRmax in ST. In FG, peak HR during training in week 1 and week 16 was 92 ± 2 and 93 ± 1%HRmax with lower (P < 0.01) values in ST (76 ± 2 and 82 ± 2%HRmax). In FG, time spent >90%HRmax was higher (P < 0.01) in week 1 and week 16 (16 ± 6 and 18 ± 7%) compared with ST (0 ± 0% and 0 ± 0%) (Fig. 1a,b). (a)

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The frozen samples were weighed before and after freeze-drying to determine water content. The samples were then dissected free of all visual connective tissue and blood by light microscopy (Stemi 2000-C, Zeiss, Oberkochen, Germany) at a room temperature of 18 °C and a relative humidity < 30%. The muscle tissue of dry weight samples was analyzed for muscle lactate fluorometrically and glycogen using the hexokinase method (Lowry & Passonneau, 1972).

Statistical analysis Group differences before IP were analyzed using a one-way analysis of variance (ANOVA). HR and blood data obtained during a training session were analyzed using a one-way repeated-measures

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Blood analyses Blood samples collected during training were immediately stored on ice and subsequently analyzed for blood lactate using an ABL 800 Flex (Radiometer, Copenhagen, Denmark). Part of this blood sample was rapidly centrifuged for 90 s. Plasma was collected and stored at –20 °C, and subsequently analyzed for plasma free fatty acids (FFA) and potassium using a fluorometric enzymatic kit (WAKO Chemicals GmbH, Neuss, Germany) and an ion-selective electrode, respectively (Hitachi 912 Automatic Analyzer; Roche Diagnostics, Indianapolis, IN, USA).

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Fig. 1. Heart rate distribution (weekly average) during training in FG (a) or in ST (b) during the first (filled bars) and the last week (open bars) of the intervention period in elderly adult males (n = 9) Mean ± SEM are presented. *Significantly (P < 0.05) different from week 1. $$$FG significantly (P < 0.001) different from ST.

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Andersen et al. Blood metabolite responses during a selected training session in FG and ST are presented in Fig. 2. Briefly, blood lactate concentration increased (P < 0.05) from 2.0 ± 0.3 and 1.5 ± 0.1 mmol/L to 2.9 ± 0.5 and 3.7 ± 0.4 mmol/L after 10 min of training in FG and ST, respectively, and remained elevated throughout the training session (Fig. 2a), with mean values of 4.6 ± 0.7 and 6.7 ± 0.6 mmol/L, respectively, in FG and ST (P = 0.07). Peak lactate levels in ST were 10.5 ± 0.6 mmol/L, which was higher (P < 0.05) than FG (7.2 ± 0.9 mmol/L) (Fig. 2a). In FG, plasma FFA increased (P < 0.05) twofold from rest to 30 min of training and remained elevated (Fig. 2b). Peak FFA level were higher (P < 0.01) in FG compared with ST (1047 ± 135 vs 423 ± 78 μmol/L, respectively). In ST, plasma FFA was unaltered (P > 0.05) during training. Plasma potassium was unchanged (P > 0.05) during training in both FG

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Performance changes In FG, after 16 weeks of training, TTE during the incremental cycling test was 7% longer (P < 0.05) (804 ± 36 vs 751 ± 28 s), and VO2max was 15% higher (P < 0.001) compared with before IP (Fig. 3a). In ST and CO, TTE and VO2max were not changed (Table 1). Yo-Yo IE1 performance was 740 ± 198 m after 16 weeks of training in FG, which was 43% better (P < 0.01) than before training (Fig. 3b). No changes in Yo-Yo IE1 performance were observed in ST and CO after 16 weeks (Fig. 3b). After IP, Yo-Yo IE1 performance changed more (P < 0.05) in FG compared with CO (43 vs −5%). STS performance was similar (P > 0.05) in FG, ST, and CO before IP, and STS performance improved (P < 0.01) 29% after 16 weeks from 17 ± 1 to 22 ± 1 repetitions in FG and by 26% in ST from 19 ± 1 to 24 ± 2 repetitions, while it was unaltered in CO (Fig. 3c). After IP, the change in STS performance was greater (P < 0.05) in FG and ST compared with CO (34 ± 12 and 29 ± 9 vs 3 ± 10%) with relative change in STS being similar in FG and in ST, although a tendency for a greater change was observed in FG (P = 0.09). In all groups, CMJ performance was the same at 0 and 16 weeks being 11.6 ± 1.6 and 13.4 ± 1.7 cm, respectively, in FG, 9.6 ± 0.6 and 11.3 ± 1.3 cm in ST, and 14.6 ± 1.3 and 13.4 ± 1.4 cm in CO.

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Fig. 2. Blood variables during training in FG (filled circles) and ST (open circles); blood lactate (a), plasma FFA (b) and plasma K+ (c). *Significantly (P < 0.05) different from 0 min. #Significantly (P < 0.05) different from values during training in FG and ST. $FG significantly (P < 0.05) different from ST. $$ FG significantly (P < 0.01) different from ST.

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and ST, with peak values of 6.7 ± 0.5 and 6.3 ± 0.3 mmol/L (P > 0.05) in FG and ST, respectively (Fig. 2c). Muscle glycogen content was reduced (P < 0.01) during training from 461 ± 34 to 359 ± 50 mmol/kg dw in FG and from 486 ± 31 to 394 ± 33 mmol/kg dw in ST. At the end of the training session, muscle lactate was higher (P < 0.001) in ST compared with before the session (38.0 ± 6.2 vs 10.1 ± 1.1 mmol/kg dw, n = 8), whereas in FG, muscle lactate was non-significantly (P = 0.166) higher at the end compared with before the training session (22.1 ± 3.1 vs 14.8 ± 2.8 mmol/kg dw, n = 5).

In FG, HR during walking at 4.5 km/h was 12% lower (P < 0.001) after IP compared with before training, and also lower (10%) in ST (Table 1). In FG, HR (7%) and blood lactate (30%) during running at 7.0 km/h were lower (P < 0.05) in FG after 16 weeks compared with 0 week, whereas no changes were observed in ST (Table 1). In CO, no changes were observed in HR or blood lactate response to either walking or submaximal running. In all groups, VO2, ventilation, and respiratory exchange ratio (RER) during walking and submaximal exercise were unchanged after 16 weeks.

Performance enhancements in veteran football (a)

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Fig. 3. VO2max (a), Yo-Yo IE1 performance (b), and sit-tostand performance (c) before (filled bars) and after (open bars) the 16-week intervention period for FG, ST, and CO **Significantly (P < 0.01) different from 0 week. ***Significantly (P < 0.001) different from 0 week.

Discussion The present study is the first to investigate the acute physiological response to recreational football training in 63–74-year-old untrained men, and to evaluate the effects of a 16-week football intervention vs strength training on functional ability and exercise performance. The main findings were that small-sided football training is an intense interval activity that elicits high HRs as well

as periods with high anaerobic energy turnover and musculoskeletal impact for untrained old men. Further, football training for a 16-week period appears to improve functional ability as well as submaximal and exhaustive aerobic exercise performance and intermittent exercise performance, even in old males with little or no prior experience of football. Moreover, strength training was observed to elicit high anaerobic energy turnover but only low-to-moderate HRs and resulted in positive training effects on functional ability and submaximal exercise performance, and with no major changes in aerobic fitness and exhaustive cycle performance. When untrained 63–74-year-old men are performing their first small-sided football training session for decades, average HRs lie around 80% HRmax and 17% of the session is spent in the aerobic high-intensity zone above 90% HRmax (Bangsbo et al., 2006). In contrast, the present data show that HRs were around 60% HRmax during a strength training session, with no time spent in the aerobic high-intensity zone. These HRs are highly comparable with values observed during smallsided football training for untrained 35–55 year-old men (Krustrup et al., 2013; Schmidt et al., 2013b), and slightly lower than for 50–65- and 65–75-year-old trained men during small-sided football training and match-play, with average HR of ∼ 85% HRmax and with 25–45% above 90% HRmax (Tessitore et al., 2005; Randers et al., 2010). Another interesting finding was that the average HR and the time spent with HRs from 80% to 90% HRmax were further elevated during the football training carried out toward the end of the 16-week training period compared with the first week of training, ending up with an average heart rate of 84% HRmax. Also, the subjects engaged in additional minutes of game-play toward the end of the 16-week training period compared with the beginning of the IP, thus collectively, the subjects were able to endure an increased total training stimuli at the end of the training period. Taking into account that the aerobic fitness was markedly improved in the football group over the 16-week training period and that the HRs for walking and jogging at fixed treadmill speeds of 4 and 7 km/h were reduced by 8–14 bpm on average, the higher HRs during training clearly show that the training was intensified along the training period. Furthermore, there was no relationship between the HR response and the fitness level of the players as evaluated by VO2max and Yo-Yo IE1 performance, suggesting that the fitter players run the most and that additional running is beneficial for player involvement and performance. Together, these results emphasize that participation in small-sided football for untrained old men is resulting in a cardiovascular stimulus that is way above what is reached during everyday life activities, including physical activity, such as walking, bicycling, shopping, and gardening, and that this is the case both in the early phase and later on in a football intervention. In comparison, the HR during the

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Andersen et al. Table 1. Physiological response (VO2, %VO2max, ventilation, Respiratory Exchange Ratio, HR, %HRmax, blood lactate, and peak power output and time to exhaustion during maximal cycling testing) to submaximal and maximal exercise in elderly adults before (0 wks) and after 16 wks of football training (FG) or strength training (ST) or continuation of an inactive lifestyle (CO).

FG

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0 week Number of subjects 4.5 km/h walking Oxygen uptake (mL/min/kg) Oxygen uptake (%VO2max) Ventilation (L/min) Respiratory exchange ratio Heart rate (bpm) Heart rate (%HRmax) Blood lactate (mmol/L) 7.0 km/h jogging Oxygen uptake (mL/min/kg) Oxygen uptake (%VO2max) Ventilation (L/min) Respiratory exchange ratio Heart rate (bpm) Heart rate (%HRmax) Blood lactate (mmol/L) Maximal bicycle testing Oxygen uptake (mL/min/kg) Peak ventilation (L/min) Respiratory exchange ratio Heart rate (bpm) Blood lactate (mmol/L) Peak power output (W) Time-to-exhaustion (s)

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14.9 ± 1.2 52.2 ± 2.8 34 ± 3 0.78 ± 0.03 115 ± 6 67 ± 4 1.3 ± 0.1

14.8 ± 0.5 46.8 ± 2.4 31± 2 0.80 ± 0.02 101 ± 3*** 59 ± 2* 1.2 ± 0.1

15.8 ± 0.6 53.6 ± 4.0 37 ± 3 0.83 ± 0.02 109 ± 3 67 ± 3 1.4 ± 0.1

14.9 ± 0.6 48.8 ± 3.2 35 ± 2 0.80 ± 0.02 97 ± 3** 60 ± 3** 1.2 ± 0.1

16.7 ± 0.6 54.8 ± 3.3 38 ± 2 0.83 ± 0.04 105 ± 4 62 ± 3 1.5 ± 0.1

14.1 ± 0.9 49.7 ± 5.5 34 ± 3 0.83 ± 0.03 100 ± 3 59 ± 2 1.4 ± 0.1

22.9 ± 1.3 84.0 ± 3.7 67 ± 5 1.04 ± 0.05 154 ± 5 90 ± 3 5.4 ± 0.7****

26.9 ± 1.0 85.0 ± 2.8 71 ± 6 1.00 ± 0.04 146 ± 4* 85 ± 3* 3.8 ± 0.5**

25.9 ± 0.8 83.9 ± 4.8 81 ± 9 1.06 ± 0.03 150 ± 7 90 ± 5 3.5 ± 0.4

25.8 ± 0.8 82.7 ± 3.5 79 ± 8 0.98 ± 0.06 141 ± 6 85 ± 3 3.4 ± 0.5

26.2 ± 0.8 85.5 ± 2.3 76 ± 3 1.01 ± 0.02 146 ± 7 86 ± 3 4.7 ± 0.7

25.0 ± 0.8 82.1 ± 3.9 68 ± 4 0.99 ± 0.03 139 ± 4 83 ± 4 4.0 ± 0.7

28.2 ± 2.1 104 ± 4 1.11 ± 0.01 172 ± 3**** 9.6 ± 0.8 156 ± 6 751 ± 28

32.0 ± 1.9*** 110 ± 5 1.10 ± 0.03 167 ± 3 9.2 ± 0.9 167 ± 7 804 ± 36*

30.0 ± 1.8 115 ± 10 1.10 ± 0.01 161 ± 3 8.7 ± 0.4 180 ± 11 885 ± 61

30.8 ± 1.4 120 ± 11 1.06 ± 0.02 162 ± 4 8.1 ± 0.6 175 ± 10 842 ± 66

30.8 ± 1.2 119 ± 8 1.11 ± 0.03 170 ± 4 10.7 ± 1.1 180 ± 9 890 ± 48

30.1 ± 2.4 114 ± 13 1.10 ± 0.02 163 ± 3 8.4 ± 1.1 173 ± 11 832 ± 62

Means ± SEM are presented. *Significantly (P < 0.05) different from 0 wks. **Significantly (P < 0.01) different from 0 wks. ***Significantly (P < 0.001) different from 0 wks. ****FG different from ST (P < 0.05).

strength training was around 60% HRmax, with no time in the aerobic high-intensity zone, showing that the aerobic loading is of low-to-moderate intensity applying a limited cardiovascular stimulus (Bangsbo et al., 2006). The present study also evaluated the acute muscle and blood metabolite response during a football and strength training session performed at the end of IP. High blood lactates were observed for the football group, indicating periods with a high rate of anaerobic energy turnover derived from glycolysis, with even higher values for the strength training group. The average and peak blood lactate values were 4.6 and 7.2 mmol/L in the football group which is similar to or slightly lower than the values obtained in untrained young men during smallsided football (Randers et al., 2010; Brito et al., 2012). Corresponding values for the strength training group were 6.7 and 10.5 mmol/L with a fourfold increase in quadriceps muscle lactate during the strength training providing further evidence of a high anaerobic energy turnover. The quadriceps muscle glycogen breakdown during the 60-min training session was similar in the football and strength training group (101 and 92 mmol/kg dw) and comparable with that observed in untrained young men during a 1-h small-sided football session (118 mmol/kg dw) (Randers et al., 2010). Together these findings suggest a much higher aerobic metabolism and a somewhat lower anaerobic

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metabolism during football training than during strength training. The results of the present study revealed a large increase in plasma FFA (300 to 950 μmol/L) during the 60-min football training session, but no change during the strength training session. Previous studies have also observed increases in plasma FFA during and after small-sided training for young men (Krustrup et al., 2009) and in sub-elite football games (Krustrup et al., 2006), although the increases after 60 min of play were about two-thirds of the increase in the present study. The observed increase in FFA indicates an increase in muscle triglyceride oxidation and an elevated release of fatty acids from the adipose tissue, which is promoted when the blood flow to the adipose tissue is high when players are walking or standing. It is well established that catecholamine levels are elevated and that insulin levels are lowered during both football training and strength training (Bangsbo, 1994; Krustrup et al., 2006) which stimulates lipolysis resulting in an increase in plasma FFA (Stallknecht et al., 1995). However, the mobilization of fatty acids is inhibited by high lactate levels (Bulow & Madsen, 1981) which may in part explain the differences observed between the football and strength training groups, as the muscle lactate values appeared to be higher in the strength training group. Maximal oxygen uptake increased 3.9 mL/kg/min or 15% after 16 weeks of football training for the

Performance enhancements in veteran football 65–75-year-old subjects in the present study. This corresponds well with the 3–4 mL/kg/min changes previously reported after 12–16 weeks of recreational football training in untrained healthy men (Krustrup et al., 2009; Randers et al., 2010) and middle-aged men with hypertension or type 2 diabetes (Andersen et al., 2010; Knoepfli-Lenzin et al., 2010; Krustrup et al., 2013; Schmidt et al., 2013b). Notably, the observed improvement fully counteracts the age-related decline typically reported for time spans covering 10 years or more (Talbot et al., 2000). In contrast, the strength training group showed no change in aerobic power over the 16-week training period, which likely was explained by the low-to-moderate magnitude of cardiovascular strain imposed by this training modality, with average HRs of 100 bpm being insufficient of producing significant increases in maximal oxygen uptake (Krustrup et al., 2010). After 16 weeks of training, the football group showed a large improvement (43%) in intermittent exercise capacity as evaluated by the Yo-Yo IE1 test as well as a 7% increase in incremental exercise performance using a cycle ergometer test to exhaustion, whereas the strength training group and the control group had no changes in intermittent or continuous incremental exercise performance. Most activities of daily living and physical functions are of an intermittent nature, and the ability to perform physical exercise and quickly recover from these activities is of great importance for the elderly (Spirduso & Cronin, 2001). The mechanisms behind an increase in intermittent exercise performance of untrained individuals are multifactorial including improvements in maximal oxygen uptake, muscle oxidative capacity, running economy, anaerobic energy turnover, and muscle ion pumping (Mohr et al., 2007; Iaia et al., 2008). Again, studies in younger populations have shown similar effects of 12–16 weeks of recreational football on Yo-Yo IE performance (Krustrup et al., 2009). As no changes were observed in plasma potassium levels following training, as the strength training group demonstrated the highest peak blood lactate values with acute training while no changes were observed in running economy during treadmill running at 7 km/h for any of the intervention groups, it may be speculated that the above factors were not the primary causes of the present improvement in intermittent exercise performance following football training. Instead, it may be of importance that the football group had a large increase in maximal oxygen uptake and potentially also in muscle oxidative capacity. In a series of previous investigations, it has been shown that 12–16 weeks of recreational football training leads to elevated muscle oxidative enzyme activity and increased muscle capillarization in untrained men (Krustrup et al., 2009) and women (Bangsbo et al., 2010). A finding from the present study that points in this direction is the finding of lower blood lactate accumulation during treadmill

running at 7 km/h after compared with before the training intervention. However, further studies are warranted to fully understand the cause of improvements in intermittent exercise capacity after football training for aged subjects. Other important variables in relation to activities of daily living are the capacity for rapid muscle force (RFD) production and functional capacity, such as chair raising and stair walking ability (Leveille et al., 1999; Spirduso & Cronin, 2001). In the present study, the functional capacity was evaluated by the use of the STS test and the muscle power by the CMJ test. After 16 weeks of training, STS performance was markedly improved both in the football and the strength training group (29% and 26%, respectively), whereas the CMJ performance tended to be improved in both training groups as well. It is well documented that strength training is effective for improving contractile RFD both in middle-aged and elderly men (Aagaard et al., 2010). The present results provide further support to the notion that high-intensity strength training with heavy training loads and relatively few repetitions is a feasible and recommendable exercise modality in the elderly to improve muscle strength and functional capacity (Seynnes et al., 2004; Caserotti et al., 2008). Crosssectional studies have also provided evidence that the RFD and postural balance in old men with life-long participation in football are superior compared with age-matched inactive men (Sundstrup et al., 2010). Extending these observations, the present study is the first to demonstrate that short-term football training, to the same extend as can be observed with strength training, is effective in improving functional capacity in old men. The results of the CMJ test revealed a tendency for improvement in the two training groups (+16−18%) compared with the control group (−8%), but these changes did not reach significance. This may in part be due to the few participants in the present study and a large variation in the pre-post delta values in the CMJ test. However, recent studies have indicated that it takes somewhat longer to fully benefit from football or strength training in terms of improved jump performance (Krustrup et al., 2010; Randers et al., 2010; Jakobsen et al., 2012). Thus, positive effect on postural balance were observed after 12–16 weeks of football training, whereas muscle strength and jumping performance were significantly higher following 15–16 months of training compared with values recorded after 3–4 months of exercise training (Randers et al., 2010). In conclusion, short-term football training in untrained old men appears effective in improving aerobic fitness, as well as aerobically related intermittent and continuous exhaustive exercise performance. Also, football training appears effective in promoting functional ability to the same extent as can be seen with explosive-like strength training.

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Andersen et al. Perspectives Untrained old men with little or no prior experience of football can obtain a high training intensity by being involved in a motivating team sport, such as football, and the intensity of the training gradually increasing along with improvements in fitness. In small-sided football training, the HRs are high and there are periods of high anaerobic energy turnover and musculoskeletal impact, resulting in a greater training stimulus compared with everyday life activities, including physical activities, such as walking, bicycling, shopping, and gardening, and this is the case both in the early phase and later on in a football intervention. The present study showed that even short-term interventions with football training can result in changes in especially aerobic fitness, including aerobically related exercise performances during submaximal, intermittent, and continuous incremental exercise to exhaustion. Apparently, football training also has an ability to improve selected aspect of functional ability to the same extend as can be seen with strength training. Positive training adaptations in functional ability can indeed be obtained through strength training, although it can be recommended adding high-intensity endurance training or football training in order to achieve improvement in aerobic fitness and exhaustive exercise performance.

Despite the evident effectiveness of intense training in improving exercise performance and functional ability, caution should be taken toward engagement in such training modalities without prior clearance from a medical doctor. This was performed at the beginning of the present investigation. Also, we recommend modified rules to be adapted to the football training to minimize the risk of injuries, even though small-sided games has been proven to elicit a marked reduction in injury risk compared with actual football match-play (Krustrup et al., 2010), and as such, a structured supervised lead-in period to the training intervention should be considered. Key words: Training intensity, blood lactate, FFA, maximal oxygen uptake, Yo-Yo IE1 performance, CMJ, sit-to-stand.

Acknowledgements We would like to sincerely thank the participants in the study for their efforts. Also, the technical and practical assistance of Therese Hornstrup, Joshua Horton, Marie Von Hagman, and Mogens Theisen Pedersen is greatly appreciated. The study was supported by the FIFA Medical Assessment and Research Centre (F-MARC), The Danish Ministry of Culture (Kulturministeriets Udvalg for Idrætsforskning), and Nordea-fonden, Denmark.

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